| Message ID | 20190124120658.30288-1-ard.biesheuvel@linaro.org |
|---|---|
| State | Accepted |
| Commit | e02f5c1bb2283cfcee68f2f0feddcc06150f13aa |
| Headers | show |
| Series | drm: enable uncached DMA optimization for ARM and arm64 | expand |
Am 24.01.19 um 13:06 schrieb Ard Biesheuvel: > The DRM driver stack is designed to work with cache coherent devices > only, but permits an optimization to be enabled in some cases, where > for some buffers, both the CPU and the GPU use uncached mappings, > removing the need for DMA snooping and allocation in the CPU caches. > > The use of uncached GPU mappings relies on the correct implementation > of the PCIe NoSnoop TLP attribute by the platform, otherwise the GPU > will use cached mappings nonetheless. On x86 platforms, this does not > seem to matter, as uncached CPU mappings will snoop the caches in any > case. However, on ARM and arm64, enabling this optimization on a > platform where NoSnoop is ignored results in loss of coherency, which > breaks correct operation of the device. Since we have no way of > detecting whether NoSnoop works or not, just disable this > optimization entirely for ARM and arm64. > > Cc: Christian Koenig <christian.koenig@amd.com> > Cc: Alex Deucher <alexander.deucher@amd.com> > Cc: David Zhou <David1.Zhou@amd.com> > Cc: Huang Rui <ray.huang@amd.com> > Cc: Junwei Zhang <Jerry.Zhang@amd.com> > Cc: Michel Daenzer <michel.daenzer@amd.com> > Cc: David Airlie <airlied@linux.ie> > Cc: Daniel Vetter <daniel@ffwll.ch> > Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> > Cc: Maxime Ripard <maxime.ripard@bootlin.com> > Cc: Sean Paul <sean@poorly.run> > Cc: Michael Ellerman <mpe@ellerman.id.au> > Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> > Cc: Will Deacon <will.deacon@arm.com> > Cc: Christoph Hellwig <hch@infradead.org> > Cc: Robin Murphy <robin.murphy@arm.com> > Cc: amd-gfx list <amd-gfx@lists.freedesktop.org> > Cc: dri-devel <dri-devel@lists.freedesktop.org> > Reported-by: Carsten Haitzler <Carsten.Haitzler@arm.com> > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> The subject line should probably read "disable uncached...". With that fixed the patch is Reviewed-by: Christian König <christian.koenig@amd.com>. Regards, Christian. > --- > include/drm/drm_cache.h | 18 ++++++++++++++++++ > 1 file changed, 18 insertions(+) > > diff --git a/include/drm/drm_cache.h b/include/drm/drm_cache.h > index bfe1639df02d..97fc498dc767 100644 > --- a/include/drm/drm_cache.h > +++ b/include/drm/drm_cache.h > @@ -47,6 +47,24 @@ static inline bool drm_arch_can_wc_memory(void) > return false; > #elif defined(CONFIG_MIPS) && defined(CONFIG_CPU_LOONGSON3) > return false; > +#elif defined(CONFIG_ARM) || defined(CONFIG_ARM64) > + /* > + * The DRM driver stack is designed to work with cache coherent devices > + * only, but permits an optimization to be enabled in some cases, where > + * for some buffers, both the CPU and the GPU use uncached mappings, > + * removing the need for DMA snooping and allocation in the CPU caches. > + * > + * The use of uncached GPU mappings relies on the correct implementation > + * of the PCIe NoSnoop TLP attribute by the platform, otherwise the GPU > + * will use cached mappings nonetheless. On x86 platforms, this does not > + * seem to matter, as uncached CPU mappings will snoop the caches in any > + * case. However, on ARM and arm64, enabling this optimization on a > + * platform where NoSnoop is ignored results in loss of coherency, which > + * breaks correct operation of the device. Since we have no way of > + * detecting whether NoSnoop works or not, just disable this > + * optimization entirely for ARM and arm64. > + */ > + return false; > #else > return true; > #endif
On Thu, 24 Jan 2019 at 13:31, Koenig, Christian <Christian.Koenig@amd.com> wrote: > > Am 24.01.19 um 13:06 schrieb Ard Biesheuvel: > > The DRM driver stack is designed to work with cache coherent devices > > only, but permits an optimization to be enabled in some cases, where > > for some buffers, both the CPU and the GPU use uncached mappings, > > removing the need for DMA snooping and allocation in the CPU caches. > > > > The use of uncached GPU mappings relies on the correct implementation > > of the PCIe NoSnoop TLP attribute by the platform, otherwise the GPU > > will use cached mappings nonetheless. On x86 platforms, this does not > > seem to matter, as uncached CPU mappings will snoop the caches in any > > case. However, on ARM and arm64, enabling this optimization on a > > platform where NoSnoop is ignored results in loss of coherency, which > > breaks correct operation of the device. Since we have no way of > > detecting whether NoSnoop works or not, just disable this > > optimization entirely for ARM and arm64. > > > > Cc: Christian Koenig <christian.koenig@amd.com> > > Cc: Alex Deucher <alexander.deucher@amd.com> > > Cc: David Zhou <David1.Zhou@amd.com> > > Cc: Huang Rui <ray.huang@amd.com> > > Cc: Junwei Zhang <Jerry.Zhang@amd.com> > > Cc: Michel Daenzer <michel.daenzer@amd.com> > > Cc: David Airlie <airlied@linux.ie> > > Cc: Daniel Vetter <daniel@ffwll.ch> > > Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> > > Cc: Maxime Ripard <maxime.ripard@bootlin.com> > > Cc: Sean Paul <sean@poorly.run> > > Cc: Michael Ellerman <mpe@ellerman.id.au> > > Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> > > Cc: Will Deacon <will.deacon@arm.com> > > Cc: Christoph Hellwig <hch@infradead.org> > > Cc: Robin Murphy <robin.murphy@arm.com> > > Cc: amd-gfx list <amd-gfx@lists.freedesktop.org> > > Cc: dri-devel <dri-devel@lists.freedesktop.org> > > Reported-by: Carsten Haitzler <Carsten.Haitzler@arm.com> > > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> > > The subject line should probably read "disable uncached...". > Ugh, of course ... > With that fixed the patch is Reviewed-by: Christian König > <christian.koenig@amd.com>. > Thanks.
