linux-kernel - Re: [PATCH] PM / Runtime: honor device autosuspend in pm_generic_runtime

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Date:	Mon, 13 May 2013 13:50:18 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:	linux-pm@...r.kernel.org, Pavel Machek <pavel@....cz>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Len Brown <len.brown@...el.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PM / Runtime: honor device autosuspend in pm_generic_runtime_idle()

On Monday, May 13, 2013 02:05:27 PM Mika Westerberg wrote:
> If the device is using autosuspend we should honor that and call
> pm_runtime_autosuspend() instead of pm_runtime_suspend(). Failing to do so
> causes the device to be suspended immediately even though it expects to be
> suspended only when the autosuspend delay is expired.
> 
> Signed-off-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
> ---
>  drivers/base/power/generic_ops.c |    5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/base/power/generic_ops.c b/drivers/base/power/generic_ops.c
> index bfd898b..19786ca 100644
> --- a/drivers/base/power/generic_ops.c
> +++ b/drivers/base/power/generic_ops.c
> @@ -29,7 +29,10 @@ int pm_generic_runtime_idle(struct device *dev)
>  			return ret;
>  	}
>  
> -	pm_runtime_suspend(dev);
> +	if (dev->power.use_autosuspend)
> +		pm_runtime_autosuspend(dev);
> +	else
> +		pm_runtime_suspend(dev);
>  	return 0;

First of all, this is racy (power.use_autosuspend shoud be accessed under
power.lock).

Second, this is not the only place we'd need to make this change (the analogous
function for PCI is one example, but there may be others).

Finally, I'm not sure how to address this problem in general.  It may be better
to simply modify rpm_idle() and remove pm_generic_runtime_idle() etc. entirely.

I'll have a look at that, thanks for pointing out the problem.

Rafael


>  }
>  EXPORT_SYMBOL_GPL(pm_generic_runtime_idle);
> 
-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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