drm/atomic_helper: duplicate state for drm_private_obj

Message ID 20200625115746.13396-1-shawnguo@kernel.org
State New
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  • drm/atomic_helper: duplicate state for drm_private_obj
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Commit Message

Shawn Guo June 25, 2020, 11:57 a.m.
From: Shawn Guo <shawn.guo@linaro.org>


The msm/mdp5 driver uses drm_private_obj as its global atomic state,
which keeps the assignment of hwpipe to plane.  With drm_private_obj
missing from duplicate state call, mdp5 suspend works with no problem
only for the very first time.  Any subsequent suspend will hit the
following warning, because hwpipe assignment doesn't get duplicated for
suspend state.  Adding drm_private_obj handling for duplicate state call
fixes the problem.

$ echo mem > /sys/power/state
[   38.111144] PM: suspend entry (deep)
[   38.111185] PM: Syncing filesystems ... done.
[   38.114630] Freezing user space processes ... (elapsed 0.001 seconds) done.
[   38.115912] OOM killer disabled.
[   38.115914] Freezing remaining freezable tasks ... (elapsed 0.001 seconds) done.
[   38.122170] ------------[ cut here ]------------
[   38.122212] WARNING: CPU: 0 PID: 1747 at drivers/gpu/drm/msm/disp/mdp5/mdp5_pipe.c:145 mdp5_pipe_release+0x90/0xc0
[   38.122215] Modules linked in:
[   38.122222] CPU: 0 PID: 1747 Comm: sh Not tainted 4.19.107-00515-g9d5e4d7a33ed-dirty #323
[   38.122224] Hardware name: Square, Inc. T2 Devkit (DT)
[   38.122228] pstate: 40000005 (nZcv daif -PAN -UAO)
[   38.122230] pc : mdp5_pipe_release+0x90/0xc0
[   38.122233] lr : mdp5_pipe_release+0x90/0xc0
[   38.122235] sp : ffff00000d13b7f0
[   38.122236] x29: ffff00000d13b7f0 x28: 0000000000000000
[   38.122240] x27: 0000000000000002 x26: ffff800079adce00
[   38.122243] x25: ffff800079405200 x24: 0000000000000000
[   38.122246] x23: ffff80007a78cc08 x22: ffff80007b1cc018
[   38.122249] x21: ffff80007b1cc000 x20: ffff80007b317080
[   38.122252] x19: ffff80007a78ce80 x18: 0000000000020000
[   38.122255] x17: 0000000000000000 x16: 0000000000000000
[   38.122258] x15: 00000000fffffff0 x14: ffff000008c3fb48
[   38.122261] x13: ffff000008cdac4a x12: ffff000008c3f000
[   38.122264] x11: 0000000000000000 x10: ffff000008cda000
[   38.122267] x9 : 0000000000000000 x8 : ffff000008ce4a40
[   38.122269] x7 : 0000000000000000 x6 : 0000000039ea41a9
[   38.122272] x5 : 0000000000000000 x4 : 0000000000000000
[   38.122275] x3 : ffffffffffffffff x2 : c7580c109cae4500
[   38.122278] x1 : 0000000000000000 x0 : 0000000000000024
[   38.122281] Call trace:
[   38.122285]  mdp5_pipe_release+0x90/0xc0
[   38.122288]  mdp5_plane_atomic_check+0x2c0/0x448
[   38.122294]  drm_atomic_helper_check_planes+0xd0/0x208
[   38.122298]  drm_atomic_helper_check+0x38/0xa8
[   38.122302]  drm_atomic_check_only+0x3e8/0x630
[   38.122305]  drm_atomic_commit+0x18/0x58
[   38.122309]  __drm_atomic_helper_disable_all.isra.12+0x15c/0x1a8
[   38.122312]  drm_atomic_helper_suspend+0x80/0xf0
[   38.122316]  msm_pm_suspend+0x4c/0x70
[   38.122320]  dpm_run_callback.isra.6+0x20/0x68
[   38.122323]  __device_suspend+0x110/0x308
[   38.122326]  dpm_suspend+0x100/0x1f0
[   38.122329]  dpm_suspend_start+0x64/0x70
[   38.122334]  suspend_devices_and_enter+0x110/0x500
[   38.122336]  pm_suspend+0x268/0x2c0
[   38.122339]  state_store+0x88/0x110
[   38.122345]  kobj_attr_store+0x14/0x28
[   38.122352]  sysfs_kf_write+0x3c/0x50
[   38.122355]  kernfs_fop_write+0x118/0x1e0
[   38.122360]  __vfs_write+0x30/0x168
[   38.122363]  vfs_write+0xa4/0x1a8
[   38.122366]  ksys_write+0x64/0xe8
[   38.122368]  __arm64_sys_write+0x18/0x20
[   38.122374]  el0_svc_common+0x6c/0x178
[   38.122377]  el0_svc_compat_handler+0x1c/0x28
[   38.122381]  el0_svc_compat+0x8/0x18
[   38.122383] ---[ end trace 24145b7d8545345b ]---
[   38.491552] Disabling non-boot CPUs ...

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>

---
 drivers/gpu/drm/drm_atomic_helper.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

-- 
2.17.1

Comments

Daniel Vetter June 25, 2020, 12:35 p.m. | #1
On Thu, Jun 25, 2020 at 1:58 PM Shawn Guo <shawnguo@kernel.org> wrote:
>
> From: Shawn Guo <shawn.guo@linaro.org>
>
> The msm/mdp5 driver uses drm_private_obj as its global atomic state,
> which keeps the assignment of hwpipe to plane.  With drm_private_obj
> missing from duplicate state call, mdp5 suspend works with no problem
> only for the very first time.  Any subsequent suspend will hit the
> following warning, because hwpipe assignment doesn't get duplicated for
> suspend state.  Adding drm_private_obj handling for duplicate state call
> fixes the problem.

If the driver needs a private state, it's supposed to duplicate that
in its atomic_check functionality. This isn't the helper's job.

If this is a bug in msm code, then pretty sure if you try hard enough,
you can hit the exact same bug from userspace too. Maybe good idea to
try and reproduce this with igt or something.
-Daniel


> $ echo mem > /sys/power/state
> [   38.111144] PM: suspend entry (deep)
> [   38.111185] PM: Syncing filesystems ... done.
> [   38.114630] Freezing user space processes ... (elapsed 0.001 seconds) done.
> [   38.115912] OOM killer disabled.
> [   38.115914] Freezing remaining freezable tasks ... (elapsed 0.001 seconds) done.
> [   38.122170] ------------[ cut here ]------------
> [   38.122212] WARNING: CPU: 0 PID: 1747 at drivers/gpu/drm/msm/disp/mdp5/mdp5_pipe.c:145 mdp5_pipe_release+0x90/0xc0
> [   38.122215] Modules linked in:
> [   38.122222] CPU: 0 PID: 1747 Comm: sh Not tainted 4.19.107-00515-g9d5e4d7a33ed-dirty #323
> [   38.122224] Hardware name: Square, Inc. T2 Devkit (DT)
> [   38.122228] pstate: 40000005 (nZcv daif -PAN -UAO)
> [   38.122230] pc : mdp5_pipe_release+0x90/0xc0
> [   38.122233] lr : mdp5_pipe_release+0x90/0xc0
> [   38.122235] sp : ffff00000d13b7f0
> [   38.122236] x29: ffff00000d13b7f0 x28: 0000000000000000
> [   38.122240] x27: 0000000000000002 x26: ffff800079adce00
> [   38.122243] x25: ffff800079405200 x24: 0000000000000000
> [   38.122246] x23: ffff80007a78cc08 x22: ffff80007b1cc018
> [   38.122249] x21: ffff80007b1cc000 x20: ffff80007b317080
> [   38.122252] x19: ffff80007a78ce80 x18: 0000000000020000
> [   38.122255] x17: 0000000000000000 x16: 0000000000000000
> [   38.122258] x15: 00000000fffffff0 x14: ffff000008c3fb48
> [   38.122261] x13: ffff000008cdac4a x12: ffff000008c3f000
> [   38.122264] x11: 0000000000000000 x10: ffff000008cda000
> [   38.122267] x9 : 0000000000000000 x8 : ffff000008ce4a40
> [   38.122269] x7 : 0000000000000000 x6 : 0000000039ea41a9
> [   38.122272] x5 : 0000000000000000 x4 : 0000000000000000
> [   38.122275] x3 : ffffffffffffffff x2 : c7580c109cae4500
> [   38.122278] x1 : 0000000000000000 x0 : 0000000000000024
> [   38.122281] Call trace:
> [   38.122285]  mdp5_pipe_release+0x90/0xc0
> [   38.122288]  mdp5_plane_atomic_check+0x2c0/0x448
> [   38.122294]  drm_atomic_helper_check_planes+0xd0/0x208
> [   38.122298]  drm_atomic_helper_check+0x38/0xa8
> [   38.122302]  drm_atomic_check_only+0x3e8/0x630
> [   38.122305]  drm_atomic_commit+0x18/0x58
> [   38.122309]  __drm_atomic_helper_disable_all.isra.12+0x15c/0x1a8
> [   38.122312]  drm_atomic_helper_suspend+0x80/0xf0
> [   38.122316]  msm_pm_suspend+0x4c/0x70
> [   38.122320]  dpm_run_callback.isra.6+0x20/0x68
> [   38.122323]  __device_suspend+0x110/0x308
> [   38.122326]  dpm_suspend+0x100/0x1f0
> [   38.122329]  dpm_suspend_start+0x64/0x70
> [   38.122334]  suspend_devices_and_enter+0x110/0x500
> [   38.122336]  pm_suspend+0x268/0x2c0
> [   38.122339]  state_store+0x88/0x110
> [   38.122345]  kobj_attr_store+0x14/0x28
> [   38.122352]  sysfs_kf_write+0x3c/0x50
> [   38.122355]  kernfs_fop_write+0x118/0x1e0
> [   38.122360]  __vfs_write+0x30/0x168
> [   38.122363]  vfs_write+0xa4/0x1a8
> [   38.122366]  ksys_write+0x64/0xe8
> [   38.122368]  __arm64_sys_write+0x18/0x20
> [   38.122374]  el0_svc_common+0x6c/0x178
> [   38.122377]  el0_svc_compat_handler+0x1c/0x28
> [   38.122381]  el0_svc_compat+0x8/0x18
> [   38.122383] ---[ end trace 24145b7d8545345b ]---
> [   38.491552] Disabling non-boot CPUs ...
>
> Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
> ---
>  drivers/gpu/drm/drm_atomic_helper.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index 85d163f16801..024985a92156 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -3140,6 +3140,7 @@ drm_atomic_helper_duplicate_state(struct drm_device *dev,
>         struct drm_atomic_state *state;
>         struct drm_connector *conn;
>         struct drm_connector_list_iter conn_iter;
> +       struct drm_private_obj *priv_obj;
>         struct drm_plane *plane;
>         struct drm_crtc *crtc;
>         int err = 0;
> @@ -3184,6 +3185,16 @@ drm_atomic_helper_duplicate_state(struct drm_device *dev,
>         }
>         drm_connector_list_iter_end(&conn_iter);
>
> +       drm_for_each_privobj(priv_obj, dev) {
> +               struct drm_private_state *priv_state;
> +
> +               priv_state = drm_atomic_get_private_obj_state(state, priv_obj);
> +               if (IS_ERR(priv_state)) {
> +                       err = PTR_ERR(priv_state);
> +                       goto free;
> +               }
> +       }
> +
>         /* clear the acquire context so that it isn't accidentally reused */
>         state->acquire_ctx = NULL;
>
> @@ -3278,6 +3289,8 @@ int drm_atomic_helper_commit_duplicated_state(struct drm_atomic_state *state,
>         struct drm_connector_state *new_conn_state;
>         struct drm_crtc *crtc;
>         struct drm_crtc_state *new_crtc_state;
> +       struct drm_private_state *new_priv_state;
> +       struct drm_private_obj *priv_obj;
>
>         state->acquire_ctx = ctx;
>
> @@ -3290,6 +3303,9 @@ int drm_atomic_helper_commit_duplicated_state(struct drm_atomic_state *state,
>         for_each_new_connector_in_state(state, connector, new_conn_state, i)
>                 state->connectors[i].old_state = connector->state;
>
> +       for_each_new_private_obj_in_state(state, priv_obj, new_priv_state, i)
> +               state->private_objs[i].old_state = priv_obj->state;
> +
>         ret = drm_atomic_commit(state);
>
>         state->acquire_ctx = NULL;
> --
> 2.17.1
>
Rob Clark June 25, 2020, 2:17 p.m. | #2
On Thu, Jun 25, 2020 at 5:35 AM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
>
> On Thu, Jun 25, 2020 at 1:58 PM Shawn Guo <shawnguo@kernel.org> wrote:
> >
> > From: Shawn Guo <shawn.guo@linaro.org>
> >
> > The msm/mdp5 driver uses drm_private_obj as its global atomic state,
> > which keeps the assignment of hwpipe to plane.  With drm_private_obj
> > missing from duplicate state call, mdp5 suspend works with no problem
> > only for the very first time.  Any subsequent suspend will hit the
> > following warning, because hwpipe assignment doesn't get duplicated for
> > suspend state.  Adding drm_private_obj handling for duplicate state call
> > fixes the problem.
>
> If the driver needs a private state, it's supposed to duplicate that
> in its atomic_check functionality. This isn't the helper's job.
>
> If this is a bug in msm code, then pretty sure if you try hard enough,
> you can hit the exact same bug from userspace too. Maybe good idea to
> try and reproduce this with igt or something.

