| Message ID | 20180214134340.17242-5-jbrunet@baylibre.com |
|---|---|
| State | New |
| Headers | show |
| Series | clk: helpers and fixes | expand |
Hi Jerome, On 2018-02-14 14:43, Jerome Brunet wrote: > The orphan clocks reparents should migrate any existing count from the > orphan clock to its new acestor clocks, otherwise we may have > inconsistent counts in the tree and end-up with gated critical clocks > > Assuming we have two clocks, A and B. > * Clock A has CLK_IS_CRITICAL flag set. > * Clock B is an ancestor of A which can gate. Clock B gate is left > enabled by the bootloader. > > Step 1: Clock A is registered. Since it is a critical clock, it is > enabled. The clock being still an orphan, no parent are enabled. > > Step 2: Clock B is registered and reparented to clock A (potentially > through several other clocks). We are now in situation where the enable > count of clock A is 1 while the enable count of its ancestors is 0, which > is not good. > > Step 3: in lateinit, clk_disable_unused() is called, the enable_count of > clock B being 0, clock B is gated and and critical clock A actually gets > disabled. > > This situation was found while adding fdiv_clk gates to the meson8b > platform. These clocks parent clk81 critical clock, which is the mother > of all peripheral clocks in this system. Because of the issue described > here, the system is crashing when clk_disable_unused() is called. > > The situation is solved by reverting > commit f8f8f1d04494 ("clk: Don't touch hardware when reparenting during registration"). > To avoid breaking again the situation described in this commit > description, enabling critical clock should be done before walking the > orphan list. This way, a parent critical clock may not be accidentally > disabled due to the CLK_OPS_PARENT_ENABLE mechanism. > > Fixes: f8f8f1d04494 ("clk: Don't touch hardware when reparenting during registration") > Cc: Stephen Boyd <sboyd@codeaurora.org> > Cc: Shawn Guo <shawnguo@kernel.org> > Cc: Dong Aisheng <aisheng.dong@nxp.com> > Signed-off-by: Jerome Brunet <jbrunet@baylibre.com> Tested-by: Marek Szyprowski <m.szyprowski@samsung.com> This patch fixes kernel oops on Exynos5422-based boards (Odroid XU3/XU4) mentioned in the following threads: https://patchwork.kernel.org/patch/10185357/ https://www.spinics.net/lists/linux-samsung-soc/msg61766.html > --- > drivers/clk/clk.c | 37 +++++++++++++++++++++---------------- > 1 file changed, 21 insertions(+), 16 deletions(-) > > diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c > index a4b4e4d6df5e..cca05ea2c058 100644 > --- a/drivers/clk/clk.c > +++ b/drivers/clk/clk.c > @@ -2969,23 +2969,38 @@ static int __clk_core_init(struct clk_core *core) > rate = 0; > core->rate = core->req_rate = rate; > > + /* > + * Enable CLK_IS_CRITICAL clocks so newly added critical clocks > + * don't get accidentally disabled when walking the orphan tree and > + * reparenting clocks > + */ > + if (core->flags & CLK_IS_CRITICAL) { > + unsigned long flags; > + > + clk_core_prepare(core); > + > + flags = clk_enable_lock(); > + clk_core_enable(core); > + clk_enable_unlock(flags); > + } > + > /* > * walk the list of orphan clocks and reparent any that newly finds a > * parent. > */ > hlist_for_each_entry_safe(orphan, tmp2, &clk_orphan_list, child_node) { > struct clk_core *parent = __clk_init_parent(orphan); > - unsigned long flags; > > /* > - * we could call __clk_set_parent, but that would result in a > - * redundant call to the .set_rate op, if it exists > + * We need to use __clk_set_parent_before() and _after() to > + * to properly migrate any prepare/enable count of the orphan > + * clock. This is important for CLK_IS_CRITICAL clocks, which > + * are enabled during init but might not have a parent yet. > */ > if (parent) { > /* update the clk tree topology */ > - flags = clk_enable_lock(); > - clk_reparent(orphan, parent); > - clk_enable_unlock(flags); > + __clk_set_parent_before(orphan, parent); > + __clk_set_parent_after(orphan, parent, NULL); > __clk_recalc_accuracies(orphan); > __clk_recalc_rates(orphan, 0); > } > @@ -3002,16 +3017,6 @@ static int __clk_core_init(struct clk_core *core) > if (core->ops->init) > core->ops->init(core->hw); > > - if (core->flags & CLK_IS_CRITICAL) { > - unsigned long flags; > - > - clk_core_prepare(core); > - > - flags = clk_enable_lock(); > - clk_core_enable(core); > - clk_enable_unlock(flags); > - } > - > kref_init(&core->ref); > out: > clk_pm_runtime_put(core); Best regards -- Marek Szyprowski, PhD Samsung R&D Institute Poland