On Thu, 24 Jan 2019 at 15:01, Alex Deucher <alexdeucher@gmail.com> wrote: > > On Thu, Jan 24, 2019 at 9:00 AM Ard Biesheuvel > <ard.biesheuvel@linaro.org> wrote: > > > > On Thu, 24 Jan 2019 at 13:31, Koenig, Christian > > <Christian.Koenig@amd.com> wrote: > > > > > > Am 24.01.19 um 13:06 schrieb Ard Biesheuvel: > > > > The DRM driver stack is designed to work with cache coherent devices > > > > only, but permits an optimization to be enabled in some cases, where > > > > for some buffers, both the CPU and the GPU use uncached mappings, > > > > removing the need for DMA snooping and allocation in the CPU caches. > > > > > > > > The use of uncached GPU mappings relies on the correct implementation > > > > of the PCIe NoSnoop TLP attribute by the platform, otherwise the GPU > > > > will use cached mappings nonetheless. On x86 platforms, this does not > > > > seem to matter, as uncached CPU mappings will snoop the caches in any > > > > case. However, on ARM and arm64, enabling this optimization on a > > > > platform where NoSnoop is ignored results in loss of coherency, which > > > > breaks correct operation of the device. Since we have no way of > > > > detecting whether NoSnoop works or not, just disable this > > > > optimization entirely for ARM and arm64. > > > > > > > > Cc: Christian Koenig <christian.koenig@amd.com> > > > > Cc: Alex Deucher <alexander.deucher@amd.com> > > > > Cc: David Zhou <David1.Zhou@amd.com> > > > > Cc: Huang Rui <ray.huang@amd.com> > > > > Cc: Junwei Zhang <Jerry.Zhang@amd.com> > > > > Cc: Michel Daenzer <michel.daenzer@amd.com> > > > > Cc: David Airlie <airlied@linux.ie> > > > > Cc: Daniel Vetter <daniel@ffwll.ch> > > > > Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> > > > > Cc: Maxime Ripard <maxime.ripard@bootlin.com> > > > > Cc: Sean Paul <sean@poorly.run> > > > > Cc: Michael Ellerman <mpe@ellerman.id.au> > > > > Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> > > > > Cc: Will Deacon <will.deacon@arm.com> > > > > Cc: Christoph Hellwig <hch@infradead.org> > > > > Cc: Robin Murphy <robin.murphy@arm.com> > > > > Cc: amd-gfx list <amd-gfx@lists.freedesktop.org> > > > > Cc: dri-devel <dri-devel@lists.freedesktop.org> > > > > Reported-by: Carsten Haitzler <Carsten.Haitzler@arm.com> > > > > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> > > > > > > The subject line should probably read "disable uncached...". > > > > > > > Ugh, of course ... > > > > > With that fixed the patch is Reviewed-by: Christian König > > > <christian.koenig@amd.com>. > > > > > Same: > Reviewed-by: Alex Deucher <alexander.deucher@amd.com> > Thanks all Should I resend the patch with the subject corrected?