The problem is how duplicate_state is used by the atomic
suspend/resume helpers.  They duplicate the running state on suspend,
forgetting to duplicate the global state.  Then everything is
disabled, the driver correctly duplicates and updates it's global
atomic state releasing the hwpipe.

But then on resume, we are re-applying plane state that thinks it
already has a hwpipe assigned (because that is part of the plane state
that was duplicated), without reapplying the matching global state.

On a normal atomic commit, we would duplicate the plane state that has
the hwpipe disabled, which would be in sync with the drivers global
state.  But since that is not what the atomic resume helper does, we
hit the situation where the plane state and the global state are out
of sync.

So the driver is dtrt, the problem really is with the helpers.  I
think this patch is the right thing to do.  It is incorrect for the
suspend/resume helpers to assume that they can re-apply duplicated
state without including the global state.

BR,
-R

> -Daniel
>
>
> > $ echo mem > /sys/power/state
> > [   38.111144] PM: suspend entry (deep)
> > [   38.111185] PM: Syncing filesystems ... done.
> > [   38.114630] Freezing user space processes ... (elapsed 0.001 seconds) done.
> > [   38.115912] OOM killer disabled.
> > [   38.115914] Freezing remaining freezable tasks ... (elapsed 0.001 seconds) done.
> > [   38.122170] ------------[ cut here ]------------
> > [   38.122212] WARNING: CPU: 0 PID: 1747 at drivers/gpu/drm/msm/disp/mdp5/mdp5_pipe.c:145 mdp5_pipe_release+0x90/0xc0
> > [   38.122215] Modules linked in:
> > [   38.122222] CPU: 0 PID: 1747 Comm: sh Not tainted 4.19.107-00515-g9d5e4d7a33ed-dirty #323
> > [   38.122224] Hardware name: Square, Inc. T2 Devkit (DT)
> > [   38.122228] pstate: 40000005 (nZcv daif -PAN -UAO)
> > [   38.122230] pc : mdp5_pipe_release+0x90/0xc0
> > [   38.122233] lr : mdp5_pipe_release+0x90/0xc0
> > [   38.122235] sp : ffff00000d13b7f0
> > [   38.122236] x29: ffff00000d13b7f0 x28: 0000000000000000
> > [   38.122240] x27: 0000000000000002 x26: ffff800079adce00
> > [   38.122243] x25: ffff800079405200 x24: 0000000000000000
> > [   38.122246] x23: ffff80007a78cc08 x22: ffff80007b1cc018
> > [   38.122249] x21: ffff80007b1cc000 x20: ffff80007b317080
> > [   38.122252] x19: ffff80007a78ce80 x18: 0000000000020000
> > [   38.122255] x17: 0000000000000000 x16: 0000000000000000
> > [   38.122258] x15: 00000000fffffff0 x14: ffff000008c3fb48
> > [   38.122261] x13: ffff000008cdac4a x12: ffff000008c3f000
> > [   38.122264] x11: 0000000000000000 x10: ffff000008cda000
> > [   38.122267] x9 : 0000000000000000 x8 : ffff000008ce4a40
> > [   38.122269] x7 : 0000000000000000 x6 : 0000000039ea41a9
> > [   38.122272] x5 : 0000000000000000 x4 : 0000000000000000
> > [   38.122275] x3 : ffffffffffffffff x2 : c7580c109cae4500
> > [   38.122278] x1 : 0000000000000000 x0 : 0000000000000024
> > [   38.122281] Call trace:
> > [   38.122285]  mdp5_pipe_release+0x90/0xc0
> > [   38.122288]  mdp5_plane_atomic_check+0x2c0/0x448
> > [   38.122294]  drm_atomic_helper_check_planes+0xd0/0x208
> > [   38.122298]  drm_atomic_helper_check+0x38/0xa8
> > [   38.122302]  drm_atomic_check_only+0x3e8/0x630
> > [   38.122305]  drm_atomic_commit+0x18/0x58
> > [   38.122309]  __drm_atomic_helper_disable_all.isra.12+0x15c/0x1a8
> > [   38.122312]  drm_atomic_helper_suspend+0x80/0xf0
> > [   38.122316]  msm_pm_suspend+0x4c/0x70
> > [   38.122320]  dpm_run_callback.isra.6+0x20/0x68
> > [   38.122323]  __device_suspend+0x110/0x308
> > [   38.122326]  dpm_suspend+0x100/0x1f0
> > [   38.122329]  dpm_suspend_start+0x64/0x70
> > [   38.122334]  suspend_devices_and_enter+0x110/0x500
> > [   38.122336]  pm_suspend+0x268/0x2c0
> > [   38.122339]  state_store+0x88/0x110
> > [   38.122345]  kobj_attr_store+0x14/0x28
> > [   38.122352]  sysfs_kf_write+0x3c/0x50
> > [   38.122355]  kernfs_fop_write+0x118/0x1e0
> > [   38.122360]  __vfs_write+0x30/0x168
> > [   38.122363]  vfs_write+0xa4/0x1a8
> > [   38.122366]  ksys_write+0x64/0xe8
> > [   38.122368]  __arm64_sys_write+0x18/0x20
> > [   38.122374]  el0_svc_common+0x6c/0x178
> > [   38.122377]  el0_svc_compat_handler+0x1c/0x28
> > [   38.122381]  el0_svc_compat+0x8/0x18
> > [   38.122383] ---[ end trace 24145b7d8545345b ]---
> > [   38.491552] Disabling non-boot CPUs ...
> >
> > Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
> > ---
> >  drivers/gpu/drm/drm_atomic_helper.c | 16 ++++++++++++++++
> >  1 file changed, 16 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> > index 85d163f16801..024985a92156 100644
> > --- a/drivers/gpu/drm/drm_atomic_helper.c
> > +++ b/drivers/gpu/drm/drm_atomic_helper.c
> > @@ -3140,6 +3140,7 @@ drm_atomic_helper_duplicate_state(struct drm_device *dev,
> >         struct drm_atomic_state *state;
> >         struct drm_connector *conn;
> >         struct drm_connector_list_iter conn_iter;
> > +       struct drm_private_obj *priv_obj;
> >         struct drm_plane *plane;
> >         struct drm_crtc *crtc;
> >         int err = 0;
> > @@ -3184,6 +3185,16 @@ drm_atomic_helper_duplicate_state(struct drm_device *dev,
> >         }
> >         drm_connector_list_iter_end(&conn_iter);
> >
> > +       drm_for_each_privobj(priv_obj, dev) {
> > +               struct drm_private_state *priv_state;
> > +
> > +               priv_state = drm_atomic_get_private_obj_state(state, priv_obj);
> > +               if (IS_ERR(priv_state)) {
> > +                       err = PTR_ERR(priv_state);
> > +                       goto free;
> > +               }
> > +       }
> > +
> >         /* clear the acquire context so that it isn't accidentally reused */
> >         state->acquire_ctx = NULL;
> >
> > @@ -3278,6 +3289,8 @@ int drm_atomic_helper_commit_duplicated_state(struct drm_atomic_state *state,
> >         struct drm_connector_state *new_conn_state;
> >         struct drm_crtc *crtc;
> >         struct drm_crtc_state *new_crtc_state;
> > +       struct drm_private_state *new_priv_state;
> > +       struct drm_private_obj *priv_obj;
> >
> >         state->acquire_ctx = ctx;
> >
> > @@ -3290,6 +3303,9 @@ int drm_atomic_helper_commit_duplicated_state(struct drm_atomic_state *state,
> >         for_each_new_connector_in_state(state, connector, new_conn_state, i)
> >                 state->connectors[i].old_state = connector->state;
> >
> > +       for_each_new_private_obj_in_state(state, priv_obj, new_priv_state, i)
> > +               state->private_objs[i].old_state = priv_obj->state;
> > +
> >         ret = drm_atomic_commit(state);
> >
> >         state->acquire_ctx = NULL;
> > --
> > 2.17.1
> >
>
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch
Daniel Vetter June 25, 2020, 3:54 p.m. | #3
On Thu, Jun 25, 2020 at 4:17 PM Rob Clark <robdclark@gmail.com> wrote:
>

> On Thu, Jun 25, 2020 at 5:35 AM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:

> >

> > On Thu, Jun 25, 2020 at 1:58 PM Shawn Guo <shawnguo@kernel.org> wrote:

> > >

> > > From: Shawn Guo <shawn.guo@linaro.org>

> > >

> > > The msm/mdp5 driver uses drm_private_obj as its global atomic state,

> > > which keeps the assignment of hwpipe to plane.  With drm_private_obj

> > > missing from duplicate state call, mdp5 suspend works with no problem

> > > only for the very first time.  Any subsequent suspend will hit the

> > > following warning, because hwpipe assignment doesn't get duplicated for

> > > suspend state.  Adding drm_private_obj handling for duplicate state call

> > > fixes the problem.

> >

> > If the driver needs a private state, it's supposed to duplicate that

> > in its atomic_check functionality. This isn't the helper's job.

> >

> > If this is a bug in msm code, then pretty sure if you try hard enough,

> > you can hit the exact same bug from userspace too. Maybe good idea to

> > try and reproduce this with igt or something.

>

> The problem is how duplicate_state is used by the atomic

> suspend/resume helpers.  They duplicate the running state on suspend,

> forgetting to duplicate the global state.  Then everything is

> disabled, the driver correctly duplicates and updates it's global

> atomic state releasing the hwpipe.

>

> But then on resume, we are re-applying plane state that thinks it

> already has a hwpipe assigned (because that is part of the plane state

> that was duplicated), without reapplying the matching global state.

>

> On a normal atomic commit, we would duplicate the plane state that has

> the hwpipe disabled, which would be in sync with the drivers global

> state.  But since that is not what the atomic resume helper does, we

> hit the situation where the plane state and the global state are out

> of sync.

