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Groups > linux.kernel > #1675564 > unrolled thread
| Started by | Dirk Behme <dirk.behme@de.bosch.com> |
|---|---|
| First post | 2017-06-27 13:20 +0200 |
| Last post | 2017-07-03 14:10 +0200 |
| Articles | 3 — 2 participants |
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Re: [PATCH 2/3] clk: WARN_ON about to disable a critical clock Dirk Behme <dirk.behme@de.bosch.com> - 2017-06-27 13:20 +0200
Re: [PATCH 2/3] clk: WARN_ON about to disable a critical clock Lee Jones <lee.jones@linaro.org> - 2017-07-03 14:00 +0200
Re: [PATCH 2/3] clk: WARN_ON about to disable a critical clock Dirk Behme <dirk.behme@de.bosch.com> - 2017-07-03 14:10 +0200
| From | Dirk Behme <dirk.behme@de.bosch.com> |
|---|---|
| Date | 2017-06-27 13:20 +0200 |
| Subject | Re: [PATCH 2/3] clk: WARN_ON about to disable a critical clock |
| Message-ID | <tWWHg-8aL-23@gated-at.bofh.it> |
On 11.02.2016 01:43, Michael Turquette wrote:
> Quoting Lee Jones (2016-01-18 06:28:50)
>> Signed-off-by: Lee Jones <lee.jones@linaro.org>
>
> Looks good to me.
>
> Regards,
> Mike
>
>> ---
>> drivers/clk/clk.c | 6 ++++++
>> 1 file changed, 6 insertions(+)
>>
>> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
>> index 835cb85..178b364 100644
>> --- a/drivers/clk/clk.c
>> +++ b/drivers/clk/clk.c
>> @@ -575,6 +575,9 @@ static void clk_core_unprepare(struct clk_core *core)
>> if (WARN_ON(core->prepare_count == 0))
>> return;
>>
>> + if (WARN_ON(core->prepare_count == 1 && core->flags & CLK_IS_CRITICAL))
>> + return;
>> +
>> if (--core->prepare_count > 0)
>> return;
>>
>> @@ -680,6 +683,9 @@ static void clk_core_disable(struct clk_core *core)
>> if (WARN_ON(core->enable_count == 0))
>> return;
>>
>> + if (WARN_ON(core->enable_count == 1 && core->flags & CLK_IS_CRITICAL))
>> + return;
>> +
>> if (--core->enable_count > 0)
>> return;
I have a question regarding this patch, which is mainline meanwhile [1]:
Having the following clock configuration:
|--> child clk '1' (crit)
clk source --> parent clk 'A' (crit) -->|
|--> child clk '2'
Clock '2' might be used, or not. It might be disabled or not. It doesn't
matter. Clock '1' is not allowed to be disabled. Therefore its marked as
critical.
Parent clock 'A' is marked as critical because its not allowed to be
disabled, even if the enable_count of all child clocks is 0. To avoid
that by disabling parent clock 'A' the child clock '1' is disabled, too,
whats not allowed as its marked as critical.
Now, child clock '2' is used and enabled & disabled continuously by a
(SPI) driver. What is ok. But:
Disabling child clock '2' results in the attempt to disable parent clock
'A', too, which has correct enable_count 1 (from enabling the child
'2'). What results
a) in the WARN_ON output
and
b) enable_count of 'A' never decreases to 0. Being off by one after the
WARN_ON
It sounds like both is wrong for a configuration like above.
Opinions or proposal how to fix/change this?
Best regards
Dirk
[1]
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/clk/clk.c?id=2e20fbf592621b2c2aeddd82e0fa3dad053cce03
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| From | Lee Jones <lee.jones@linaro.org> |
|---|---|
| Date | 2017-07-03 14:00 +0200 |
| Message-ID | <tZ8bf-R2-1@gated-at.bofh.it> |
| In reply to | #1675564 |
On Tue, 27 Jun 2017, Dirk Behme wrote: > On 11.02.2016 01:43, Michael Turquette wrote: > > Quoting Lee Jones (2016-01-18 06:28:50) > > > Signed-off-by: Lee Jones <lee.jones@linaro.org> > > > > Looks good to me. > > > > Regards, > > Mike > > > > > --- > > > drivers/clk/clk.c | 6 ++++++ > > > 1 file changed, 6 insertions(+) > > > > > > diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c > > > index 835cb85..178b364 100644 > > > --- a/drivers/clk/clk.c > > > +++ b/drivers/clk/clk.c > > > @@ -575,6 +575,9 @@ static void clk_core_unprepare(struct clk_core *core) > > > if (WARN_ON(core->prepare_count == 0)) > > > return; > > > + if (WARN_ON(core->prepare_count == 1 && core->flags & CLK_IS_CRITICAL)) > > > + return; > > > + > > > if (--core->prepare_count > 0) > > > return; > > > @@ -680,6 +683,9 @@ static void clk_core_disable(struct clk_core *core) > > > if (WARN_ON(core->enable_count == 0)) > > > return; > > > + if (WARN_ON(core->enable_count == 1 && core->flags & CLK_IS_CRITICAL)) > > > + return; > > > + > > > if (--core->enable_count > 0) > > > return; > > > I have a question regarding this patch, which is mainline meanwhile [1]: > > Having the following clock configuration: > > |--> child clk '1' (crit) > clk source --> parent clk 'A' (crit) -->| > |--> child clk '2' > > > Clock '2' might be used, or not. It might be disabled or not. It doesn't > matter. Clock '1' is not allowed to be disabled. Therefore its marked as > critical. > > Parent clock 'A' is marked as critical because its not allowed to be > disabled, even if the enable_count of all child clocks is 0. To avoid that > by disabling parent clock 'A' the child clock '1' is disabled, too, whats > not allowed as its marked as critical. > > > Now, child clock '2' is used and enabled & disabled continuously by a (SPI) > driver. What is ok. But: > > Disabling child clock '2' results in the attempt to disable parent clock > 'A', too, which has correct enable_count 1 (from enabling the child '2'). > What results > > a) in the WARN_ON output > > and > > b) enable_count of 'A' never decreases to 0. Being off by one after the > WARN_ON > > > It sounds like both is wrong for a configuration like above. Clock A still has one user, Clock 1. Why is that wrong? > Opinions or proposal how to fix/change this? > > > Best regards > > Dirk > > [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/clk/clk.c?id=2e20fbf592621b2c2aeddd82e0fa3dad053cce03 -- Lee Jones Linaro STMicroelectronics Landing Team Lead Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog
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| From | Dirk Behme <dirk.behme@de.bosch.com> |
|---|---|
| Date | 2017-07-03 14:10 +0200 |
| Message-ID | <tZ8kW-1aZ-25@gated-at.bofh.it> |
| In reply to | #1679935 |
On 03.07.2017 13:53, Lee Jones wrote: > On Tue, 27 Jun 2017, Dirk Behme wrote: > >> On 11.02.2016 01:43, Michael Turquette wrote: >>> Quoting Lee Jones (2016-01-18 06:28:50) >>>> Signed-off-by: Lee Jones <lee.jones@linaro.org> >>> >>> Looks good to me. >>> >>> Regards, >>> Mike >>> >>>> --- >>>> drivers/clk/clk.c | 6 ++++++ >>>> 1 file changed, 6 insertions(+) >>>> >>>> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c >>>> index 835cb85..178b364 100644 >>>> --- a/drivers/clk/clk.c >>>> +++ b/drivers/clk/clk.c >>>> @@ -575,6 +575,9 @@ static void clk_core_unprepare(struct clk_core *core) >>>> if (WARN_ON(core->prepare_count == 0)) >>>> return; >>>> + if (WARN_ON(core->prepare_count == 1 && core->flags & CLK_IS_CRITICAL)) >>>> + return; >>>> + >>>> if (--core->prepare_count > 0) >>>> return; >>>> @@ -680,6 +683,9 @@ static void clk_core_disable(struct clk_core *core) >>>> if (WARN_ON(core->enable_count == 0)) >>>> return; >>>> + if (WARN_ON(core->enable_count == 1 && core->flags & CLK_IS_CRITICAL)) >>>> + return; >>>> + >>>> if (--core->enable_count > 0) >>>> return; >> >> >> I have a question regarding this patch, which is mainline meanwhile [1]: >> >> Having the following clock configuration: >> >> |--> child clk '1' (crit) >> clk source --> parent clk 'A' (crit) -->| >> |--> child clk '2' >> >> >> Clock '2' might be used, or not. It might be disabled or not. It doesn't >> matter. Clock '1' is not allowed to be disabled. Therefore its marked as >> critical. >> >> Parent clock 'A' is marked as critical because its not allowed to be >> disabled, even if the enable_count of all child clocks is 0. To avoid that >> by disabling parent clock 'A' the child clock '1' is disabled, too, whats >> not allowed as its marked as critical. >> >> >> Now, child clock '2' is used and enabled & disabled continuously by a (SPI) >> driver. What is ok. But: >> >> Disabling child clock '2' results in the attempt to disable parent clock >> 'A', too, which has correct enable_count 1 (from enabling the child '2'). >> What results >> >> a) in the WARN_ON output >> >> and >> >> b) enable_count of 'A' never decreases to 0. Being off by one after the >> WARN_ON >> >> >> It sounds like both is wrong for a configuration like above. > > Clock A still has one user, Clock 1. > > Why is that wrong? Because clock 1 is not a (Linux kernel clock framework) used clock. Its enable count is 0. So from Linux kernel (clock framework) point of view clock 1 is unused. The increase/decrease of enable count of parent clock A is only driven by the Linux kernel usage of clock 2. Best regards Dirk >> Opinions or proposal how to fix/change this? >> >> >> Best regards >> >> Dirk >> >> [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/clk/clk.c?id=2e20fbf592621b2c2aeddd82e0fa3dad053cce03
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