PM / Domains: Correct comment in irq_safe_dev_in_no_sleep_domain()
diff mbox

Message ID 1485878463-1672-1-git-send-email-ulf.hansson@linaro.org
State Mainlined
Delegated to: Rafael Wysocki
Headers show

Commit Message

Ulf Hansson Jan. 31, 2017, 4:01 p.m. UTC
The earlier comment stated that the dev_warn_once() was going to be printed
once per device. Let's fix that, as dev_warn_once() is printed only once,
no matter of the device.

Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
---
 drivers/base/power/domain.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Geert Uytterhoeven Jan. 31, 2017, 4:17 p.m. UTC | #1
Hi Ulf,

On Tue, Jan 31, 2017 at 5:01 PM, Ulf Hansson <ulf.hansson@linaro.org> wrote:
> The earlier comment stated that the dev_warn_once() was going to be printed
> once per device. Let's fix that, as dev_warn_once() is printed only once,
> no matter of the device.

While I agree this makes the comment match the code, I think we would serve
the users better by printing the warning once per PM domain.
Currently the user cannot know if two or more PM domains cannot be powered
off due to IRQ safe devices.

Perhaps a flag can be added to generic_pm_domain.flags to remember
that the warning has been printed before?

> Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
> ---
>  drivers/base/power/domain.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> index 6b23d82..271e208 100644
> --- a/drivers/base/power/domain.c
> +++ b/drivers/base/power/domain.c
> @@ -130,7 +130,7 @@ static inline bool irq_safe_dev_in_no_sleep_domain(struct device *dev,
>
>         ret = pm_runtime_is_irq_safe(dev) && !genpd_is_irq_safe(genpd);
>
> -       /* Warn once for each IRQ safe dev in no sleep domain */
> +       /* Warn once if IRQ safe dev in no sleep domain */
>         if (ret)
>                 dev_warn_once(dev, "PM domain %s will not be powered off\n",
>                                 genpd->name);

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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Lina Iyer Jan. 31, 2017, 4:17 p.m. UTC | #2
On Tue, Jan 31 2017 at 09:01 -0700, Ulf Hansson wrote:
>The earlier comment stated that the dev_warn_once() was going to be printed
>once per device. Let's fix that, as dev_warn_once() is printed only once,
>no matter of the device.
>
>Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
>Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

Acked-by: Lina Iyer <lina.iyer@linaro.org>

>---
> drivers/base/power/domain.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
>diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
>index 6b23d82..271e208 100644
>--- a/drivers/base/power/domain.c
>+++ b/drivers/base/power/domain.c
>@@ -130,7 +130,7 @@ static inline bool irq_safe_dev_in_no_sleep_domain(struct device *dev,
>
> 	ret = pm_runtime_is_irq_safe(dev) && !genpd_is_irq_safe(genpd);
>
>-	/* Warn once for each IRQ safe dev in no sleep domain */
>+	/* Warn once if IRQ safe dev in no sleep domain */
> 	if (ret)
> 		dev_warn_once(dev, "PM domain %s will not be powered off\n",
> 				genpd->name);
>-- 
>1.9.1
>
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Ulf Hansson Jan. 31, 2017, 4:41 p.m. UTC | #3
On 31 January 2017 at 17:17, Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> Hi Ulf,
>
> On Tue, Jan 31, 2017 at 5:01 PM, Ulf Hansson <ulf.hansson@linaro.org> wrote:
>> The earlier comment stated that the dev_warn_once() was going to be printed
>> once per device. Let's fix that, as dev_warn_once() is printed only once,
>> no matter of the device.
>
> While I agree this makes the comment match the code, I think we would serve
> the users better by printing the warning once per PM domain.
> Currently the user cannot know if two or more PM domains cannot be powered
> off due to IRQ safe devices.

Right.

>
> Perhaps a flag can be added to generic_pm_domain.flags to remember
> that the warning has been printed before?

That seems like a reasonable adjustment. Allow me to cook a patch on
top of this one.

Moreover, I was thinking of considering to check for always on domains
and perhaps skip printing this message in such cases. Would that make
sense as well?