>

> So the driver is dtrt, the problem really is with the helpers.  I

> think this patch is the right thing to do.  It is incorrect for the

> suspend/resume helpers to assume that they can re-apply duplicated

> state without including the global state.


Hm, this is a bit awkward. Generally the assumption is that you should
be recomputing the derived state (like hwpipe) no matter what. If your
driver doesn't do that, then all kinds of things can leak from the
pre-resume to the post-resume side of things, that's kinda why I'm not
thrilled with this patch, I think it has good potential to open up a
can of worms. Iirc this patch has come up in the past, and in those
cases it was a driver bug.

For this case, why is msm reusing a hw pipe assignment of a disabled plane?

Unfortunately we can't copy the drm state into the overall structure
to solve this, since that would miss driver-private properties. So
unfortunately we can't make this match a real atomic commit from
userspace perfectly.

Another option would be if msm just copies the private state it needs
to not go boom.

Doing this unconditionally might break other drivers that rely on
private state not being duplicated, but I guess that would also be
somewhat of a driver bug.
-Daniel

>

> BR,

> -R

>

> > -Daniel

> >

> >

> > > $ echo mem > /sys/power/state

> > > [   38.111144] PM: suspend entry (deep)

> > > [   38.111185] PM: Syncing filesystems ... done.

> > > [   38.114630] Freezing user space processes ... (elapsed 0.001 seconds) done.

> > > [   38.115912] OOM killer disabled.

> > > [   38.115914] Freezing remaining freezable tasks ... (elapsed 0.001 seconds) done.

> > > [   38.122170] ------------[ cut here ]------------

> > > [   38.122212] WARNING: CPU: 0 PID: 1747 at drivers/gpu/drm/msm/disp/mdp5/mdp5_pipe.c:145 mdp5_pipe_release+0x90/0xc0

> > > [   38.122215] Modules linked in:

> > > [   38.122222] CPU: 0 PID: 1747 Comm: sh Not tainted 4.19.107-00515-g9d5e4d7a33ed-dirty #323

> > > [   38.122224] Hardware name: Square, Inc. T2 Devkit (DT)

> > > [   38.122228] pstate: 40000005 (nZcv daif -PAN -UAO)

> > > [   38.122230] pc : mdp5_pipe_release+0x90/0xc0

> > > [   38.122233] lr : mdp5_pipe_release+0x90/0xc0

> > > [   38.122235] sp : ffff00000d13b7f0

> > > [   38.122236] x29: ffff00000d13b7f0 x28: 0000000000000000

> > > [   38.122240] x27: 0000000000000002 x26: ffff800079adce00

> > > [   38.122243] x25: ffff800079405200 x24: 0000000000000000

> > > [   38.122246] x23: ffff80007a78cc08 x22: ffff80007b1cc018

> > > [   38.122249] x21: ffff80007b1cc000 x20: ffff80007b317080

> > > [   38.122252] x19: ffff80007a78ce80 x18: 0000000000020000

> > > [   38.122255] x17: 0000000000000000 x16: 0000000000000000

> > > [   38.122258] x15: 00000000fffffff0 x14: ffff000008c3fb48

> > > [   38.122261] x13: ffff000008cdac4a x12: ffff000008c3f000

> > > [   38.122264] x11: 0000000000000000 x10: ffff000008cda000

> > > [   38.122267] x9 : 0000000000000000 x8 : ffff000008ce4a40

> > > [   38.122269] x7 : 0000000000000000 x6 : 0000000039ea41a9

> > > [   38.122272] x5 : 0000000000000000 x4 : 0000000000000000

> > > [   38.122275] x3 : ffffffffffffffff x2 : c7580c109cae4500

> > > [   38.122278] x1 : 0000000000000000 x0 : 0000000000000024

> > > [   38.122281] Call trace:

> > > [   38.122285]  mdp5_pipe_release+0x90/0xc0

> > > [   38.122288]  mdp5_plane_atomic_check+0x2c0/0x448

> > > [   38.122294]  drm_atomic_helper_check_planes+0xd0/0x208

> > > [   38.122298]  drm_atomic_helper_check+0x38/0xa8

> > > [   38.122302]  drm_atomic_check_only+0x3e8/0x630

> > > [   38.122305]  drm_atomic_commit+0x18/0x58

> > > [   38.122309]  __drm_atomic_helper_disable_all.isra.12+0x15c/0x1a8

> > > [   38.122312]  drm_atomic_helper_suspend+0x80/0xf0

> > > [   38.122316]  msm_pm_suspend+0x4c/0x70

> > > [   38.122320]  dpm_run_callback.isra.6+0x20/0x68

> > > [   38.122323]  __device_suspend+0x110/0x308

> > > [   38.122326]  dpm_suspend+0x100/0x1f0

> > > [   38.122329]  dpm_suspend_start+0x64/0x70

> > > [   38.122334]  suspend_devices_and_enter+0x110/0x500

> > > [   38.122336]  pm_suspend+0x268/0x2c0

> > > [   38.122339]  state_store+0x88/0x110

> > > [   38.122345]  kobj_attr_store+0x14/0x28

> > > [   38.122352]  sysfs_kf_write+0x3c/0x50

> > > [   38.122355]  kernfs_fop_write+0x118/0x1e0

> > > [   38.122360]  __vfs_write+0x30/0x168

> > > [   38.122363]  vfs_write+0xa4/0x1a8

> > > [   38.122366]  ksys_write+0x64/0xe8

> > > [   38.122368]  __arm64_sys_write+0x18/0x20

> > > [   38.122374]  el0_svc_common+0x6c/0x178

> > > [   38.122377]  el0_svc_compat_handler+0x1c/0x28

> > > [   38.122381]  el0_svc_compat+0x8/0x18

> > > [   38.122383] ---[ end trace 24145b7d8545345b ]---

> > > [   38.491552] Disabling non-boot CPUs ...

> > >

> > > Signed-off-by: Shawn Guo <shawn.guo@linaro.org>

> > > ---

> > >  drivers/gpu/drm/drm_atomic_helper.c | 16 ++++++++++++++++

> > >  1 file changed, 16 insertions(+)

> > >

> > > diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c

> > > index 85d163f16801..024985a92156 100644

> > > --- a/drivers/gpu/drm/drm_atomic_helper.c

> > > +++ b/drivers/gpu/drm/drm_atomic_helper.c

> > > @@ -3140,6 +3140,7 @@ drm_atomic_helper_duplicate_state(struct drm_device *dev,

> > >         struct drm_atomic_state *state;

> > >         struct drm_connector *conn;

> > >         struct drm_connector_list_iter conn_iter;

> > > +       struct drm_private_obj *priv_obj;

> > >         struct drm_plane *plane;

> > >         struct drm_crtc *crtc;

> > >         int err = 0;

> > > @@ -3184,6 +3185,16 @@ drm_atomic_helper_duplicate_state(struct drm_device *dev,

> > >         }

> > >         drm_connector_list_iter_end(&conn_iter);

> > >

> > > +       drm_for_each_privobj(priv_obj, dev) {

> > > +               struct drm_private_state *priv_state;

> > > +

> > > +               priv_state = drm_atomic_get_private_obj_state(state, priv_obj);

> > > +               if (IS_ERR(priv_state)) {

> > > +                       err = PTR_ERR(priv_state);

> > > +                       goto free;

> > > +               }

> > > +       }

> > > +

> > >         /* clear the acquire context so that it isn't accidentally reused */

> > >         state->acquire_ctx = NULL;

> > >

> > > @@ -3278,6 +3289,8 @@ int drm_atomic_helper_commit_duplicated_state(struct drm_atomic_state *state,

> > >         struct drm_connector_state *new_conn_state;

> > >         struct drm_crtc *crtc;

> > >         struct drm_crtc_state *new_crtc_state;

> > > +       struct drm_private_state *new_priv_state;

> > > +       struct drm_private_obj *priv_obj;

> > >

> > >         state->acquire_ctx = ctx;

> > >

> > > @@ -3290,6 +3303,9 @@ int drm_atomic_helper_commit_duplicated_state(struct drm_atomic_state *state,

> > >         for_each_new_connector_in_state(state, connector, new_conn_state, i)

> > >                 state->connectors[i].old_state = connector->state;

> > >

> > > +       for_each_new_private_obj_in_state(state, priv_obj, new_priv_state, i)

> > > +               state->private_objs[i].old_state = priv_obj->state;

> > > +

> > >         ret = drm_atomic_commit(state);

> > >

> > >         state->acquire_ctx = NULL;

> > > --

> > > 2.17.1

> > >

> >

> >

> > --

> > Daniel Vetter

> > Software Engineer, Intel Corporation

> > http://blog.ffwll.ch




-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
Rob Clark June 25, 2020, 4:24 p.m. | #4
On Thu, Jun 25, 2020 at 8:55 AM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
>

> On Thu, Jun 25, 2020 at 4:17 PM Rob Clark <robdclark@gmail.com> wrote:

> >

> > On Thu, Jun 25, 2020 at 5:35 AM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:

> > >

> > > On Thu, Jun 25, 2020 at 1:58 PM Shawn Guo <shawnguo@kernel.org> wrote:

> > > >

> > > > From: Shawn Guo <shawn.guo@linaro.org>

> > > >

> > > > The msm/mdp5 driver uses drm_private_obj as its global atomic state,

> > > > which keeps the assignment of hwpipe to plane.  With drm_private_obj

> > > > missing from duplicate state call, mdp5 suspend works with no problem

> > > > only for the very first time.  Any subsequent suspend will hit the

> > > > following warning, because hwpipe assignment doesn't get duplicated for

> > > > suspend state.  Adding drm_private_obj handling for duplicate state call

> > > > fixes the problem.

> > >

> > > If the driver needs a private state, it's supposed to duplicate that

> > > in its atomic_check functionality. This isn't the helper's job.

> > >

> > > If this is a bug in msm code, then pretty sure if you try hard enough,

> > > you can hit the exact same bug from userspace too. Maybe good idea to

> > > try and reproduce this with igt or something.

> >

> > The problem is how duplicate_state is used by the atomic

> > suspend/resume helpers.  They duplicate the running state on suspend,

> > forgetting to duplicate the global state.  Then everything is

> > disabled, the driver correctly duplicates and updates it's global

> > atomic state releasing the hwpipe.

> >

> > But then on resume, we are re-applying plane state that thinks it

> > already has a hwpipe assigned (because that is part of the plane state

> > that was duplicated), without reapplying the matching global state.

> >

> > On a normal atomic commit, we would duplicate the plane state that has

> > the hwpipe disabled, which would be in sync with the drivers global

> > state.  But since that is not what the atomic resume helper does, we

> > hit the situation where the plane state and the global state are out

> > of sync.

> >

> > So the driver is dtrt, the problem really is with the helpers.  I

> > think this patch is the right thing to do.  It is incorrect for the

> > suspend/resume helpers to assume that they can re-apply duplicated

> > state without including the global state.

>

> Hm, this is a bit awkward. Generally the assumption is that you should

> be recomputing the derived state (like hwpipe) no matter what. If your

> driver doesn't do that, then all kinds of things can leak from the

> pre-resume to the post-resume side of things, that's kinda why I'm not

> thrilled with this patch, I think it has good potential to open up a

> can of worms. Iirc this patch has come up in the past, and in those

> cases it was a driver bug.

>

> For this case, why is msm reusing a hw pipe assignment of a disabled plane?


Because it is part of the plane state that is being restored.

