[alsa-devel] [PATCH] hda: STAC927x power down inactive DACs

[Takashi Iwai]

At Wed, 30 Jan 2008 09:14:02 -0500,
Matthew Ranostay wrote:
> 
> On several laptops that have STAC9228 codecs have unused DACs, this powers them down to a D3 state.
> 
> Signed-off-by: Matthew Ranostay <mranostay at embeddedalley.com>

I think they will be eventually powered up again in
hda_set_power_state() in hda_codec.c.  As a temporary solution, we can
have a sort of blacklist in struct hda_codec for always turning the
power off for such widgets.

As a long-term solution, the automatic detection of such widgets would
be nice...


Takashi


> ---
> diff -r 86c8c0a82bb9 pci/hda/patch_sigmatel.c
> --- a/pci/hda/patch_sigmatel.c	Wed Jan 30 11:52:33 2008 +0100
> +++ b/pci/hda/patch_sigmatel.c	Wed Jan 30 08:58:37 2008 -0500
> @@ -288,6 +288,10 @@ static hda_nid_t stac927x_adc_nids[3] = 
>  
>  static hda_nid_t stac927x_mux_nids[3] = {
>          0x15, 0x16, 0x17
> +};
> +
> +static hda_nid_t stac927x_dac_nids[5] = {
> +	0x02, 0x03, 0x04, 0x05, 0x06
>  };
>  
>  static hda_nid_t stac927x_dmux_nids[1] = {
> @@ -3537,7 +3541,7 @@ static int patch_stac927x(struct hda_cod
>  static int patch_stac927x(struct hda_codec *codec)
>  {
>  	struct sigmatel_spec *spec;
> -	int err;
> +	int err, i;
>  
>  	spec  = kzalloc(sizeof(*spec), GFP_KERNEL);
>  	if (spec == NULL)
> @@ -3628,6 +3632,14 @@ static int patch_stac927x(struct hda_cod
>  		stac92xx_free(codec);
>  		return err;
>  	}
> +
> +	/* on some 3-stack systems not all the DACs are used
> + 	 * this powers down ones that aren't used
> + 	 */
> +	for (i = 0; i < ARRAY_SIZE(stac927x_dac_nids); i++)
> +		if (!is_in_dac_nids(spec, stac927x_dac_nids[i]))
> +			snd_hda_codec_write_cache(codec, stac927x_dac_nids[i],
> +				0, AC_VERB_SET_POWER_STATE, AC_PWRST_D3);
>  
>  	codec->patch_ops = stac92xx_patch_ops;
>