[alsa-devel] [PATCH V2] ALSA: hda - power setting error check

[Fengguang Wu]

Xingchao,

On Thu, Jun 07, 2012 at 06:21:30PM +0800, Wang Xingchao wrote:
> codec may reject power state transition requests(reporting PS-ERROR set),
> in that case we re-issue a power state setting and check error bit again.

Is this patch based on real errors observed? And tested to fix the issue?

> Signed-off-by: Wang Xingchao <xingchao.wang at intel.com>
> ---
>  sound/pci/hda/hda_codec.c |   17 ++++++++++++++---
>  1 file changed, 14 insertions(+), 3 deletions(-)
> 
> diff --git a/sound/pci/hda/hda_codec.c b/sound/pci/hda/hda_codec.c
> index d0ca370..a93c7ca 100644
> --- a/sound/pci/hda/hda_codec.c
> +++ b/sound/pci/hda/hda_codec.c
> @@ -3526,6 +3526,7 @@ static bool snd_hda_codec_get_supported_ps(struct hda_codec *codec, hda_nid_t fg
>  static void hda_set_power_state(struct hda_codec *codec, hda_nid_t fg,
>  				unsigned int power_state)
>  {
> +	int state, count = 0;

nit pick: break that into two lines?

state should be unsigned int.

>  	if (codec->patch_ops.set_power_state) {
>  		codec->patch_ops.set_power_state(codec, fg, power_state);
>  		return;
> @@ -3537,9 +3538,19 @@ static void hda_set_power_state(struct hda_codec *codec, hda_nid_t fg,
>  		bool epss = snd_hda_codec_get_supported_ps(codec, fg, AC_PWRST_EPSS);
>  		msleep(epss? 10:100);
>  	}
> -	snd_hda_codec_read(codec, fg, 0, AC_VERB_SET_POWER_STATE,
> -			    power_state);
> -	snd_hda_codec_set_power_to_all(codec, fg, power_state, true);
> +
> +	/* repeat power states setting at most 10 times*/
> +	while (count++ > 10) {

< 10?

for(;;) looks slightly better, by putting the initialization together
with test and increase.

> +		snd_hda_codec_read(codec, fg, 0, AC_VERB_SET_POWER_STATE,
> +				    power_state);
> +		snd_hda_codec_set_power_to_all(codec, fg, power_state, true);
> +		state = snd_hda_codec_read(codec, fg, 0,
> +					   AC_VERB_GET_POWER_STATE, 0);
> +		if (!(state & AC_PWRST_ERROR))
> +			break;

Do you have any clue the condition of success? For example, is it time
based (the codec takes some time to respond) or retry count based?

> +	}
> +	if (count > 10)
> +		snd_printk(KERN_WARNING "Power states transition reject!\n");

Power state transition rejected

Hmm, if some codec always rejects it, the user may get lots of these
warnings..

Thanks,
Fengguang