Since resume uses the old state saved before the
drm_atomic_helper_disable_all(), rather than duplicating the current
state, we end up with this mismatch between global and plane state.  I
think stashing away the old state is probably ok, but we can't just do
it piecemeal without including the global state.

I suppose part of the problem is the hwpipe (and other such
dynamically assigned resources) touch both private and plane (and
crtc) state.  The global state object knows which resources are
assigned to which plane/crtc.  But the plane/crtc state knows which of
the (potentially) two hwpipe/mixers is "left" (primary) and "right"
(secondary).

>

> Unfortunately we can't copy the drm state into the overall structure

> to solve this, since that would miss driver-private properties. So

> unfortunately we can't make this match a real atomic commit from

> userspace perfectly.


I'm not sure I understand this?  The driver private properties
would/should be part of one of the state objs (plane/crtc/global)?  If
the atomic state (including global) represents the entirety of the hw
state, you should be able to stash off N different versions of them
and re-apply them in any order you want because they are all
self-consistent.

>

> Another option would be if msm just copies the private state it needs

> to not go boom.

>

> Doing this unconditionally might break other drivers that rely on

> private state not being duplicated, but I guess that would also be

> somewhat of a driver bug.


I guess we could duplicate our own version of
drm_atomic_helper_suspend().. or maybe add a 'duplicate_global' param
to drm_atomic_helper_suspend().

I'm not too sure how many drivers these days are using global atomic
state, so not sure how many would be potentially broken, but opting in
to duplicating global state seems reasonable if necessary.

BR,
-R

> -Daniel

>

> >

> > BR,

> > -R

> >

> > > -Daniel

> > >

> > >

> > > > $ echo mem > /sys/power/state

> > > > [   38.111144] PM: suspend entry (deep)

> > > > [   38.111185] PM: Syncing filesystems ... done.

> > > > [   38.114630] Freezing user space processes ... (elapsed 0.001 seconds) done.

> > > > [   38.115912] OOM killer disabled.

> > > > [   38.115914] Freezing remaining freezable tasks ... (elapsed 0.001 seconds) done.

> > > > [   38.122170] ------------[ cut here ]------------

> > > > [   38.122212] WARNING: CPU: 0 PID: 1747 at drivers/gpu/drm/msm/disp/mdp5/mdp5_pipe.c:145 mdp5_pipe_release+0x90/0xc0

> > > > [   38.122215] Modules linked in:

> > > > [   38.122222] CPU: 0 PID: 1747 Comm: sh Not tainted 4.19.107-00515-g9d5e4d7a33ed-dirty #323

> > > > [   38.122224] Hardware name: Square, Inc. T2 Devkit (DT)

> > > > [   38.122228] pstate: 40000005 (nZcv daif -PAN -UAO)

> > > > [   38.122230] pc : mdp5_pipe_release+0x90/0xc0

> > > > [   38.122233] lr : mdp5_pipe_release+0x90/0xc0

> > > > [   38.122235] sp : ffff00000d13b7f0

> > > > [   38.122236] x29: ffff00000d13b7f0 x28: 0000000000000000

> > > > [   38.122240] x27: 0000000000000002 x26: ffff800079adce00

> > > > [   38.122243] x25: ffff800079405200 x24: 0000000000000000

> > > > [   38.122246] x23: ffff80007a78cc08 x22: ffff80007b1cc018

> > > > [   38.122249] x21: ffff80007b1cc000 x20: ffff80007b317080

> > > > [   38.122252] x19: ffff80007a78ce80 x18: 0000000000020000

> > > > [   38.122255] x17: 0000000000000000 x16: 0000000000000000

> > > > [   38.122258] x15: 00000000fffffff0 x14: ffff000008c3fb48

> > > > [   38.122261] x13: ffff000008cdac4a x12: ffff000008c3f000

> > > > [   38.122264] x11: 0000000000000000 x10: ffff000008cda000

> > > > [   38.122267] x9 : 0000000000000000 x8 : ffff000008ce4a40

> > > > [   38.122269] x7 : 0000000000000000 x6 : 0000000039ea41a9

> > > > [   38.122272] x5 : 0000000000000000 x4 : 0000000000000000

> > > > [   38.122275] x3 : ffffffffffffffff x2 : c7580c109cae4500

> > > > [   38.122278] x1 : 0000000000000000 x0 : 0000000000000024

> > > > [   38.122281] Call trace:

> > > > [   38.122285]  mdp5_pipe_release+0x90/0xc0

> > > > [   38.122288]  mdp5_plane_atomic_check+0x2c0/0x448

> > > > [   38.122294]  drm_atomic_helper_check_planes+0xd0/0x208

> > > > [   38.122298]  drm_atomic_helper_check+0x38/0xa8

> > > > [   38.122302]  drm_atomic_check_only+0x3e8/0x630

> > > > [   38.122305]  drm_atomic_commit+0x18/0x58

> > > > [   38.122309]  __drm_atomic_helper_disable_all.isra.12+0x15c/0x1a8

> > > > [   38.122312]  drm_atomic_helper_suspend+0x80/0xf0

> > > > [   38.122316]  msm_pm_suspend+0x4c/0x70

> > > > [   38.122320]  dpm_run_callback.isra.6+0x20/0x68

> > > > [   38.122323]  __device_suspend+0x110/0x308

> > > > [   38.122326]  dpm_suspend+0x100/0x1f0

> > > > [   38.122329]  dpm_suspend_start+0x64/0x70

> > > > [   38.122334]  suspend_devices_and_enter+0x110/0x500

> > > > [   38.122336]  pm_suspend+0x268/0x2c0

> > > > [   38.122339]  state_store+0x88/0x110

> > > > [   38.122345]  kobj_attr_store+0x14/0x28

> > > > [   38.122352]  sysfs_kf_write+0x3c/0x50

> > > > [   38.122355]  kernfs_fop_write+0x118/0x1e0

> > > > [   38.122360]  __vfs_write+0x30/0x168

> > > > [   38.122363]  vfs_write+0xa4/0x1a8

> > > > [   38.122366]  ksys_write+0x64/0xe8

> > > > [   38.122368]  __arm64_sys_write+0x18/0x20

> > > > [   38.122374]  el0_svc_common+0x6c/0x178

> > > > [   38.122377]  el0_svc_compat_handler+0x1c/0x28

> > > > [   38.122381]  el0_svc_compat+0x8/0x18

> > > > [   38.122383] ---[ end trace 24145b7d8545345b ]---

> > > > [   38.491552] Disabling non-boot CPUs ...

> > > >

> > > > Signed-off-by: Shawn Guo <shawn.guo@linaro.org>

> > > > ---

> > > >  drivers/gpu/drm/drm_atomic_helper.c | 16 ++++++++++++++++

> > > >  1 file changed, 16 insertions(+)

> > > >

> > > > diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c

> > > > index 85d163f16801..024985a92156 100644

> > > > --- a/drivers/gpu/drm/drm_atomic_helper.c

> > > > +++ b/drivers/gpu/drm/drm_atomic_helper.c

> > > > @@ -3140,6 +3140,7 @@ drm_atomic_helper_duplicate_state(struct drm_device *dev,

> > > >         struct drm_atomic_state *state;

> > > >         struct drm_connector *conn;

> > > >         struct drm_connector_list_iter conn_iter;

> > > > +       struct drm_private_obj *priv_obj;

> > > >         struct drm_plane *plane;

> > > >         struct drm_crtc *crtc;

> > > >         int err = 0;

> > > > @@ -3184,6 +3185,16 @@ drm_atomic_helper_duplicate_state(struct drm_device *dev,

> > > >         }

> > > >         drm_connector_list_iter_end(&conn_iter);

> > > >

> > > > +       drm_for_each_privobj(priv_obj, dev) {

> > > > +               struct drm_private_state *priv_state;

> > > > +

> > > > +               priv_state = drm_atomic_get_private_obj_state(state, priv_obj);

> > > > +               if (IS_ERR(priv_state)) {

> > > > +                       err = PTR_ERR(priv_state);

> > > > +                       goto free;

> > > > +               }

> > > > +       }

> > > > +

> > > >         /* clear the acquire context so that it isn't accidentally reused */

> > > >         state->acquire_ctx = NULL;

> > > >

> > > > @@ -3278,6 +3289,8 @@ int drm_atomic_helper_commit_duplicated_state(struct drm_atomic_state *state,

> > > >         struct drm_connector_state *new_conn_state;

> > > >         struct drm_crtc *crtc;

> > > >         struct drm_crtc_state *new_crtc_state;

> > > > +       struct drm_private_state *new_priv_state;

> > > > +       struct drm_private_obj *priv_obj;

> > > >

> > > >         state->acquire_ctx = ctx;

> > > >

> > > > @@ -3290,6 +3303,9 @@ int drm_atomic_helper_commit_duplicated_state(struct drm_atomic_state *state,

> > > >         for_each_new_connector_in_state(state, connector, new_conn_state, i)

> > > >                 state->connectors[i].old_state = connector->state;

> > > >

> > > > +       for_each_new_private_obj_in_state(state, priv_obj, new_priv_state, i)

> > > > +               state->private_objs[i].old_state = priv_obj->state;

> > > > +

> > > >         ret = drm_atomic_commit(state);

> > > >

> > > >         state->acquire_ctx = NULL;

> > > > --

> > > > 2.17.1

> > > >

> > >

> > >

> > > --

> > > Daniel Vetter

> > > Software Engineer, Intel Corporation

> > > http://blog.ffwll.ch

>

>

>

> --

> Daniel Vetter

> Software Engineer, Intel Corporation

> http://blog.ffwll.ch
Daniel Vetter June 26, 2020, 1:46 p.m. | #5
On Thu, Jun 25, 2020 at 09:24:38AM -0700, Rob Clark wrote:
> On Thu, Jun 25, 2020 at 8:55 AM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:

> >

> > On Thu, Jun 25, 2020 at 4:17 PM Rob Clark <robdclark@gmail.com> wrote:

> > >

> > > On Thu, Jun 25, 2020 at 5:35 AM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:

> > > >

> > > > On Thu, Jun 25, 2020 at 1:58 PM Shawn Guo <shawnguo@kernel.org> wrote:

> > > > >

> > > > > From: Shawn Guo <shawn.guo@linaro.org>

> > > > >

> > > > > The msm/mdp5 driver uses drm_private_obj as its global atomic state,

> > > > > which keeps the assignment of hwpipe to plane.  With drm_private_obj

> > > > > missing from duplicate state call, mdp5 suspend works with no problem

> > > > > only for the very first time.  Any subsequent suspend will hit the

> > > > > following warning, because hwpipe assignment doesn't get duplicated for

> > > > > suspend state.  Adding drm_private_obj handling for duplicate state call

> > > > > fixes the problem.

> > > >

> > > > If the driver needs a private state, it's supposed to duplicate that

> > > > in its atomic_check functionality. This isn't the helper's job.

> > > >

> > > > If this is a bug in msm code, then pretty sure if you try hard enough,

> > > > you can hit the exact same bug from userspace too. Maybe good idea to

> > > > try and reproduce this with igt or something.

> > >

> > > The problem is how duplicate_state is used by the atomic

> > > suspend/resume helpers.  They duplicate the running state on suspend,

> > > forgetting to duplicate the global state.  Then everything is

> > > disabled, the driver correctly duplicates and updates it's global

> > > atomic state releasing the hwpipe.

> > >

> > > But then on resume, we are re-applying plane state that thinks it

> > > already has a hwpipe assigned (because that is part of the plane state

> > > that was duplicated), without reapplying the matching global state.

> > >

> > > On a normal atomic commit, we would duplicate the plane state that has

> > > the hwpipe disabled, which would be in sync with the drivers global

> > > state.  But since that is not what the atomic resume helper does, we

> > > hit the situation where the plane state and the global state are out

> > > of sync.

