[alsa-devel] [PATCH] ALSA: hda - Don't power up when not powered down.

[Takashi Iwai]

At Thu, 21 Jun 2012 21:51:22 -0700,
Dylan Reid wrote:
> 
> After cancel_delayed_work_sync returns, the power down work either never
> started (power_on == 1) or finished (power_on == 0).  In the former case
> there is no need to power up again.
> 
> Signed-off-by: Dylan Reid <dgreid at chromium.org>

There is still a small window between cancel_delayed_work_sync() and
the spinlock, so the power down might happen between them, in theory.
(And due to the obvious reason, cancel_delayed_work_sync() can't be in
 spinlock :)


thanks,

Takashi

> ---
>  sound/pci/hda/hda_codec.c |    7 +++++++
>  1 files changed, 7 insertions(+), 0 deletions(-)
> 
> diff --git a/sound/pci/hda/hda_codec.c b/sound/pci/hda/hda_codec.c
> index 604699c..045b5e7 100644
> --- a/sound/pci/hda/hda_codec.c
> +++ b/sound/pci/hda/hda_codec.c
> @@ -4444,6 +4444,13 @@ static void __snd_hda_power_up(struct hda_codec *codec, bool wait_power_down)
>  	cancel_delayed_work_sync(&codec->power_work);
>  
>  	spin_lock(&codec->power_lock);
> +	/* If the power down delayed work was cancelled above before starting,
> +	 * then there is no need to go through power up here.
> +	 */
> +	if (codec->power_on) {
> +		spin_unlock(&codec->power_lock);
> +		return;
> +	}
>  	trace_hda_power_up(codec);
>  	snd_hda_update_power_acct(codec);
>  	codec->power_on = 1;
> -- 
> 1.7.9.rc0
>