From: Alan Stern <stern@rowland.harvard.edu>
To: Ulf Hansson <ulf.hansson@linaro.org>
Cc: "Rafael J . Wysocki" <rjw@rjwysocki.net>,
"Rafael J . Wysocki" <rafael@kernel.org>,
linux-pm@vger.kernel.org, Kevin Hilman <khilman@kernel.org>,
Maulik Shah <mkshah@codeaurora.org>,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] PM: runtime: Allow rpm_resume() to succeed when runtime PM is disabled
Date: Tue, 26 Oct 2021 22:02:35 -0400 [thread overview]
Message-ID: <20211027020235.GA1306582@rowland.harvard.edu> (raw)
In-Reply-To: <20211026222626.39222-1-ulf.hansson@linaro.org>
On Wed, Oct 27, 2021 at 12:26:26AM +0200, Ulf Hansson wrote:
> During system suspend, the PM core sets dev->power.is_suspended for the
> device that is being suspended. This flag is also being used in
> rpm_resume(), to allow it to succeed by returning 1, assuming that runtime
> PM has been disabled and the runtime PM status is RPM_ACTIVE, for the
> device.
>
> To make this behaviour a bit more useful, let's drop the check for the
> dev->power.is_suspended flag in rpm_resume(), as it doesn't really need to
> be limited to this anyway.
>
> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
> ---
> drivers/base/power/runtime.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
> index ec94049442b9..fadc278e3a66 100644
> --- a/drivers/base/power/runtime.c
> +++ b/drivers/base/power/runtime.c
> @@ -742,8 +742,8 @@ static int rpm_resume(struct device *dev, int rpmflags)
> repeat:
> if (dev->power.runtime_error)
> retval = -EINVAL;
> - else if (dev->power.disable_depth == 1 && dev->power.is_suspended
> - && dev->power.runtime_status == RPM_ACTIVE)
> + else if (dev->power.disable_depth > 0 &&
> + dev->power.runtime_status == RPM_ACTIVE)
IIRC there was a good reason why the original code checked for
disable_depth == 1 rather than > 0. But I don't remember exactly what
the reason was. Maybe it had something to do with the fact that during
a system sleep __device_suspend_late calls __pm_runtime_disable, and the
code was checking that there were no other disables in effect. This is
related to the documented behavior of rpm_resume (it's supposed to fail
with -EACCES if the device is disabled for runtime PM, no matter what
power state the device is in).
That probably is also the explanation for why dev->power.is_suspended
gets checked: It's how the code tells whether a system sleep is in
progress.
So overall, I suspect this change should not be made. But some other
improvement (like a nice comment) might be in order.
Alan Stern
WARNING: multiple messages have this Message-ID (diff)
From: Alan Stern <stern@rowland.harvard.edu>
To: Ulf Hansson <ulf.hansson@linaro.org>
Cc: "Rafael J . Wysocki" <rjw@rjwysocki.net>,
"Rafael J . Wysocki" <rafael@kernel.org>,
linux-pm@vger.kernel.org, Kevin Hilman <khilman@kernel.org>,
Maulik Shah <mkshah@codeaurora.org>,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] PM: runtime: Allow rpm_resume() to succeed when runtime PM is disabled
Date: Tue, 26 Oct 2021 22:02:35 -0400 [thread overview]
Message-ID: <20211027020235.GA1306582@rowland.harvard.edu> (raw)
In-Reply-To: <20211026222626.39222-1-ulf.hansson@linaro.org>
On Wed, Oct 27, 2021 at 12:26:26AM +0200, Ulf Hansson wrote:
> During system suspend, the PM core sets dev->power.is_suspended for the
> device that is being suspended. This flag is also being used in
> rpm_resume(), to allow it to succeed by returning 1, assuming that runtime
> PM has been disabled and the runtime PM status is RPM_ACTIVE, for the
> device.
>
> To make this behaviour a bit more useful, let's drop the check for the
> dev->power.is_suspended flag in rpm_resume(), as it doesn't really need to
> be limited to this anyway.