> > >

> > > So the driver is dtrt, the problem really is with the helpers.  I

> > > think this patch is the right thing to do.  It is incorrect for the

> > > suspend/resume helpers to assume that they can re-apply duplicated

> > > state without including the global state.

> >

> > Hm, this is a bit awkward. Generally the assumption is that you should

> > be recomputing the derived state (like hwpipe) no matter what. If your

> > driver doesn't do that, then all kinds of things can leak from the

> > pre-resume to the post-resume side of things, that's kinda why I'm not

> > thrilled with this patch, I think it has good potential to open up a

> > can of worms. Iirc this patch has come up in the past, and in those

> > cases it was a driver bug.

> >

> > For this case, why is msm reusing a hw pipe assignment of a disabled plane?

> 

> Because it is part of the plane state that is being restored.

> 

> Since resume uses the old state saved before the

> drm_atomic_helper_disable_all(), rather than duplicating the current

> state, we end up with this mismatch between global and plane state.  I

> think stashing away the old state is probably ok, but we can't just do

> it piecemeal without including the global state.

> 

> I suppose part of the problem is the hwpipe (and other such

> dynamically assigned resources) touch both private and plane (and

> crtc) state.  The global state object knows which resources are

> assigned to which plane/crtc.  But the plane/crtc state knows which of

> the (potentially) two hwpipe/mixers is "left" (primary) and "right"

> (secondary).


Yeah I get all that, what I meant is: Why don't you just blindly recompute
the hwpipe assignment every time a full modeset is done? Caching it for
pure plane flips makes sense, but drm_crtc_needs_modset == true and just
throw it all overboard and assign new ones I think would also solve this
problem. Since the hwpipe global state would indicate that all pipes are
unallocated that should work (I hope).

Imo just recomputing state is a good atomic pattern, it avoids drivers
getting stuck in a corner somewhere you can't reset them out of anymore.

My question here was, why can't you do that?

> > Unfortunately we can't copy the drm state into the overall structure

> > to solve this, since that would miss driver-private properties. So

> > unfortunately we can't make this match a real atomic commit from

> > userspace perfectly.

> 

> I'm not sure I understand this?  The driver private properties

> would/should be part of one of the state objs (plane/crtc/global)?  If

> the atomic state (including global) represents the entirety of the hw

> state, you should be able to stash off N different versions of them

> and re-apply them in any order you want because they are all

> self-consistent.


So for normal atomic commit we have:

1. duplicate current state
2. set properties

But for resume helpers it's some random older state, so the expectations
break a bit. We could approximate that using something like:

1. duplicate current state into curr_state
2. set properties using a memcpy of the drm core state structure, leaving
the driver private stuff as-is.

But a) there's also some non-property state in drm state structures and b)
properties which are driver extensions and set into the driver part of the
state would get lost.

So also not great.

> > Another option would be if msm just copies the private state it needs

> > to not go boom.

> >

> > Doing this unconditionally might break other drivers that rely on

> > private state not being duplicated, but I guess that would also be

> > somewhat of a driver bug.

> 

> I guess we could duplicate our own version of

> drm_atomic_helper_suspend().. or maybe add a 'duplicate_global' param

> to drm_atomic_helper_suspend().

> 

> I'm not too sure how many drivers these days are using global atomic

> state, so not sure how many would be potentially broken, but opting in

> to duplicating global state seems reasonable if necessary.


dp mst uses it to track it's stuff at least, and I think it's spreading
quite a bit into drivers using them to track all kinds of things, not just
a single global state.
-Daniel

> 

> BR,

> -R

> 

> > -Daniel

> >

> > >

> > > BR,

> > > -R

> > >

> > > > -Daniel

> > > >

> > > >

> > > > > $ echo mem > /sys/power/state

> > > > > [   38.111144] PM: suspend entry (deep)

> > > > > [   38.111185] PM: Syncing filesystems ... done.

> > > > > [   38.114630] Freezing user space processes ... (elapsed 0.001 seconds) done.

> > > > > [   38.115912] OOM killer disabled.

> > > > > [   38.115914] Freezing remaining freezable tasks ... (elapsed 0.001 seconds) done.

> > > > > [   38.122170] ------------[ cut here ]------------

> > > > > [   38.122212] WARNING: CPU: 0 PID: 1747 at drivers/gpu/drm/msm/disp/mdp5/mdp5_pipe.c:145 mdp5_pipe_release+0x90/0xc0

> > > > > [   38.122215] Modules linked in:

> > > > > [   38.122222] CPU: 0 PID: 1747 Comm: sh Not tainted 4.19.107-00515-g9d5e4d7a33ed-dirty #323

> > > > > [   38.122224] Hardware name: Square, Inc. T2 Devkit (DT)

> > > > > [   38.122228] pstate: 40000005 (nZcv daif -PAN -UAO)

> > > > > [   38.122230] pc : mdp5_pipe_release+0x90/0xc0

> > > > > [   38.122233] lr : mdp5_pipe_release+0x90/0xc0

> > > > > [   38.122235] sp : ffff00000d13b7f0

> > > > > [   38.122236] x29: ffff00000d13b7f0 x28: 0000000000000000

> > > > > [   38.122240] x27: 0000000000000002 x26: ffff800079adce00

> > > > > [   38.122243] x25: ffff800079405200 x24: 0000000000000000

> > > > > [   38.122246] x23: ffff80007a78cc08 x22: ffff80007b1cc018

> > > > > [   38.122249] x21: ffff80007b1cc000 x20: ffff80007b317080

> > > > > [   38.122252] x19: ffff80007a78ce80 x18: 0000000000020000

> > > > > [   38.122255] x17: 0000000000000000 x16: 0000000000000000

> > > > > [   38.122258] x15: 00000000fffffff0 x14: ffff000008c3fb48

> > > > > [   38.122261] x13: ffff000008cdac4a x12: ffff000008c3f000

> > > > > [   38.122264] x11: 0000000000000000 x10: ffff000008cda000

> > > > > [   38.122267] x9 : 0000000000000000 x8 : ffff000008ce4a40

> > > > > [   38.122269] x7 : 0000000000000000 x6 : 0000000039ea41a9

> > > > > [   38.122272] x5 : 0000000000000000 x4 : 0000000000000000

> > > > > [   38.122275] x3 : ffffffffffffffff x2 : c7580c109cae4500

> > > > > [   38.122278] x1 : 0000000000000000 x0 : 0000000000000024

> > > > > [   38.122281] Call trace:

> > > > > [   38.122285]  mdp5_pipe_release+0x90/0xc0

> > > > > [   38.122288]  mdp5_plane_atomic_check+0x2c0/0x448

> > > > > [   38.122294]  drm_atomic_helper_check_planes+0xd0/0x208

> > > > > [   38.122298]  drm_atomic_helper_check+0x38/0xa8

> > > > > [   38.122302]  drm_atomic_check_only+0x3e8/0x630

> > > > > [   38.122305]  drm_atomic_commit+0x18/0x58

> > > > > [   38.122309]  __drm_atomic_helper_disable_all.isra.12+0x15c/0x1a8

> > > > > [   38.122312]  drm_atomic_helper_suspend+0x80/0xf0

> > > > > [   38.122316]  msm_pm_suspend+0x4c/0x70

> > > > > [   38.122320]  dpm_run_callback.isra.6+0x20/0x68

> > > > > [   38.122323]  __device_suspend+0x110/0x308

> > > > > [   38.122326]  dpm_suspend+0x100/0x1f0

> > > > > [   38.122329]  dpm_suspend_start+0x64/0x70

> > > > > [   38.122334]  suspend_devices_and_enter+0x110/0x500

> > > > > [   38.122336]  pm_suspend+0x268/0x2c0

> > > > > [   38.122339]  state_store+0x88/0x110

> > > > > [   38.122345]  kobj_attr_store+0x14/0x28

> > > > > [   38.122352]  sysfs_kf_write+0x3c/0x50

> > > > > [   38.122355]  kernfs_fop_write+0x118/0x1e0

> > > > > [   38.122360]  __vfs_write+0x30/0x168

> > > > > [   38.122363]  vfs_write+0xa4/0x1a8

> > > > > [   38.122366]  ksys_write+0x64/0xe8

> > > > > [   38.122368]  __arm64_sys_write+0x18/0x20

> > > > > [   38.122374]  el0_svc_common+0x6c/0x178

> > > > > [   38.122377]  el0_svc_compat_handler+0x1c/0x28

> > > > > [   38.122381]  el0_svc_compat+0x8/0x18

> > > > > [   38.122383] ---[ end trace 24145b7d8545345b ]---

> > > > > [   38.491552] Disabling non-boot CPUs ...

> > > > >

> > > > > Signed-off-by: Shawn Guo <shawn.guo@linaro.org>

> > > > > ---

> > > > >  drivers/gpu/drm/drm_atomic_helper.c | 16 ++++++++++++++++

> > > > >  1 file changed, 16 insertions(+)

> > > > >

> > > > > diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c

> > > > > index 85d163f16801..024985a92156 100644

> > > > > --- a/drivers/gpu/drm/drm_atomic_helper.c

> > > > > +++ b/drivers/gpu/drm/drm_atomic_helper.c

> > > > > @@ -3140,6 +3140,7 @@ drm_atomic_helper_duplicate_state(struct drm_device *dev,

> > > > >         struct drm_atomic_state *state;

> > > > >         struct drm_connector *conn;

> > > > >         struct drm_connector_list_iter conn_iter;

> > > > > +       struct drm_private_obj *priv_obj;

> > > > >         struct drm_plane *plane;

> > > > >         struct drm_crtc *crtc;

> > > > >         int err = 0;

> > > > > @@ -3184,6 +3185,16 @@ drm_atomic_helper_duplicate_state(struct drm_device *dev,

> > > > >         }

> > > > >         drm_connector_list_iter_end(&conn_iter);

> > > > >

> > > > > +       drm_for_each_privobj(priv_obj, dev) {

> > > > > +               struct drm_private_state *priv_state;

> > > > > +

> > > > > +               priv_state = drm_atomic_get_private_obj_state(state, priv_obj);

> > > > > +               if (IS_ERR(priv_state)) {

> > > > > +                       err = PTR_ERR(priv_state);

> > > > > +                       goto free;

> > > > > +               }

> > > > > +       }

> > > > > +

> > > > >         /* clear the acquire context so that it isn't accidentally reused */

> > > > >         state->acquire_ctx = NULL;

> > > > >

> > > > > @@ -3278,6 +3289,8 @@ int drm_atomic_helper_commit_duplicated_state(struct drm_atomic_state *state,

> > > > >         struct drm_connector_state *new_conn_state;

> > > > >         struct drm_crtc *crtc;

> > > > >         struct drm_crtc_state *new_crtc_state;

> > > > > +       struct drm_private_state *new_priv_state;

> > > > > +       struct drm_private_obj *priv_obj;

> > > > >

> > > > >         state->acquire_ctx = ctx;

> > > > >

> > > > > @@ -3290,6 +3303,9 @@ int drm_atomic_helper_commit_duplicated_state(struct drm_atomic_state *state,

> > > > >         for_each_new_connector_in_state(state, connector, new_conn_state, i)

> > > > >                 state->connectors[i].old_state = connector->state;

> > > > >

> > > > > +       for_each_new_private_obj_in_state(state, priv_obj, new_priv_state, i)

> > > > > +               state->private_objs[i].old_state = priv_obj->state;

> > > > > +

> > > > >         ret = drm_atomic_commit(state);

> > > > >

> > > > >         state->acquire_ctx = NULL;

> > > > > --

> > > > > 2.17.1

> > > > >

> > > >

> > > >

> > > > --

> > > > Daniel Vetter

> > > > Software Engineer, Intel Corporation

> > > > http://blog.ffwll.ch

> >

> >

> >

> > --

> > Daniel Vetter

> > Software Engineer, Intel Corporation

> > http://blog.ffwll.ch


-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
Rob Clark June 26, 2020, 3:25 p.m. | #6
On Fri, Jun 26, 2020 at 6:46 AM Daniel Vetter <daniel@ffwll.ch> wrote:
>

> On Thu, Jun 25, 2020 at 09:24:38AM -0700, Rob Clark wrote:

> > On Thu, Jun 25, 2020 at 8:55 AM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:

> > >

> > > On Thu, Jun 25, 2020 at 4:17 PM Rob Clark <robdclark@gmail.com> wrote:

> > > >

> > > > On Thu, Jun 25, 2020 at 5:35 AM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:

> > > > >

> > > > > On Thu, Jun 25, 2020 at 1:58 PM Shawn Guo <shawnguo@kernel.org> wrote:

> > > > > >

> > > > > > From: Shawn Guo <shawn.guo@linaro.org>

> > > > > >

> > > > > > The msm/mdp5 driver uses drm_private_obj as its global atomic state,

> > > > > > which keeps the assignment of hwpipe to plane.  With drm_private_obj

> > > > > > missing from duplicate state call, mdp5 suspend works with no problem

> > > > > > only for the very first time.  Any subsequent suspend will hit the

> > > > > > following warning, because hwpipe assignment doesn't get duplicated for

> > > > > > suspend state.  Adding drm_private_obj handling for duplicate state call

> > > > > > fixes the problem.