On Fri, 25 Jan 2019 at 12:30, Christian König <ckoenig.leichtzumerken@gmail.com> wrote: > > Am 25.01.19 um 09:43 schrieb Ard Biesheuvel: > > On Thu, 24 Jan 2019 at 15:01, Alex Deucher <alexdeucher@gmail.com> wrote: > >> On Thu, Jan 24, 2019 at 9:00 AM Ard Biesheuvel > >> <ard.biesheuvel@linaro.org> wrote: > >>> On Thu, 24 Jan 2019 at 13:31, Koenig, Christian > >>> <Christian.Koenig@amd.com> wrote: > >>>> Am 24.01.19 um 13:06 schrieb Ard Biesheuvel: > >>>>> The DRM driver stack is designed to work with cache coherent devices > >>>>> only, but permits an optimization to be enabled in some cases, where > >>>>> for some buffers, both the CPU and the GPU use uncached mappings, > >>>>> removing the need for DMA snooping and allocation in the CPU caches. > >>>>> > >>>>> The use of uncached GPU mappings relies on the correct implementation > >>>>> of the PCIe NoSnoop TLP attribute by the platform, otherwise the GPU > >>>>> will use cached mappings nonetheless. On x86 platforms, this does not > >>>>> seem to matter, as uncached CPU mappings will snoop the caches in any > >>>>> case. However, on ARM and arm64, enabling this optimization on a > >>>>> platform where NoSnoop is ignored results in loss of coherency, which > >>>>> breaks correct operation of the device. Since we have no way of > >>>>> detecting whether NoSnoop works or not, just disable this > >>>>> optimization entirely for ARM and arm64. > >>>>> > >>>>> Cc: Christian Koenig <christian.koenig@amd.com> > >>>>> Cc: Alex Deucher <alexander.deucher@amd.com> > >>>>> Cc: David Zhou <David1.Zhou@amd.com> > >>>>> Cc: Huang Rui <ray.huang@amd.com> > >>>>> Cc: Junwei Zhang <Jerry.Zhang@amd.com> > >>>>> Cc: Michel Daenzer <michel.daenzer@amd.com> > >>>>> Cc: David Airlie <airlied@linux.ie> > >>>>> Cc: Daniel Vetter <daniel@ffwll.ch> > >>>>> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> > >>>>> Cc: Maxime Ripard <maxime.ripard@bootlin.com> > >>>>> Cc: Sean Paul <sean@poorly.run> > >>>>> Cc: Michael Ellerman <mpe@ellerman.id.au> > >>>>> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> > >>>>> Cc: Will Deacon <will.deacon@arm.com> > >>>>> Cc: Christoph Hellwig <hch@infradead.org> > >>>>> Cc: Robin Murphy <robin.murphy@arm.com> > >>>>> Cc: amd-gfx list <amd-gfx@lists.freedesktop.org> > >>>>> Cc: dri-devel <dri-devel@lists.freedesktop.org> > >>>>> Reported-by: Carsten Haitzler <Carsten.Haitzler@arm.com> > >>>>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> > >>>> The subject line should probably read "disable uncached...". > >>>> > >>> Ugh, of course ... > >>> > >>>> With that fixed the patch is Reviewed-by: Christian König > >>>> <christian.koenig@amd.com>. > >>>> > >> Same: > >> Reviewed-by: Alex Deucher <alexander.deucher@amd.com> > >> > > Thanks all > > > > Should I resend the patch with the subject corrected? > > I will update the subject line and push it upstream through > drm-misc-next if nobody objects. > Wonderful, thanks.
On Fri, 25 Jan 2019 at 11:35, Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote: > > On Fri, 25 Jan 2019 at 12:30, Christian König > <ckoenig.leichtzumerken@gmail.com> wrote: > > > > Am 25.01.19 um 09:43 schrieb Ard Biesheuvel: > > > On Thu, 24 Jan 2019 at 15:01, Alex Deucher <alexdeucher@gmail.com> wrote: > > >> On Thu, Jan 24, 2019 at 9:00 AM Ard Biesheuvel > > >> <ard.biesheuvel@linaro.org> wrote: > > >>> On Thu, 24 Jan 2019 at 13:31, Koenig, Christian > > >>> <Christian.Koenig@amd.com> wrote: > > >>>> Am 24.01.19 um 13:06 schrieb Ard Biesheuvel: > > >>>>> The DRM driver stack is designed to work with cache coherent devices > > >>>>> only, but permits an optimization to be enabled in some cases, where > > >>>>> for some buffers, both the CPU and the GPU use uncached mappings, > > >>>>> removing the need for DMA snooping and allocation in the CPU caches. > > >>>>> > > >>>>> The use of uncached GPU mappings relies on the correct implementation > > >>>>> of the PCIe NoSnoop TLP attribute by the platform, otherwise the GPU > > >>>>> will use cached mappings nonetheless. On x86 platforms, this does not > > >>>>> seem to matter, as uncached CPU mappings will snoop the caches in any > > >>>>> case. However, on ARM and arm64, enabling this optimization on a > > >>>>> platform where NoSnoop is ignored results in loss of coherency, which > > >>>>> breaks correct operation of the device. Since we have no way of > > >>>>> detecting whether NoSnoop works or not, just disable this > > >>>>> optimization entirely for ARM and arm64. > > >>>>> > > >>>>> Cc: Christian Koenig <christian.koenig@amd.com> > > >>>>> Cc: Alex Deucher <alexander.deucher@amd.com> > > >>>>> Cc: David Zhou <David1.Zhou@amd.com> > > >>>>> Cc: Huang Rui <ray.huang@amd.com> > > >>>>> Cc: Junwei Zhang <Jerry.Zhang@amd.com> > > >>>>> Cc: Michel Daenzer <michel.daenzer@amd.com> > > >>>>> Cc: David Airlie <airlied@linux.ie> > > >>>>> Cc: Daniel Vetter <daniel@ffwll.ch> > > >>>>> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> > > >>>>> Cc: Maxime Ripard <maxime.ripard@bootlin.com> > > >>>>> Cc: Sean Paul <sean@poorly.run> > > >>>>> Cc: Michael Ellerman <mpe@ellerman.id.au> > > >>>>> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> > > >>>>> Cc: Will Deacon <will.deacon@arm.com> > > >>>>> Cc: Christoph Hellwig <hch@infradead.org> > > >>>>> Cc: Robin Murphy <robin.murphy@arm.com> > > >>>>> Cc: amd-gfx list <amd-gfx@lists.freedesktop.org> > > >>>>> Cc: dri-devel <dri-devel@lists.freedesktop.org> > > >>>>> Reported-by: Carsten Haitzler <Carsten.Haitzler@arm.com> > > >>>>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> > > >>>> The subject line should probably read "disable uncached...". > > >>>> > > >>> Ugh, of course ... > > >>> > > >>>> With that fixed the patch is Reviewed-by: Christian König > > >>>> <christian.koenig@amd.com>. > > >>>> > > >> Same: > > >> Reviewed-by: Alex Deucher <alexander.deucher@amd.com> > > >> > > > Thanks all > > > > > > Should I resend the patch with the subject corrected? > > > > I will update the subject line and push it upstream through > > drm-misc-next if nobody objects. > > > > Wonderful, thanks. Hi Christian, Are you still planning to merge this for v5.1? Thanks, Ard.
Am 06.02.19 um 18:23 schrieb Ard Biesheuvel: > On Fri, 25 Jan 2019 at 11:35, Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote: >> On Fri, 25 Jan 2019 at 12:30, Christian König >> <ckoenig.leichtzumerken@gmail.com> wrote: >>> Am 25.01.19 um 09:43 schrieb Ard Biesheuvel: >>>> On Thu, 24 Jan 2019 at 15:01, Alex Deucher <alexdeucher@gmail.com> wrote: >>>>> On Thu, Jan 24, 2019 at 9:00 AM Ard Biesheuvel >>>>> <ard.biesheuvel@linaro.org> wrote: >>>>>> On Thu, 24 Jan 2019 at 13:31, Koenig, Christian >>>>>> <Christian.Koenig@amd.com> wrote: >>>>>>> Am 24.01.19 um 13:06 schrieb Ard Biesheuvel: >>>>>>>> The DRM driver stack is designed to work with cache coherent devices >>>>>>>> only, but permits an optimization to be enabled in some cases, where >>>>>>>> for some buffers, both the CPU and the GPU use uncached mappings, >>>>>>>> removing the need for DMA snooping and allocation in the CPU caches. >>>>>>>> >>>>>>>> The use of uncached GPU mappings relies on the correct implementation >>>>>>>> of the PCIe NoSnoop TLP attribute by the platform, otherwise the GPU >>>>>>>> will use cached mappings nonetheless. On x86 platforms, this does not >>>>>>>> seem to matter, as uncached CPU mappings will snoop the caches in any >>>>>>>> case. However, on ARM and arm64, enabling this optimization on a >>>>>>>> platform where NoSnoop is ignored results in loss of coherency, which >>>>>>>> breaks correct operation of the device. Since we have no way of >>>>>>>> detecting whether NoSnoop works or not, just disable this >>>>>>>> optimization entirely for ARM and arm64. >>>>>>>> >>>>>>>> Cc: Christian Koenig <christian.koenig@amd.com> >>>>>>>> Cc: Alex Deucher <alexander.deucher@amd.com> >>>>>>>> Cc: David Zhou <David1.Zhou@amd.com> >>>>>>>> Cc: Huang Rui <ray.huang@amd.com> >>>>>>>> Cc: Junwei Zhang <Jerry.Zhang@amd.com> >>>>>>>> Cc: Michel Daenzer <michel.daenzer@amd.com> >>>>>>>> Cc: David Airlie <airlied@linux.ie> >>>>>>>> Cc: Daniel Vetter <daniel@ffwll.ch> >>>>>>>> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> >>>>>>>> Cc: Maxime Ripard <maxime.ripard@bootlin.com> >>>>>>>> Cc: Sean Paul <sean@poorly.run> >>>>>>>> Cc: Michael Ellerman <mpe@ellerman.id.au> >>>>>>>> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> >>>>>>>> Cc: Will Deacon <will.deacon@arm.com> >>>>>>>> Cc: Christoph Hellwig <hch@infradead.org> >>>>>>>> Cc: Robin Murphy <robin.murphy@arm.com> >>>>>>>> Cc: amd-gfx list <amd-gfx@lists.freedesktop.org> >>>>>>>> Cc: dri-devel <dri-devel@lists.freedesktop.org> >>>>>>>> Reported-by: Carsten Haitzler <Carsten.Haitzler@arm.com> >>>>>>>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> >>>>>>> The subject line should probably read "disable uncached...". >>>>>>> >>>>>> Ugh, of