>
> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
> ---
> drivers/base/power/runtime.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
> index ec94049442b9..fadc278e3a66 100644
> --- a/drivers/base/power/runtime.c
> +++ b/drivers/base/power/runtime.c
> @@ -742,8 +742,8 @@ static int rpm_resume(struct device *dev, int rpmflags)
> repeat:
> if (dev->power.runtime_error)
> retval = -EINVAL;
> - else if (dev->power.disable_depth == 1 && dev->power.is_suspended
> - && dev->power.runtime_status == RPM_ACTIVE)
> + else if (dev->power.disable_depth > 0 &&
> + dev->power.runtime_status == RPM_ACTIVE)
IIRC there was a good reason why the original code checked for
disable_depth == 1 rather than > 0. But I don't remember exactly what
the reason was. Maybe it had something to do with the fact that during
a system sleep __device_suspend_late calls __pm_runtime_disable, and the
code was checking that there were no other disables in effect. This is
related to the documented behavior of rpm_resume (it's supposed to fail
with -EACCES if the device is disabled for runtime PM, no matter what
power state the device is in).
That probably is also the explanation for why dev->power.is_suspended
gets checked: It's how the code tells whether a system sleep is in
progress.
So overall, I suspect this change should not be made. But some other
improvement (like a nice comment) might be in order.
Alan Stern
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2021-10-27 2:02 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-26 22:26 [PATCH] PM: runtime: Allow rpm_resume() to succeed when runtime PM is disabled Ulf Hansson
2021-10-26 22:26 ` Ulf Hansson
2021-10-27 2:02 ` Alan Stern [this message]
2021-10-27 2:02 ` Alan Stern
2021-10-27 10:55 ` Ulf Hansson
2021-10-27 10:55 ` Ulf Hansson
2021-10-27 14:33 ` Alan Stern
2021-10-27 14:33 ` Alan Stern
2021-10-28 22:20 ` Ulf Hansson
2021-10-28 22:20 ` Ulf Hansson
2021-10-29 18:26 ` Rafael J. Wysocki
2021-10-29 18:26 ` Rafael J. Wysocki
2021-11-01 9:27 ` Ulf Hansson
2021-11-01 9:27 ` Ulf Hansson
2021-11-01 14:41 ` Grygorii Strashko
2021-11-01 14:41 ` Grygorii Strashko
2021-11-05 16:03 ` Ulf Hansson
2021-11-05 16:03 ` Ulf Hansson
2021-11-26 12:19 ` Ulf Hansson
2021-11-26 12:19 ` Ulf Hansson
2021-11-26 13:30 ` Rafael J. Wysocki
2021-11-26 13:30 ` Rafael J. Wysocki
2021-11-26 13:46 ` Ulf Hansson
2021-11-26 13:46 ` Ulf Hansson
2021-11-26 17:58 ` Rafael J. Wysocki
2021-11-26 17:58 ` Rafael J. Wysocki
2021-11-26 18:29 ` Rafael J. Wysocki
2021-11-26 18:29 ` Rafael J. Wysocki
2021-11-30 11:57 ` Ulf Hansson
2021-11-30 11:57 ` Ulf Hansson
2021-11-30 13:01 ` Rafael J. Wysocki
2021-11-30 13:01 ` Rafael J. Wysocki
2021-11-30 16:41 ` Ulf Hansson
2021-11-30 16:41 ` Ulf Hansson
2021-11-30 17:26 ` Rafael J. Wysocki
2021-11-30 17:26 ` Rafael J. Wysocki
2021-12-01 9:02 ` Ulf Hansson
2021-12-01 9:02 ` Ulf Hansson
2021-12-01 13:49 ` Rafael J. Wysocki
2021-12-01 13:49 ` Rafael J. Wysocki
2021-12-01 15:22 ` Ulf Hansson
2021-12-01 15:22 ` Ulf Hansson
2021-12-01 17:44 ` Rafael J. Wysocki
2021-12-01 17:44 ` Rafael J. Wysocki
2021-12-01 20:11 ` Rafael J. Wysocki
2021-12-01 20:11 ` Rafael J. Wysocki
2021-12-02 11:28 ` Ulf Hansson
2021-12-02 11:28 ` Ulf Hansson
2021-12-02 16:18 ` Rafael J. Wysocki
2021-12-02 16:18 ` Rafael J. Wysocki
2021-12-02 16:50 ` Alan Stern
2021-12-02 16:50 ` Alan Stern
2021-12-02 18:01 ` Rafael J. Wysocki
2021-12-02 18:01 ` Rafael J. Wysocki
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