> > > > >

> > > > > If the driver needs a private state, it's supposed to duplicate that

> > > > > in its atomic_check functionality. This isn't the helper's job.

> > > > >

> > > > > If this is a bug in msm code, then pretty sure if you try hard enough,

> > > > > you can hit the exact same bug from userspace too. Maybe good idea to

> > > > > try and reproduce this with igt or something.

> > > >

> > > > The problem is how duplicate_state is used by the atomic

> > > > suspend/resume helpers.  They duplicate the running state on suspend,

> > > > forgetting to duplicate the global state.  Then everything is

> > > > disabled, the driver correctly duplicates and updates it's global

> > > > atomic state releasing the hwpipe.

> > > >

> > > > But then on resume, we are re-applying plane state that thinks it

> > > > already has a hwpipe assigned (because that is part of the plane state

> > > > that was duplicated), without reapplying the matching global state.

> > > >

> > > > On a normal atomic commit, we would duplicate the plane state that has

> > > > the hwpipe disabled, which would be in sync with the drivers global

> > > > state.  But since that is not what the atomic resume helper does, we

> > > > hit the situation where the plane state and the global state are out

> > > > of sync.

> > > >

> > > > So the driver is dtrt, the problem really is with the helpers.  I

> > > > think this patch is the right thing to do.  It is incorrect for the

> > > > suspend/resume helpers to assume that they can re-apply duplicated

> > > > state without including the global state.

> > >

> > > Hm, this is a bit awkward. Generally the assumption is that you should

> > > be recomputing the derived state (like hwpipe) no matter what. If your

> > > driver doesn't do that, then all kinds of things can leak from the

> > > pre-resume to the post-resume side of things, that's kinda why I'm not

> > > thrilled with this patch, I think it has good potential to open up a

> > > can of worms. Iirc this patch has come up in the past, and in those

> > > cases it was a driver bug.

> > >

> > > For this case, why is msm reusing a hw pipe assignment of a disabled plane?

> >

> > Because it is part of the plane state that is being restored.

> >

> > Since resume uses the old state saved before the

> > drm_atomic_helper_disable_all(), rather than duplicating the current

> > state, we end up with this mismatch between global and plane state.  I

> > think stashing away the old state is probably ok, but we can't just do

> > it piecemeal without including the global state.

> >

> > I suppose part of the problem is the hwpipe (and other such

> > dynamically assigned resources) touch both private and plane (and

> > crtc) state.  The global state object knows which resources are

> > assigned to which plane/crtc.  But the plane/crtc state knows which of

> > the (potentially) two hwpipe/mixers is "left" (primary) and "right"

> > (secondary).

>

> Yeah I get all that, what I meant is: Why don't you just blindly recompute

> the hwpipe assignment every time a full modeset is done? Caching it for

> pure plane flips makes sense, but drm_crtc_needs_modset == true and just

> throw it all overboard and assign new ones I think would also solve this

> problem. Since the hwpipe global state would indicate that all pipes are

> unallocated that should work (I hope).

>

> Imo just recomputing state is a good atomic pattern, it avoids drivers

> getting stuck in a corner somewhere you can't reset them out of anymore.

>

> My question here was, why can't you do that?


We do release the hwpipe on disable, and that is where things are
getting out of sync.

I suppose we could do some hack if needs_modeset and walk thru the
global state to detect that we've got ourselves into this condition
and the hwpipe(s) the plane *thinks* it has assigned to itself are no
more.  That sounds like a worse solution.

(note that hwpipe can change for a lot of reasons other than modeset)


>

> > > Unfortunately we can't copy the drm state into the overall structure

> > > to solve this, since that would miss driver-private properties. So

> > > unfortunately we can't make this match a real atomic commit from

> > > userspace perfectly.

> >

> > I'm not sure I understand this?  The driver private properties

> > would/should be part of one of the state objs (plane/crtc/global)?  If

> > the atomic state (including global) represents the entirety of the hw

> > state, you should be able to stash off N different versions of them

> > and re-apply them in any order you want because they are all

> > self-consistent.

>

> So for normal atomic commit we have:

>

> 1. duplicate current state

> 2. set properties

>

> But for resume helpers it's some random older state, so the expectations

> break a bit. We could approximate that using something like:

>

> 1. duplicate current state into curr_state

> 2. set properties using a memcpy of the drm core state structure, leaving

> the driver private stuff as-is.

>

> But a) there's also some non-property state in drm state structures and b)

> properties which are driver extensions and set into the driver part of the

> state would get lost.

>

> So also not great.


Really the solution in this patch sounds like the cleanest solution
(assuming drivers are properly keeping all their state in various
atomic-state objs) ;-)

But replaying all the kms property setting should in theory arrive at
the same state as before the suspend.  But that sounds like the harder
way to do it.

>

> > > Another option would be if msm just copies the private state it needs

> > > to not go boom.

> > >

> > > Doing this unconditionally might break other drivers that rely on

> > > private state not being duplicated, but I guess that would also be

> > > somewhat of a driver bug.

> >

> > I guess we could duplicate our own version of

> > drm_atomic_helper_suspend().. or maybe add a 'duplicate_global' param

> > to drm_atomic_helper_suspend().

> >

> > I'm not too sure how many drivers these days are using global atomic

> > state, so not sure how many would be potentially broken, but opting in

> > to duplicating global state seems reasonable if necessary.

>

> dp mst uses it to track it's stuff at least, and I think it's spreading

> quite a bit into drivers using them to track all kinds of things, not just

> a single global state.


Hmm, if needed we could put a needs_restore flag in the private_state struct?

BR,
-R

> -Daniel

>

> >

> > BR,

> > -R

> >

> > > -Daniel

> > >

> > > >

> > > > BR,

> > > > -R

> > > >

> > > > > -Daniel

> > > > >

> > > > >

> > > > > > $ echo mem > /sys/power/state

> > > > > > [   38.111144] PM: suspend entry (deep)

> > > > > > [   38.111185] PM: Syncing filesystems ... done.

> > > > > > [   38.114630] Freezing user space processes ... (elapsed 0.001 seconds) done.

> > > > > > [   38.115912] OOM killer disabled.

> > > > > > [   38.115914] Freezing remaining freezable tasks ... (elapsed 0.001 seconds) done.

> > > > > > [   38.122170] ------------[ cut here ]------------

> > > > > > [   38.122212] WARNING: CPU: 0 PID: 1747 at drivers/gpu/drm/msm/disp/mdp5/mdp5_pipe.c:145 mdp5_pipe_release+0x90/0xc0

> > > > > > [   38.122215] Modules linked in:

> > > > > > [   38.122222] CPU: 0 PID: 1747 Comm: sh Not tainted 4.19.107-00515-g9d5e4d7a33ed-dirty #323

> > > > > > [   38.122224] Hardware name: Square, Inc. T2 Devkit (DT)

> > > > > > [   38.122228] pstate: 40000005 (nZcv daif -PAN -UAO)

> > > > > > [   38.122230] pc : mdp5_pipe_release+0x90/0xc0

> > > > > > [   38.122233] lr : mdp5_pipe_release+0x90/0xc0

> > > > > > [   38.122235] sp : ffff00000d13b7f0

> > > > > > [   38.122236] x29: ffff00000d13b7f0 x28: 0000000000000000

> > > > > > [   38.122240] x27: 0000000000000002 x26: ffff800079adce00

> > > > > > [   38.122243] x25: ffff800079405200 x24: 0000000000000000

> > > > > > [   38.122246] x23: ffff80007a78cc08 x22: ffff80007b1cc018

> > > > > > [   38.122249] x21: ffff80007b1cc000 x20: ffff80007b317080

> > > > > > [   38.122252] x19: ffff80007a78ce80 x18: 0000000000020000

> > > > > > [   38.122255] x17: 0000000000000000 x16: 0000000000000000

> > > > > > [   38.122258] x15: 00000000fffffff0 x14: ffff000008c3fb48

> > > > > > [   38.122261] x13: ffff000008cdac4a x12: ffff000008c3f000

> > > > > > [   38.122264] x11: 0000000000000000 x10: ffff000008cda000

> > > > > > [   38.122267] x9 : 0000000000000000 x8 : ffff000008ce4a40

> > > > > > [   38.122269] x7 : 0000000000000000 x6 : 0000000039ea41a9

> > > > > > [   38.122272] x5 : 0000000000000000 x4 : 0000000000000000

> > > > > > [   38.122275] x3 : ffffffffffffffff x2 : c7580c109cae4500

> > > > > > [   38.122278] x1 : 0000000000000000 x0 : 0000000000000024

> > > > > > [   38.122281] Call trace:

> > > > > > [   38.122285]  mdp5_pipe_release+0x90/0xc0

> > > > > > [   38.122288]  mdp5_plane_atomic_check+0x2c0/0x448

> > > > > > [   38.122294]  drm_atomic_helper_check_planes+0xd0/0x208

> > > > > > [   38.122298]  drm_atomic_helper_check+0x38/0xa8

> > > > > > [   38.122302]  drm_atomic_check_only+0x3e8/0x630

> > > > > > [   38.122305]  drm_atomic_commit+0x18/0x58

> > > > > > [   38.122309]  __drm_atomic_helper_disable_all.isra.12+0x15c/0x1a8

> > > > > > [   38.122312]  drm_atomic_helper_suspend+0x80/0xf0

> > > > > > [   38.122316]  msm_pm_suspend+0x4c/0x70

> > > > > > [   38.122320]  dpm_run_callback.isra.6+0x20/0x68

> > > > > > [   38.122323]  __device_suspend+0x110/0x308

> > > > > > [   38.122326]  dpm_suspend+0x100/0x1f0

> > > > > > [   38.122329]  dpm_suspend_start+0x64/0x70

> > > > > > [   38.122334]  suspend_devices_and_enter+0x110/0x500

> > > > > > [   38.122336]  pm_suspend+0x268/0x2c0

> > > > > > [   38.122339]  state_store+0x88/0x110

> > > > > > [   38.122345]  kobj_attr_store+0x14/0x28

> > > > > > [   38.122352]  sysfs_kf_write+0x3c/0x50

> > > > > > [   38.122355]  kernfs_fop_write+0x118/0x1e0

> > > > > > [   38.122360]  __vfs_write+0x30/0x168

> > > > > > [   38.122363]  vfs_write+0xa4/0x1a8

> > > > > > [   38.122366]  ksys_write+0x64/0xe8

> > > > > > [   38.122368]  __arm64_sys_write+0x18/0x20

> > > > > > [   38.122374]  el0_svc_common+0x6c/0x178

> > > > > > [   38.122377]  el0_svc_compat_handler+0x1c/0x28

> > > > > > [   38.122381]  el0_svc_compat+0x8/0x18

> > > > > > [   38.122383] ---[ end trace 24145b7d8545345b ]---

> > > > > > [   38.491552] Disabling non-boot CPUs ...