course ... >>>>>> >>>>>>> With that fixed the patch is Reviewed-by: Christian König >>>>>>> <christian.koenig@amd.com>. >>>>>>> >>>>> Same: >>>>> Reviewed-by: Alex Deucher <alexander.deucher@amd.com> >>>>> >>>> Thanks all >>>> >>>> Should I resend the patch with the subject corrected? >>> I will update the subject line and push it upstream through >>> drm-misc-next if nobody objects. >>> >> Wonderful, thanks. > Hi Christian, > > Are you still planning to merge this for v5.1? My bad, only pushed this to our internal branch, but forgot out drm-misc-next. Fixed now, thanks for the reminder. Christian. > > Thanks, > Ard. > _______________________________________________ > amd-gfx mailing list > amd-gfx@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/amd-gfx
On Wed, 6 Feb 2019 at 19:38, Christian König <ckoenig.leichtzumerken@gmail.com> wrote: > > Am 06.02.19 um 18:23 schrieb Ard Biesheuvel: > > On Fri, 25 Jan 2019 at 11:35, Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote: > >> On Fri, 25 Jan 2019 at 12:30, Christian König > >> <ckoenig.leichtzumerken@gmail.com> wrote: > >>> Am 25.01.19 um 09:43 schrieb Ard Biesheuvel: > >>>> On Thu, 24 Jan 2019 at 15:01, Alex Deucher <alexdeucher@gmail.com> wrote: > >>>>> On Thu, Jan 24, 2019 at 9:00 AM Ard Biesheuvel > >>>>> <ard.biesheuvel@linaro.org> wrote: > >>>>>> On Thu, 24 Jan 2019 at 13:31, Koenig, Christian > >>>>>> <Christian.Koenig@amd.com> wrote: > >>>>>>> Am 24.01.19 um 13:06 schrieb Ard Biesheuvel: > >>>>>>>> The DRM driver stack is designed to work with cache coherent devices > >>>>>>>> only, but permits an optimization to be enabled in some cases, where > >>>>>>>> for some buffers, both the CPU and the GPU use uncached mappings, > >>>>>>>> removing the need for DMA snooping and allocation in the CPU caches. > >>>>>>>> > >>>>>>>> The use of uncached GPU mappings relies on the correct implementation > >>>>>>>> of the PCIe NoSnoop TLP attribute by the platform, otherwise the GPU > >>>>>>>> will use cached mappings nonetheless. On x86 platforms, this does not > >>>>>>>> seem to matter, as uncached CPU mappings will snoop the caches in any > >>>>>>>> case. However, on ARM and arm64, enabling this optimization on a > >>>>>>>> platform where NoSnoop is ignored results in loss of coherency, which > >>>>>>>> breaks correct operation of the device. Since we have no way of > >>>>>>>> detecting whether NoSnoop works or not, just disable this > >>>>>>>> optimization entirely for ARM and arm64. > >>>>>>>> > >>>>>>>> Cc: Christian Koenig <christian.koenig@amd.com> > >>>>>>>> Cc: Alex Deucher <alexander.deucher@amd.com> > >>>>>>>> Cc: David Zhou <David1.Zhou@amd.com> > >>>>>>>> Cc: Huang Rui <ray.huang@amd.com> > >>>>>>>> Cc: Junwei Zhang <Jerry.Zhang@amd.com> > >>>>>>>> Cc: Michel Daenzer <michel.daenzer@amd.com> > >>>>>>>> Cc: David Airlie <airlied@linux.ie> > >>>>>>>> Cc: Daniel Vetter <daniel@ffwll.ch> > >>>>>>>> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> > >>>>>>>> Cc: Maxime Ripard <maxime.ripard@bootlin.com> > >>>>>>>> Cc: Sean Paul <sean@poorly.run> > >>>>>>>> Cc: Michael Ellerman <mpe@ellerman.id.au> > >>>>>>>> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> > >>>>>>>> Cc: Will Deacon <will.deacon@arm.com> > >>>>>>>> Cc: Christoph Hellwig <hch@infradead.org> > >>>>>>>> Cc: Robin Murphy <robin.murphy@arm.com> > >>>>>>>> Cc: amd-gfx list <amd-gfx@lists.freedesktop.org> > >>>>>>>> Cc: dri-devel <dri-devel@lists.freedesktop.org> > >>>>>>>> Reported-by: Carsten Haitzler <Carsten.Haitzler@arm.com> > >>>>>>>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> > >>>>>>> The subject line should probably read "disable uncached...". > >>>>>>> > >>>>>> Ugh, of course ... > >>>>>> > >>>>>>> With that fixed the patch is Reviewed-by: Christian König > >>>>>>> <christian.koenig@amd.com>. > >>>>>>> > >>>>> Same: > >>>>> Reviewed-by: Alex Deucher <alexander.deucher@amd.com> > >>>>> > >>>> Thanks all > >>>> > >>>> Should I resend the patch with the subject corrected? > >>> I will update the subject line and push it upstream through > >>> drm-misc-next if nobody objects. > >>> > >> Wonderful, thanks. > > Hi Christian, > > > > Are you still planning to merge this for v5.1? > > My bad, only pushed this to our internal branch, but forgot out > drm-misc-next. > > Fixed now, thanks for the reminder. > Thanks, Does anyone mind if I propose this patch for backporting to v4.19 or earlier once it gets merged for v5.1?