Kind regards
Uffe

>
>> Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
>> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
>> ---
>>  drivers/base/power/domain.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
>> index 6b23d82..271e208 100644
>> --- a/drivers/base/power/domain.c
>> +++ b/drivers/base/power/domain.c
>> @@ -130,7 +130,7 @@ static inline bool irq_safe_dev_in_no_sleep_domain(struct device *dev,
>>
>>         ret = pm_runtime_is_irq_safe(dev) && !genpd_is_irq_safe(genpd);
>>
>> -       /* Warn once for each IRQ safe dev in no sleep domain */
>> +       /* Warn once if IRQ safe dev in no sleep domain */
>>         if (ret)
>>                 dev_warn_once(dev, "PM domain %s will not be powered off\n",
>>                                 genpd->name);
>
> Gr{oetje,eeting}s,
>
>                         Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
>
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                 -- Linus Torvalds
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Geert Uytterhoeven Jan. 31, 2017, 5:17 p.m. UTC | #4
Hi Ulf,

On Tue, Jan 31, 2017 at 5:41 PM, Ulf Hansson <ulf.hansson@linaro.org> wrote:
> On 31 January 2017 at 17:17, Geert Uytterhoeven <geert@linux-m68k.org> wrote:
>> On Tue, Jan 31, 2017 at 5:01 PM, Ulf Hansson <ulf.hansson@linaro.org> wrote:
>>> The earlier comment stated that the dev_warn_once() was going to be printed
>>> once per device. Let's fix that, as dev_warn_once() is printed only once,
>>> no matter of the device.
>>
>> While I agree this makes the comment match the code, I think we would serve
>> the users better by printing the warning once per PM domain.
>> Currently the user cannot know if two or more PM domains cannot be powered
>> off due to IRQ safe devices.
>
> Right.
>
>> Perhaps a flag can be added to generic_pm_domain.flags to remember
>> that the warning has been printed before?
>
> That seems like a reasonable adjustment. Allow me to cook a patch on
> top of this one.

Thanks!

> Moreover, I was thinking of considering to check for always on domains
> and perhaps skip printing this message in such cases. Would that make
> sense as well?

That would make sense.

But how would you check that?
By comparing its governor with &pm_domain_always_on_gov?
Note that that is not sufficient, as I think its power_off() callback will still
be called. Only if it fails to power off and returns -EBUSY, it's a real
always-on domain.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
--
To unsubscribe from this list: send the line "unsubscribe linux-pm" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Ulf Hansson Feb. 2, 2017, 9:55 a.m. UTC | #5
On 31 January 2017 at 18:17, Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> Hi Ulf,
>
> On Tue, Jan 31, 2017 at 5:41 PM, Ulf Hansson <ulf.hansson@linaro.org> wrote:
>> On 31 January 2017 at 17:17, Geert Uytterhoeven <geert@linux-m68k.org> wrote:
>>> On Tue, Jan 31, 2017 at 5:01 PM, Ulf Hansson <ulf.hansson@linaro.org> wrote:
>>>> The earlier comment stated that the dev_warn_once() was going to be printed
>>>> once per device. Let's fix that, as dev_warn_once() is printed only once,
>>>> no matter of the device.
>>>
>>> While I agree this makes the comment match the code, I think we would serve
>>> the users better by printing the warning once per PM domain.
>>> Currently the user cannot know if two or more PM domains cannot be powered
>>> off due to IRQ safe devices.
>>
>> Right.
>>
>>> Perhaps a flag can be added to generic_pm_domain.flags to remember
>>> that the warning has been printed before?
>>
>> That seems like a reasonable adjustment. Allow me to cook a patch on
>> top of this one.
>
> Thanks!
>
>> Moreover, I was thinking of considering to check for always on domains
>> and perhaps skip printing this message in such cases. Would that make
>> sense as well?
>
> That would make sense.
>
> But how would you check that?
> By comparing its governor with &pm_domain_always_on_gov?
> Note that that is not sufficient, as I think its power_off() callback will still
> be called. Only if it fails to power off and returns -EBUSY, it's a real
> always-on domain.

Hi Geert,

Correct! At this point, I am looking into how I in general can improve
the code in genpd dealing with always on PM domains.

It seems like the genpd client, shouldn't need to implement the
->power_off|on() callbacks at all, but instead just configure the
genpd at init time as an always on PM domain.

Then that information can be used in genpd at various places, to do
optimizations and likely to avoid printing non-needed errors/warnings.
I keep you posted.

Kind regards
Uffe
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Patch
diff mbox

diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
index 6b23d82..271e208 100644
--- a/drivers/base/power/domain.c
+++ b/drivers/base/power/domain.c
@@ -130,7 +130,7 @@  static inline bool irq_safe_dev_in_no_sleep_domain(struct device *dev,
 
 	ret = pm_runtime_is_irq_safe(dev) && !genpd_is_irq_safe(genpd);
 
-	/* Warn once for each IRQ safe dev in no sleep domain */
+	/* Warn once if IRQ safe dev in no sleep domain */
 	if (ret)
 		dev_warn_once(dev, "PM domain %s will not be powered off\n",
 				genpd->name);