> > > > > >

> > > > > > Signed-off-by: Shawn Guo <shawn.guo@linaro.org>

> > > > > > ---

> > > > > >  drivers/gpu/drm/drm_atomic_helper.c | 16 ++++++++++++++++

> > > > > >  1 file changed, 16 insertions(+)

> > > > > >

> > > > > > diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c

> > > > > > index 85d163f16801..024985a92156 100644

> > > > > > --- a/drivers/gpu/drm/drm_atomic_helper.c

> > > > > > +++ b/drivers/gpu/drm/drm_atomic_helper.c

> > > > > > @@ -3140,6 +3140,7 @@ drm_atomic_helper_duplicate_state(struct drm_device *dev,

> > > > > >         struct drm_atomic_state *state;

> > > > > >         struct drm_connector *conn;

> > > > > >         struct drm_connector_list_iter conn_iter;

> > > > > > +       struct drm_private_obj *priv_obj;

> > > > > >         struct drm_plane *plane;

> > > > > >         struct drm_crtc *crtc;

> > > > > >         int err = 0;

> > > > > > @@ -3184,6 +3185,16 @@ drm_atomic_helper_duplicate_state(struct drm_device *dev,

> > > > > >         }

> > > > > >         drm_connector_list_iter_end(&conn_iter);

> > > > > >

> > > > > > +       drm_for_each_privobj(priv_obj, dev) {

> > > > > > +               struct drm_private_state *priv_state;

> > > > > > +

> > > > > > +               priv_state = drm_atomic_get_private_obj_state(state, priv_obj);

> > > > > > +               if (IS_ERR(priv_state)) {

> > > > > > +                       err = PTR_ERR(priv_state);

> > > > > > +                       goto free;

> > > > > > +               }

> > > > > > +       }

> > > > > > +

> > > > > >         /* clear the acquire context so that it isn't accidentally reused */

> > > > > >         state->acquire_ctx = NULL;

> > > > > >

> > > > > > @@ -3278,6 +3289,8 @@ int drm_atomic_helper_commit_duplicated_state(struct drm_atomic_state *state,

> > > > > >         struct drm_connector_state *new_conn_state;

> > > > > >         struct drm_crtc *crtc;

> > > > > >         struct drm_crtc_state *new_crtc_state;

> > > > > > +       struct drm_private_state *new_priv_state;

> > > > > > +       struct drm_private_obj *priv_obj;

> > > > > >

> > > > > >         state->acquire_ctx = ctx;

> > > > > >

> > > > > > @@ -3290,6 +3303,9 @@ int drm_atomic_helper_commit_duplicated_state(struct drm_atomic_state *state,

> > > > > >         for_each_new_connector_in_state(state, connector, new_conn_state, i)

> > > > > >                 state->connectors[i].old_state = connector->state;

> > > > > >

> > > > > > +       for_each_new_private_obj_in_state(state, priv_obj, new_priv_state, i)

> > > > > > +               state->private_objs[i].old_state = priv_obj->state;

> > > > > > +

> > > > > >         ret = drm_atomic_commit(state);

> > > > > >

> > > > > >         state->acquire_ctx = NULL;

> > > > > > --

> > > > > > 2.17.1

> > > > > >

> > > > >

> > > > >

> > > > > --

> > > > > Daniel Vetter

> > > > > Software Engineer, Intel Corporation

> > > > > http://blog.ffwll.ch

> > >

> > >

> > >

> > > --

> > > Daniel Vetter

> > > Software Engineer, Intel Corporation

> > > http://blog.ffwll.ch

>

> --

> Daniel Vetter

> Software Engineer, Intel Corporation

> http://blog.ffwll.ch
Daniel Vetter June 26, 2020, 9:21 p.m. | #7
On Fri, Jun 26, 2020 at 08:25:18AM -0700, Rob Clark wrote:
> On Fri, Jun 26, 2020 at 6:46 AM Daniel Vetter <daniel@ffwll.ch> wrote:

> >

> > On Thu, Jun 25, 2020 at 09:24:38AM -0700, Rob Clark wrote:

> > > On Thu, Jun 25, 2020 at 8:55 AM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:

> > > >

> > > > On Thu, Jun 25, 2020 at 4:17 PM Rob Clark <robdclark@gmail.com> wrote:

> > > > >

> > > > > On Thu, Jun 25, 2020 at 5:35 AM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:

> > > > > >

> > > > > > On Thu, Jun 25, 2020 at 1:58 PM Shawn Guo <shawnguo@kernel.org> wrote:

> > > > > > >

> > > > > > > From: Shawn Guo <shawn.guo@linaro.org>

> > > > > > >

> > > > > > > The msm/mdp5 driver uses drm_private_obj as its global atomic state,

> > > > > > > which keeps the assignment of hwpipe to plane.  With drm_private_obj

> > > > > > > missing from duplicate state call, mdp5 suspend works with no problem

> > > > > > > only for the very first time.  Any subsequent suspend will hit the

> > > > > > > following warning, because hwpipe assignment doesn't get duplicated for

> > > > > > > suspend state.  Adding drm_private_obj handling for duplicate state call

> > > > > > > fixes the problem.

> > > > > >

> > > > > > If the driver needs a private state, it's supposed to duplicate that

> > > > > > in its atomic_check functionality. This isn't the helper's job.

> > > > > >

> > > > > > If this is a bug in msm code, then pretty sure if you try hard enough,

> > > > > > you can hit the exact same bug from userspace too. Maybe good idea to

> > > > > > try and reproduce this with igt or something.

> > > > >

> > > > > The problem is how duplicate_state is used by the atomic

> > > > > suspend/resume helpers.  They duplicate the running state on suspend,

> > > > > forgetting to duplicate the global state.  Then everything is

> > > > > disabled, the driver correctly duplicates and updates it's global

> > > > > atomic state releasing the hwpipe.

> > > > >

> > > > > But then on resume, we are re-applying plane state that thinks it

> > > > > already has a hwpipe assigned (because that is part of the plane state

> > > > > that was duplicated), without reapplying the matching global state.

> > > > >

> > > > > On a normal atomic commit, we would duplicate the plane state that has

> > > > > the hwpipe disabled, which would be in sync with the drivers global

> > > > > state.  But since that is not what the atomic resume helper does, we

> > > > > hit the situation where the plane state and the global state are out

> > > > > of sync.

> > > > >

> > > > > So the driver is dtrt, the problem really is with the helpers.  I

> > > > > think this patch is the right thing to do.  It is incorrect for the

> > > > > suspend/resume helpers to assume that they can re-apply duplicated

> > > > > state without including the global state.

> > > >

> > > > Hm, this is a bit awkward. Generally the assumption is that you should

> > > > be recomputing the derived state (like hwpipe) no matter what. If your

> > > > driver doesn't do that, then all kinds of things can leak from the

> > > > pre-resume to the post-resume side of things, that's kinda why I'm not

> > > > thrilled with this patch, I think it has good potential to open up a

> > > > can of worms. Iirc this patch has come up in the past, and in those

> > > > cases it was a driver bug.

> > > >

> > > > For this case, why is msm reusing a hw pipe assignment of a disabled plane?

> > >

> > > Because it is part of the plane state that is being restored.

> > >

> > > Since resume uses the old state saved before the

> > > drm_atomic_helper_disable_all(), rather than duplicating the current

> > > state, we end up with this mismatch between global and plane state.  I

> > > think stashing away the old state is probably ok, but we can't just do

> > > it piecemeal without including the global state.

> > >

> > > I suppose part of the problem is the hwpipe (and other such

> > > dynamically assigned resources) touch both private and plane (and

> > > crtc) state.  The global state object knows which resources are

> > > assigned to which plane/crtc.  But the plane/crtc state knows which of

> > > the (potentially) two hwpipe/mixers is "left" (primary) and "right"

> > > (secondary).

> >

> > Yeah I get all that, what I meant is: Why don't you just blindly recompute

> > the hwpipe assignment every time a full modeset is done? Caching it for

> > pure plane flips makes sense, but drm_crtc_needs_modset == true and just

> > throw it all overboard and assign new ones I think would also solve this

> > problem. Since the hwpipe global state would indicate that all pipes are

> > unallocated that should work (I hope).

> >

> > Imo just recomputing state is a good atomic pattern, it avoids drivers

> > getting stuck in a corner somewhere you can't reset them out of anymore.

> >

> > My question here was, why can't you do that?

> 

> We do release the hwpipe on disable, and that is where things are

> getting out of sync.

> 

> I suppose we could do some hack if needs_modeset and walk thru the

> global state to detect that we've got ourselves into this condition

> and the hwpipe(s) the plane *thinks* it has assigned to itself are no

> more.  That sounds like a worse solution.

> 

> (note that hwpipe can change for a lot of reasons other than modeset)

> 

> 

> >

> > > > Unfortunately we can't copy the drm state into the overall structure

> > > > to solve this, since that would miss driver-private properties. So

> > > > unfortunately we can't make this match a real atomic commit from

> > > > userspace perfectly.

> > >

> > > I'm not sure I understand this?  The driver private properties

> > > would/should be part of one of the state objs (plane/crtc/global)?  If

> > > the atomic state (including global) represents the entirety of the hw

> > > state, you should be able to stash off N different versions of them

> > > and re-apply them in any order you want because they are all

> > > self-consistent.

> >

> > So for normal atomic commit we have:

> >

> > 1. duplicate current state

> > 2. set properties

> >

> > But for resume helpers it's some random older state, so the expectations

> > break a bit. We could approximate that using something like:

> >

> > 1. duplicate current state into curr_state

> > 2. set properties using a memcpy of the drm core state structure, leaving

> > the driver private stuff as-is.

> >

> > But a) there's also some non-property state in drm state structures and b)

> > properties which are driver extensions and set into the driver part of the

> > state would get lost.

> >

> > So also not great.

> 

> Really the solution in this patch sounds like the cleanest solution

> (assuming drivers are properly keeping all their state in various

> atomic-state objs) ;-)

> 

> But replaying all the kms property setting should in theory arrive at

> the same state as before the suspend.  But that sounds like the harder

> way to do it.

> 

> >

> > > > Another option would be if msm just copies the private state it needs

> > > > to not go boom.

> > > >

> > > > Doing this unconditionally might break other drivers that rely on

> > > > private state not being duplicated, but I guess that would also be

> > > > somewhat of a driver bug.

> > >

> > > I guess we could duplicate our own version of

> > > drm_atomic_helper_suspend().. or maybe add a 'duplicate_global' param

> > > to drm_atomic_helper_suspend().

> > >

> > > I'm not too sure how many drivers these days are using global atomic

> > > state, so not sure how many would be potentially broken, but opting in

> > > to duplicating global state seems reasonable if necessary.

> >

> > dp mst uses it to track it's stuff at least, and I think it's spreading

> > quite a bit into drivers using them to track all kinds of things, not just

> > a single global state.