On Thu, Feb 7, 2019 at 10:20 AM Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote: > > On Wed, 6 Feb 2019 at 19:38, Christian König > <ckoenig.leichtzumerken@gmail.com> wrote: > > > > Am 06.02.19 um 18:23 schrieb Ard Biesheuvel: > > > On Fri, 25 Jan 2019 at 11:35, Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote: > > >> On Fri, 25 Jan 2019 at 12:30, Christian König > > >> <ckoenig.leichtzumerken@gmail.com> wrote: > > >>> Am 25.01.19 um 09:43 schrieb Ard Biesheuvel: > > >>>> On Thu, 24 Jan 2019 at 15:01, Alex Deucher <alexdeucher@gmail.com> wrote: > > >>>>> On Thu, Jan 24, 2019 at 9:00 AM Ard Biesheuvel > > >>>>> <ard.biesheuvel@linaro.org> wrote: > > >>>>>> On Thu, 24 Jan 2019 at 13:31, Koenig, Christian > > >>>>>> <Christian.Koenig@amd.com> wrote: > > >>>>>>> Am 24.01.19 um 13:06 schrieb Ard Biesheuvel: > > >>>>>>>> The DRM driver stack is designed to work with cache coherent devices > > >>>>>>>> only, but permits an optimization to be enabled in some cases, where > > >>>>>>>> for some buffers, both the CPU and the GPU use uncached mappings, > > >>>>>>>> removing the need for DMA snooping and allocation in the CPU caches. > > >>>>>>>> > > >>>>>>>> The use of uncached GPU mappings relies on the correct implementation > > >>>>>>>> of the PCIe NoSnoop TLP attribute by the platform, otherwise the GPU > > >>>>>>>> will use cached mappings nonetheless. On x86 platforms, this does not > > >>>>>>>> seem to matter, as uncached CPU mappings will snoop the caches in any > > >>>>>>>> case. However, on ARM and arm64, enabling this optimization on a > > >>>>>>>> platform where NoSnoop is ignored results in loss of coherency, which > > >>>>>>>> breaks correct operation of the device. Since we have no way of > > >>>>>>>> detecting whether NoSnoop works or not, just disable this > > >>>>>>>> optimization entirely for ARM and arm64. > > >>>>>>>> > > >>>>>>>> Cc: Christian Koenig <christian.koenig@amd.com> > > >>>>>>>> Cc: Alex Deucher <alexander.deucher@amd.com> > > >>>>>>>> Cc: David Zhou <David1.Zhou@amd.com> > > >>>>>>>> Cc: Huang Rui <ray.huang@amd.com> > > >>>>>>>> Cc: Junwei Zhang <Jerry.Zhang@amd.com> > > >>>>>>>> Cc: Michel Daenzer <michel.daenzer@amd.com> > > >>>>>>>> Cc: David Airlie <airlied@linux.ie> > > >>>>>>>> Cc: Daniel Vetter <daniel@ffwll.ch> > > >>>>>>>> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> > > >>>>>>>> Cc: Maxime Ripard <maxime.ripard@bootlin.com> > > >>>>>>>> Cc: Sean Paul <sean@poorly.run> > > >>>>>>>> Cc: Michael Ellerman <mpe@ellerman.id.au> > > >>>>>>>> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> > > >>>>>>>> Cc: Will Deacon <will.deacon@arm.com> > > >>>>>>>> Cc: Christoph Hellwig <hch@infradead.org> > > >>>>>>>> Cc: Robin Murphy <robin.murphy@arm.com> > > >>>>>>>> Cc: amd-gfx list <amd-gfx@lists.freedesktop.org> > > >>>>>>>> Cc: dri-devel <dri-devel@lists.freedesktop.org> > > >>>>>>>> Reported-by: Carsten Haitzler <Carsten.Haitzler@arm.com> > > >>>>>>>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> > > >>>>>>> The subject line should probably read "disable uncached...". > > >>>>>>> > > >>>>>> Ugh, of course ... > > >>>>>> > > >>>>>>> With that fixed the patch is Reviewed-by: Christian König > > >>>>>>> <christian.koenig@amd.com>. > > >>>>>>> > > >>>>> Same: > > >>>>> Reviewed-by: Alex Deucher <alexander.deucher@amd.com> > > >>>>> > > >>>> Thanks all > > >>>> > > >>>> Should I resend the patch with the subject corrected? > > >>> I will update the subject line and push it upstream through > > >>> drm-misc-next if nobody objects. > > >>> > > >> Wonderful, thanks. > > > Hi Christian, > > > > > > Are you still planning to merge this for v5.1? > > > > My bad, only pushed this to our internal branch, but forgot out > > drm-misc-next. > > > > Fixed now, thanks for the reminder. > > > > Thanks, > > Does anyone mind if I propose this patch for backporting to v4.19 or > earlier once it gets merged for v5.1? Go for it. I was going to suggest that this should probably go to stable. Alex