Am Mittwoch, 14. Februar 2018, 14:43:36 CET schrieb Jerome Brunet: > The orphan clocks reparents should migrate any existing count from the > orphan clock to its new acestor clocks, otherwise we may have > inconsistent counts in the tree and end-up with gated critical clocks > > Assuming we have two clocks, A and B. > * Clock A has CLK_IS_CRITICAL flag set. > * Clock B is an ancestor of A which can gate. Clock B gate is left > enabled by the bootloader. > > Step 1: Clock A is registered. Since it is a critical clock, it is > enabled. The clock being still an orphan, no parent are enabled. > > Step 2: Clock B is registered and reparented to clock A (potentially > through several other clocks). We are now in situation where the enable > count of clock A is 1 while the enable count of its ancestors is 0, which > is not good. > > Step 3: in lateinit, clk_disable_unused() is called, the enable_count of > clock B being 0, clock B is gated and and critical clock A actually gets > disabled. > > This situation was found while adding fdiv_clk gates to the meson8b > platform. These clocks parent clk81 critical clock, which is the mother > of all peripheral clocks in this system. Because of the issue described > here, the system is crashing when clk_disable_unused() is called. > > The situation is solved by reverting > commit f8f8f1d04494 ("clk: Don't touch hardware when reparenting during > registration"). To avoid breaking again the situation described in this > commit > description, enabling critical clock should be done before walking the > orphan list. This way, a parent critical clock may not be accidentally > disabled due to the CLK_OPS_PARENT_ENABLE mechanism. > > Fixes: f8f8f1d04494 ("clk: Don't touch hardware when reparenting during > registration") Cc: Stephen Boyd <sboyd@codeaurora.org> > Cc: Shawn Guo <shawnguo@kernel.org> > Cc: Dong Aisheng <aisheng.dong@nxp.com> > Signed-off-by: Jerome Brunet <jbrunet@baylibre.com> On a rk3288-veyron Chromebook Tested-by: Heiko Stuebner <heiko@sntech.de> This made the hdmi on the machine work again with 4.16-rc1 . (hdmi-cec clock is sourced from the i2c connected pmic which provides the 32kHz clock needed) So it would be really cool if this could make it into 4.16-rc :-) Heiko
Hi All, On 2018-02-15 13:55, Marek Szyprowski wrote: > Hi Jerome, > > On 2018-02-14 14:43, Jerome Brunet wrote: >> The orphan clocks reparents should migrate any existing count from the >> orphan clock to its new acestor clocks, otherwise we may have >> inconsistent counts in the tree and end-up with gated critical clocks >> >> Assuming we have two clocks, A and B. >> * Clock A has CLK_IS_CRITICAL flag set. >> * Clock B is an ancestor of A which can gate. Clock B gate is left >> enabled by the bootloader. >> >> Step 1: Clock A is registered. Since it is a critical clock, it is >> enabled. The clock being still an orphan, no parent are enabled. >> >> Step 2: Clock B is registered and reparented to clock A (potentially >> through several other clocks). We are now in situation where the enable >> count of clock A is 1 while the enable count of its ancestors is 0, >> which >> is not good. >> >> Step 3: in lateinit, clk_disable_unused() is called, the enable_count of >> clock B being 0, clock B is gated and and critical clock A actually gets >> disabled. >> >> This situation was found while adding fdiv_clk gates to the meson8b >> platform. These clocks parent clk81 critical clock, which is the mother >> of all peripheral clocks in this system. Because of the issue described >> here, the system is crashing when clk_disable_unused() is called. >> >> The situation is solved by reverting >> commit f8f8f1d04494 ("clk: Don't touch hardware when reparenting >> during registration"). >> To avoid breaking again the situation described in this commit >> description, enabling critical clock should be done before walking the >> orphan list. This way, a parent critical clock may not be accidentally >> disabled due to the CLK_OPS_PARENT_ENABLE mechanism. >> >> Fixes: f8f8f1d04494 ("clk: Don't touch hardware when reparenting >> during registration") >> Cc: Stephen Boyd <sboyd@codeaurora.org> >> Cc: Shawn Guo <shawnguo@kernel.org> >> Cc: Dong Aisheng <aisheng.dong@nxp.com> >> Signed-off-by: Jerome Brunet <jbrunet@baylibre.com> > > Tested-by: Marek Szyprowski <m.szyprowski@samsung.com> > > This patch