Re: [PATCH 1/1] PM / Runtime: let rpm_resume fail if rpm disabled and device suspended.

Alan Stern
2014-06-14T14:32:11Z

On Sat, 14 Jun 2014, Allen Yu wrote:

> dev->power.is_suspended is set after core suspends device during system suspend.
> This flag mostly means device is not operational (all I/O been quiesced, no more
> data read or write acceptible, etc.), hence it's dangerous to access hardware if
> device is suspended even though runtime PM status is RPM_ACTIVE.
>
> In turn, we should allow device to be accessed in case device is *not* suspended
> and runtime PM status is RPM_ACTIVE, even if runtime PM disabled. This corner case
> can happen to a device in a generic PM domain if the domain is not powered off while
> preparing for a system-wide power transition.

I don't understand. Even if the PM domain isn't powered off, the
device's is_suspended flag will still be set by __device_suspend().

> In this case, runtime PM status will
> be set to RPM_ACTIVE and then runtime PM is disabled. After that, device driver may
> call pm_runtime_get_sync() and rpm_resume() should return 1, because the device is
> still active as long as not been suspended.

Isn't that what the existing code does already? Your patch seems to
change it so that it _doesn't_ behave the way you want.

> Signed-off-by: Allen Yu <alleny@nvidia.com>
> ---
> drivers/base/power/runtime.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
> index 67c7938..39885f1 100644
> --- a/drivers/base/power/runtime.c
> +++ b/drivers/base/power/runtime.c
> @@ -608,7 +608,7 @@ 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
> + else if (dev->power.disable_depth == 1 && !dev->power.is_suspended
> && dev->power.runtime_status == RPM_ACTIVE)
> retval = 1;

Alan Stern