On Thu, 7 Feb 2019 at 16:33, Alex Deucher <alexdeucher@gmail.com> wrote: > > On Thu, Feb 7, 2019 at 10:20 AM Ard Biesheuvel > <ard.biesheuvel@linaro.org> wrote: > > > > On Wed, 6 Feb 2019 at 19:38, Christian König > > <ckoenig.leichtzumerken@gmail.com> wrote: > > > > > > Am 06.02.19 um 18:23 schrieb Ard Biesheuvel: > > > > On Fri, 25 Jan 2019 at 11:35, Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote: > > > >> On Fri, 25 Jan 2019 at 12:30, Christian König > > > >> <ckoenig.leichtzumerken@gmail.com> wrote: > > > >>> Am 25.01.19 um 09:43 schrieb Ard Biesheuvel: > > > >>>> On Thu, 24 Jan 2019 at 15:01, Alex Deucher <alexdeucher@gmail.com> wrote: > > > >>>>> On Thu, Jan 24, 2019 at 9:00 AM Ard Biesheuvel > > > >>>>> <ard.biesheuvel@linaro.org> wrote: > > > >>>>>> On Thu, 24 Jan 2019 at 13:31, Koenig, Christian > > > >>>>>> <Christian.Koenig@amd.com> wrote: > > > >>>>>>> Am 24.01.19 um 13:06 schrieb Ard Biesheuvel: > > > >>>>>>>> The DRM driver stack is designed to work with cache coherent devices > > > >>>>>>>> only, but permits an optimization to be enabled in some cases, where > > > >>>>>>>> for some buffers, both the CPU and the GPU use uncached mappings, > > > >>>>>>>> removing the need for DMA snooping and allocation in the CPU caches. > > > >>>>>>>> > > > >>>>>>>> The use of uncached GPU mappings relies on the correct implementation > > > >>>>>>>> of the PCIe NoSnoop TLP attribute by the platform, otherwise the GPU > > > >>>>>>>> will use cached mappings nonetheless. On x86 platforms, this does not > > > >>>>>>>> seem to matter, as uncached CPU mappings will snoop the caches in any > > > >>>>>>>> case. However, on ARM and arm64, enabling this optimization on a > > > >>>>>>>> platform where NoSnoop is ignored results in loss of coherency, which > > > >>>>>>>> breaks correct operation of the device. Since we have no way of > > > >>>>>>>> detecting whether NoSnoop works or not, just disable this > > > >>>>>>>> optimization entirely for ARM and arm64. > > > >>>>>>>> > > > >>>>>>>> Cc: Christian Koenig <christian.koenig@amd.com> > > > >>>>>>>> Cc: Alex Deucher <alexander.deucher@amd.com> > > > >>>>>>>> Cc: David Zhou <David1.Zhou@amd.com> > > > >>>>>>>> Cc: Huang Rui <ray.huang@amd.com> > > > >>>>>>>> Cc: Junwei Zhang <Jerry.Zhang@amd.com> > > > >>>>>>>> Cc: Michel Daenzer <michel.daenzer@amd.com> > > > >>>>>>>> Cc: David Airlie <airlied@linux.ie> > > > >>>>>>>> Cc: Daniel Vetter <daniel@ffwll.ch> > > > >>>>>>>> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> > > > >>>>>>>> Cc: Maxime Ripard <maxime.ripard@bootlin.com> > > > >>>>>>>> Cc: Sean Paul <sean@poorly.run> > > > >>>>>>>> Cc: Michael Ellerman <mpe@ellerman.id.au> > > > >>>>>>>> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> > > > >>>>>>>> Cc: Will Deacon <will.deacon@arm.com> > > > >>>>>>>> Cc: Christoph Hellwig <hch@infradead.org> > > > >>>>>>>> Cc: Robin Murphy <robin.murphy@arm.com> > > > >>>>>>>> Cc: amd-gfx list <amd-gfx@lists.freedesktop.org> > > > >>>>>>>> Cc: dri-devel <dri-devel@lists.freedesktop.org> > > > >>>>>>>> Reported-by: Carsten Haitzler <Carsten.Haitzler@arm.com> > > > >>>>>>>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> > > > >>>>>>> The subject line should probably read "disable uncached...". > > > >>>>>>> > > > >>>>>> Ugh, of course ... > > > >>>>>> > > > >>>>>>> With that fixed the patch is Reviewed-by: Christian König > > > >>>>>>> <christian.koenig@amd.com>. > > > >>>>>>> > > > >>>>> Same: > > > >>>>> Reviewed-by: Alex Deucher <alexander.deucher@amd.com> > > > >>>>> > > > >>>> Thanks all > > > >>>> > > > >>>> Should I resend the patch with the subject corrected? > > > >>> I will update the subject line and push it upstream through > > > >>> drm-misc-next if nobody objects. > > > >>> > > > >> Wonderful, thanks. > > > > Hi Christian, > > > > > > > > Are