fixes kernel oops on Exynos5422-based boards (Odroid XU3/XU4) > mentioned in the following threads: > https://patchwork.kernel.org/patch/10185357/ > https://www.spinics.net/lists/linux-samsung-soc/msg61766.html Stephen, Michael: v4.16-rc4 is out today and this regression (which got merged on 22 Dec 2017) is still not fixed yet... Is there a chance to get it into final v4.16 release? >> --- >> drivers/clk/clk.c | 37 +++++++++++++++++++++---------------- >> 1 file changed, 21 insertions(+), 16 deletions(-) >> >> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c >> index a4b4e4d6df5e..cca05ea2c058 100644 >> --- a/drivers/clk/clk.c >> +++ b/drivers/clk/clk.c >> @@ -2969,23 +2969,38 @@ static int __clk_core_init(struct clk_core >> *core) >> rate = 0; >> core->rate = core->req_rate = rate; >> + /* >> + * Enable CLK_IS_CRITICAL clocks so newly added critical clocks >> + * don't get accidentally disabled when walking the orphan tree and >> + * reparenting clocks >> + */ >> + if (core->flags & CLK_IS_CRITICAL) { >> + unsigned long flags; >> + >> + clk_core_prepare(core); >> + >> + flags = clk_enable_lock(); >> + clk_core_enable(core); >> + clk_enable_unlock(flags); >> + } >> + >> /* >> * walk the list of orphan clocks and reparent any that newly >> finds a >> * parent. >> */ >> hlist_for_each_entry_safe(orphan, tmp2, &clk_orphan_list, >> child_node) { >> struct clk_core *parent = __clk_init_parent(orphan); >> - unsigned long flags; >> /* >> - * we could call __clk_set_parent, but that would result in a >> - * redundant call to the .set_rate op, if it exists >> + * We need to use __clk_set_parent_before() and _after() to >> + * to properly migrate any prepare/enable count of the orphan >> + * clock. This is important for CLK_IS_CRITICAL clocks, which >> + * are enabled during init but might not have a parent yet. >> */ >> if (parent) { >> /* update the clk tree topology */ >> - flags = clk_enable_lock(); >> - clk_reparent(orphan, parent); >> - clk_enable_unlock(flags); >> + __clk_set_parent_before(orphan, parent); >> + __clk_set_parent_after(orphan, parent, NULL); >> __clk_recalc_accuracies(orphan); >> __clk_recalc_rates(orphan, 0); >> } >> @@ -3002,16 +3017,6 @@ static int __clk_core_init(struct clk_core *core) >> if (core->ops->init) >> core->ops->init(core->hw); >> - if (core->flags & CLK_IS_CRITICAL) { >> - unsigned long flags; >> - >> - clk_core_prepare(core); >> - >> - flags = clk_enable_lock(); >> - clk_core_enable(core); >> - clk_enable_unlock(flags); >> - } >> - >> kref_init(&core->ref); >> out: >> clk_pm_runtime_put(core); > Best regards -- Marek Szyprowski, PhD Samsung R&D Institute Poland
Excerpts from Heiko Stübner's message of February 15, 2018 1:01 pm: > Am Mittwoch, 14. Februar 2018, 14:43:36 CET schrieb Jerome Brunet: >> The orphan clocks reparents should migrate any existing count from the >> orphan clock to its new acestor clocks, otherwise we may have >> inconsistent counts in the tree and end-up with gated critical clocks >> >> Assuming we have two clocks, A and B. >> * Clock A has CLK_IS_CRITICAL flag set. >> * Clock B is an ancestor of A which can gate. Clock B gate is left >> enabled by the bootloader. >> >> Step 1: Clock A is registered. Since it is a critical clock, it is >> enabled. The clock being still an orphan, no parent are enabled. >> >> Step 2: Clock B is registered and reparented to clock A (potentially >> through several other clocks). We are now in situation where the enable >> count of clock A is 1 while the enable count of its ancestors is 0, which >> is not good. >> >> Step 3: in lateinit, clk_disable_unused() is called, the enable_count of >> clock B being 0, clock B is gated and and critical clock A actually gets >> disabled. >> >> This situation was found while adding fdiv_clk gates to the meson8b >> platform. These clocks parent clk81 critical clock, which is the mother >> of all peripheral clocks in this system. Because of the issue described >> here, the system is crashing when clk_disable_unused() is called. >> >> The situation is solved by reverting >> commit f8f8f1d04494 ("clk: Don't touch hardware when reparenting during >> registration"). To avoid breaking again the situation described in this >> commit >> description, enabling critical clock should be done before walking the >> orphan list. This way, a parent critical clock may not be accidentally >> disabled due to the CLK_OPS_PARENT_ENABLE mechanism. >> >> Fixes: f8f8f1d04494 ("clk: Don't touch hardware when reparenting during >> registration") Cc: Stephen Boyd <sboyd@codeaurora.org> >> Cc: Shawn Guo <shawnguo@kernel.org> >> Cc: Dong Aisheng <aisheng.dong@nxp.com> >> Signed-off-by: Jerome Brunet <jbrunet@baylibre.com> > > On a rk3288-veyron Chromebook > Tested-by: Heiko Stuebner <heiko@sntech.de> > > This made the hdmi on the machine work again with 4.16-rc1 . > (hdmi-cec clock is sourced from the i2c connected pmic which provides > the 32kHz clock needed) > > So it would be really cool if this could make it into 4.16-rc :-) I separated this patch out into clk-fixes to be set for -rc5 or -rc6. Regards, Mike > > > Heiko >
diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c index a4b4e4d6df5e..cca05ea2c058 100644 --- a/drivers/clk/clk.c +++ b/drivers/clk/clk.c @@ -2969,23 +2969,38 @@ static int __clk_core_init(struct clk_core *core) rate = 0; core->rate = core->req_rate = rate; + /* + * Enable CLK_IS_CRITICAL clocks so newly added critical clocks + * don't get accidentally disabled when walking the orphan tree and + * reparenting clocks + */ + if (core->flags & CLK_IS_CRITICAL) { + unsigned long flags; + + clk_core_prepare(core); + + flags = clk_enable_lock(); + clk_core_enable(core); + clk_enable_unlock(flags); + } + /* * walk the list of orphan clocks and reparent any that newly finds a * parent. */ hlist_for_each_entry_safe(orphan, tmp2, &clk_orphan_list, child_node) { struct clk_core *parent = __clk_init_parent(orphan); - unsigned long flags; /* - * we could call __clk_set_parent, but that would result in a - * redundant call to the .set_rate op, if it exists + * We need to use __clk_set_parent_before() and _after() to + * to properly migrate any prepare/enable count of the orphan + * clock. This is important for CLK_IS_CRITICAL clocks, which + * are enabled during init but might not have a parent yet. */ if (parent) { /* update the clk tree topology */ - flags = clk_enable_lock(); - clk_reparent(orphan, parent); - clk_enable_unlock(flags); + __clk_set_parent_before(orphan, parent); + __clk_set_parent_after(orphan, parent, NULL); __clk_recalc_accuracies(orphan); __clk_recalc_rates(orphan, 0); } @@ -3002,16 +3017,6 @@ static int __clk_core_init(struct clk_core *core) if (core->ops->init) core->ops->init(core->hw); - if (core->flags & CLK_IS_CRITICAL) { - unsigned long flags; - - clk_core_prepare(core); - - flags = clk_enable_lock(); - clk_core_enable(core); - clk_enable_unlock(flags); - } - kref_init(&core->ref); out: clk_pm_runtime_put(core);
The orphan clocks reparents should migrate any existing count from the orphan clock to its new acestor clocks, otherwise we may have inconsistent counts in the tree and end-up with gated critical clocks Assuming we have two clocks, A and B. * Clock A has CLK_IS_CRITICAL flag set. * Clock B is an ancestor of A which can gate. Clock B gate is left enabled by the bootloader. Step 1: Clock A is registered. Since it is a critical clock, it is enabled. The clock being still an orphan, no parent are enabled. Step 2: Clock B is registered and reparented to clock A (potentially through several other clocks). We are now in situation where the enable count of clock A is 1 while the enable count of its ancestors is 0, which is not good. Step 3: in lateinit, clk_disable_unused() is called, the enable_count of clock B being 0, clock B is gated and and critical clock A actually gets disabled. This situation was found while adding fdiv_clk gates to the meson8b platform. These clocks parent clk81 critical clock, which is the mother of all peripheral clocks in this system. Because of the issue described here, the system is crashing when clk_disable_unused() is called. The situation is solved by reverting commit f8f8f1d04494 ("clk: Don't touch hardware when reparenting during registration"). To avoid breaking again the situation described in this commit description, enabling critical clock should be done before walking the orphan list. This way, a parent critical clock may not be accidentally disabled due to the CLK_OPS_PARENT_ENABLE mechanism. Fixes: f8f8f1d04494 ("clk: Don't touch hardware when reparenting during registration") Cc: Stephen Boyd <sboyd@codeaurora.org> Cc: Shawn Guo <shawnguo@kernel.org> Cc: Dong Aisheng <aisheng.dong@nxp.com> Signed-off-by: Jerome Brunet <jbrunet@baylibre.com> --- drivers/clk/clk.c | 37 +++++++++++++++++++++---------------- 1 file changed, 21 insertions(+), 16 deletions(-) -- 2.14.3