> 

> Hmm, if needed we could put a needs_restore flag in the private_state struct?


drm_private_obj, not the state, since this should be invariant. And I
think this is the cleanest solution of them all. Also gives us a nice
place for some kerneldoc with links to suspend/resume helpers and why you
might need this.
-Daniel

> 

> BR,

> -R

> 

> > -Daniel

> >

> > >

> > > BR,

> > > -R

> > >

> > > > -Daniel

> > > >

> > > > >

> > > > > BR,

> > > > > -R

> > > > >

> > > > > > -Daniel

> > > > > >

> > > > > >

> > > > > > > $ echo mem > /sys/power/state

> > > > > > > [   38.111144] PM: suspend entry (deep)

> > > > > > > [   38.111185] PM: Syncing filesystems ... done.

> > > > > > > [   38.114630] Freezing user space processes ... (elapsed 0.001 seconds) done.

> > > > > > > [   38.115912] OOM killer disabled.

> > > > > > > [   38.115914] Freezing remaining freezable tasks ... (elapsed 0.001 seconds) done.

> > > > > > > [   38.122170] ------------[ cut here ]------------

> > > > > > > [   38.122212] WARNING: CPU: 0 PID: 1747 at drivers/gpu/drm/msm/disp/mdp5/mdp5_pipe.c:145 mdp5_pipe_release+0x90/0xc0

> > > > > > > [   38.122215] Modules linked in:

> > > > > > > [   38.122222] CPU: 0 PID: 1747 Comm: sh Not tainted 4.19.107-00515-g9d5e4d7a33ed-dirty #323

> > > > > > > [   38.122224] Hardware name: Square, Inc. T2 Devkit (DT)

> > > > > > > [   38.122228] pstate: 40000005 (nZcv daif -PAN -UAO)

> > > > > > > [   38.122230] pc : mdp5_pipe_release+0x90/0xc0

> > > > > > > [   38.122233] lr : mdp5_pipe_release+0x90/0xc0

> > > > > > > [   38.122235] sp : ffff00000d13b7f0

> > > > > > > [   38.122236] x29: ffff00000d13b7f0 x28: 0000000000000000

> > > > > > > [   38.122240] x27: 0000000000000002 x26: ffff800079adce00

> > > > > > > [   38.122243] x25: ffff800079405200 x24: 0000000000000000

> > > > > > > [   38.122246] x23: ffff80007a78cc08 x22: ffff80007b1cc018

> > > > > > > [   38.122249] x21: ffff80007b1cc000 x20: ffff80007b317080

> > > > > > > [   38.122252] x19: ffff80007a78ce80 x18: 0000000000020000

> > > > > > > [   38.122255] x17: 0000000000000000 x16: 0000000000000000

> > > > > > > [   38.122258] x15: 00000000fffffff0 x14: ffff000008c3fb48

> > > > > > > [   38.122261] x13: ffff000008cdac4a x12: ffff000008c3f000

> > > > > > > [   38.122264] x11: 0000000000000000 x10: ffff000008cda000

> > > > > > > [   38.122267] x9 : 0000000000000000 x8 : ffff000008ce4a40

> > > > > > > [   38.122269] x7 : 0000000000000000 x6 : 0000000039ea41a9

> > > > > > > [   38.122272] x5 : 0000000000000000 x4 : 0000000000000000

> > > > > > > [   38.122275] x3 : ffffffffffffffff x2 : c7580c109cae4500

> > > > > > > [   38.122278] x1 : 0000000000000000 x0 : 0000000000000024

> > > > > > > [   38.122281] Call trace:

> > > > > > > [   38.122285]  mdp5_pipe_release+0x90/0xc0

> > > > > > > [   38.122288]  mdp5_plane_atomic_check+0x2c0/0x448

> > > > > > > [   38.122294]  drm_atomic_helper_check_planes+0xd0/0x208

> > > > > > > [   38.122298]  drm_atomic_helper_check+0x38/0xa8

> > > > > > > [   38.122302]  drm_atomic_check_only+0x3e8/0x630

> > > > > > > [   38.122305]  drm_atomic_commit+0x18/0x58

> > > > > > > [   38.122309]  __drm_atomic_helper_disable_all.isra.12+0x15c/0x1a8

> > > > > > > [   38.122312]  drm_atomic_helper_suspend+0x80/0xf0

> > > > > > > [   38.122316]  msm_pm_suspend+0x4c/0x70

> > > > > > > [   38.122320]  dpm_run_callback.isra.6+0x20/0x68

> > > > > > > [   38.122323]  __device_suspend+0x110/0x308

> > > > > > > [   38.122326]  dpm_suspend+0x100/0x1f0

> > > > > > > [   38.122329]  dpm_suspend_start+0x64/0x70

> > > > > > > [   38.122334]  suspend_devices_and_enter+0x110/0x500

> > > > > > > [   38.122336]  pm_suspend+0x268/0x2c0

> > > > > > > [   38.122339]  state_store+0x88/0x110

> > > > > > > [   38.122345]  kobj_attr_store+0x14/0x28

> > > > > > > [   38.122352]  sysfs_kf_write+0x3c/0x50

> > > > > > > [   38.122355]  kernfs_fop_write+0x118/0x1e0

> > > > > > > [   38.122360]  __vfs_write+0x30/0x168

> > > > > > > [   38.122363]  vfs_write+0xa4/0x1a8

> > > > > > > [   38.122366]  ksys_write+0x64/0xe8

> > > > > > > [   38.122368]  __arm64_sys_write+0x18/0x20

> > > > > > > [   38.122374]  el0_svc_common+0x6c/0x178

> > > > > > > [   38.122377]  el0_svc_compat_handler+0x1c/0x28

> > > > > > > [   38.122381]  el0_svc_compat+0x8/0x18

> > > > > > > [   38.122383] ---[ end trace 24145b7d8545345b ]---

> > > > > > > [   38.491552] Disabling non-boot CPUs ...

> > > > > > >

> > > > > > > Signed-off-by: Shawn Guo <shawn.guo@linaro.org>

> > > > > > > ---

> > > > > > >  drivers/gpu/drm/drm_atomic_helper.c | 16 ++++++++++++++++

> > > > > > >  1 file changed, 16 insertions(+)

> > > > > > >

> > > > > > > diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c

> > > > > > > index 85d163f16801..024985a92156 100644

> > > > > > > --- a/drivers/gpu/drm/drm_atomic_helper.c

> > > > > > > +++ b/drivers/gpu/drm/drm_atomic_helper.c

> > > > > > > @@ -3140,6 +3140,7 @@ drm_atomic_helper_duplicate_state(struct drm_device *dev,

> > > > > > >         struct drm_atomic_state *state;

> > > > > > >         struct drm_connector *conn;

> > > > > > >         struct drm_connector_list_iter conn_iter;

> > > > > > > +       struct drm_private_obj *priv_obj;

> > > > > > >         struct drm_plane *plane;

> > > > > > >         struct drm_crtc *crtc;

> > > > > > >         int err = 0;

> > > > > > > @@ -3184,6 +3185,16 @@ drm_atomic_helper_duplicate_state(struct drm_device *dev,

> > > > > > >         }

> > > > > > >         drm_connector_list_iter_end(&conn_iter);

> > > > > > >

> > > > > > > +       drm_for_each_privobj(priv_obj, dev) {

> > > > > > > +               struct drm_private_state *priv_state;

> > > > > > > +

> > > > > > > +               priv_state = drm_atomic_get_private_obj_state(state, priv_obj);

> > > > > > > +               if (IS_ERR(priv_state)) {

> > > > > > > +                       err = PTR_ERR(priv_state);

> > > > > > > +                       goto free;

> > > > > > > +               }

> > > > > > > +       }

> > > > > > > +

> > > > > > >         /* clear the acquire context so that it isn't accidentally reused */

> > > > > > >         state->acquire_ctx = NULL;

> > > > > > >

> > > > > > > @@ -3278,6 +3289,8 @@ int drm_atomic_helper_commit_duplicated_state(struct drm_atomic_state *state,

> > > > > > >         struct drm_connector_state *new_conn_state;

> > > > > > >         struct drm_crtc *crtc;

> > > > > > >         struct drm_crtc_state *new_crtc_state;

> > > > > > > +       struct drm_private_state *new_priv_state;

> > > > > > > +       struct drm_private_obj *priv_obj;

> > > > > > >

> > > > > > >         state->acquire_ctx = ctx;

> > > > > > >

> > > > > > > @@ -3290,6 +3303,9 @@ int drm_atomic_helper_commit_duplicated_state(struct drm_atomic_state *state,

> > > > > > >         for_each_new_connector_in_state(state, connector, new_conn_state, i)

> > > > > > >                 state->connectors[i].old_state = connector->state;

> > > > > > >

> > > > > > > +       for_each_new_private_obj_in_state(state, priv_obj, new_priv_state, i)

> > > > > > > +               state->private_objs[i].old_state = priv_obj->state;

> > > > > > > +

> > > > > > >         ret = drm_atomic_commit(state);

> > > > > > >

> > > > > > >         state->acquire_ctx = NULL;

> > > > > > > --

> > > > > > > 2.17.1

> > > > > > >

> > > > > >

> > > > > >

> > > > > > --

> > > > > > Daniel Vetter

> > > > > > Software Engineer, Intel Corporation

> > > > > > http://blog.ffwll.ch

> > > >

> > > >

> > > >

> > > > --

> > > > Daniel Vetter

> > > > Software Engineer, Intel Corporation

> > > > http://blog.ffwll.ch

> >

> > --

> > Daniel Vetter

> > Software Engineer, Intel Corporation

> > http://blog.ffwll.ch


-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

Patch

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index 85d163f16801..024985a92156 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -3140,6 +3140,7 @@  drm_atomic_helper_duplicate_state(struct drm_device *dev,
 	struct drm_atomic_state *state;
 	struct drm_connector *conn;
 	struct drm_connector_list_iter conn_iter;
+	struct drm_private_obj *priv_obj;
 	struct drm_plane *plane;
 	struct drm_crtc *crtc;
 	int err = 0;
@@ -3184,6 +3185,16 @@  drm_atomic_helper_duplicate_state(struct drm_device *dev,
 	}
 	drm_connector_list_iter_end(&conn_iter);
 
+	drm_for_each_privobj(priv_obj, dev) {
+		struct drm_private_state *priv_state;
+
+		priv_state = drm_atomic_get_private_obj_state(state, priv_obj);
+		if (IS_ERR(priv_state)) {
+			err = PTR_ERR(priv_state);
+			goto free;
+		}
+	}
+
 	/* clear the acquire context so that it isn't accidentally reused */
 	state->acquire_ctx = NULL;
 
@@ -3278,6 +3289,8 @@  int drm_atomic_helper_commit_duplicated_state(struct drm_atomic_state *state,
 	struct drm_connector_state *new_conn_state;
 	struct drm_crtc *crtc;
 	struct drm_crtc_state *new_crtc_state;
+	struct drm_private_state *new_priv_state;
+	struct drm_private_obj *priv_obj;
 
 	state->acquire_ctx = ctx;
 
@@ -3290,6 +3303,9 @@  int drm_atomic_helper_commit_duplicated_state(struct drm_atomic_state *state,
 	for_each_new_connector_in_state(state, connector, new_conn_state, i)
 		state->connectors[i].old_state = connector->state;
 
+	for_each_new_private_obj_in_state(state, priv_obj, new_priv_state, i)
+		state->private_objs[i].old_state = priv_obj->state;
+
 	ret = drm_atomic_commit(state);
 
 	state->acquire_ctx = NULL;