you still planning to merge this for v5.1? > > > > > > My bad, only pushed this to our internal branch, but forgot out > > > drm-misc-next. > > > > > > Fixed now, thanks for the reminder. > > > > > > > Thanks, > > > > Does anyone mind if I propose this patch for backporting to v4.19 or > > earlier once it gets merged for v5.1? > > Go for it. I was going to suggest that this should probably go to stable. > Excellent. Note that I actually prefer sending it manually rather than let Greg or Sasha pick it up automatically, given that they are usually a bit trigger happy, i.e., patches tend to get backported before anyone has had a chance to actually check that it doesn't break anything in mainline. In other words, please don't add a cc -stable or fixes tag. I will track it myself instead. Thanks, Ard.
diff --git a/include/drm/drm_cache.h b/include/drm/drm_cache.h index bfe1639df02d..97fc498dc767 100644 --- a/include/drm/drm_cache.h +++ b/include/drm/drm_cache.h @@ -47,6 +47,24 @@ static inline bool drm_arch_can_wc_memory(void) return false; #elif defined(CONFIG_MIPS) && defined(CONFIG_CPU_LOONGSON3) return false; +#elif defined(CONFIG_ARM) || defined(CONFIG_ARM64) + /* + * The DRM driver stack is designed to work with cache coherent devices + * only, but permits an optimization to be enabled in some cases, where + * for some buffers, both the CPU and the GPU use uncached mappings, + * removing the need for DMA snooping and allocation in the CPU caches. + * + * The use of uncached GPU mappings relies on the correct implementation + * of the PCIe NoSnoop TLP attribute by the platform, otherwise the GPU + * will use cached mappings nonetheless. On x86 platforms, this does not + * seem to matter, as uncached CPU mappings will snoop the caches in any + * case. However, on ARM and arm64, enabling this optimization on a + * platform where NoSnoop is ignored results in loss of coherency, which + * breaks correct operation of the device. Since we have no way of + * detecting whether NoSnoop works or not, just disable this + * optimization entirely for ARM and arm64. + */ + return false; #else return true; #endif
The DRM driver stack is designed to work with cache coherent devices only, but permits an optimization to be enabled in some cases, where for some buffers, both the CPU and the GPU use uncached mappings, removing the need for DMA snooping and allocation in the CPU caches. The use of uncached GPU mappings relies on the correct implementation of the PCIe NoSnoop TLP attribute by the platform, otherwise the GPU will use cached mappings nonetheless. On x86 platforms, this does not seem to matter, as uncached CPU mappings will snoop the caches in any case. However, on ARM and arm64, enabling this optimization on a platform where NoSnoop is ignored results in loss of coherency, which breaks correct operation of the device. Since we have no way of detecting whether NoSnoop works or not, just disable this optimization entirely for ARM and arm64. Cc: Christian Koenig <christian.koenig@amd.com> Cc: Alex Deucher <alexander.deucher@amd.com> Cc: David Zhou <David1.Zhou@amd.com> Cc: Huang Rui <ray.huang@amd.com> Cc: Junwei Zhang <Jerry.Zhang@amd.com> Cc: Michel Daenzer <michel.daenzer@amd.com> Cc: David Airlie <airlied@linux.ie> Cc: Daniel Vetter <daniel@ffwll.ch> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Cc: Maxime Ripard <maxime.ripard@bootlin.com> Cc: Sean Paul <sean@poorly.run> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Will Deacon <will.deacon@arm.com> Cc: Christoph Hellwig <hch@infradead.org> Cc: Robin Murphy <robin.murphy@arm.com> Cc: amd-gfx list <amd-gfx@lists.freedesktop.org> Cc: dri-devel <dri-devel@lists.freedesktop.org> Reported-by: Carsten Haitzler <Carsten.Haitzler@arm.com> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> --- include/drm/drm_cache.h | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) -- 2.20.1