[ALSA] Add experimental support of aggressive AC97 power-saving mode

Added CONFIG_SND_AC97_POWER_SAVE kernel config to enable the support
of aggressive AC97 power-saving mode.  In this mode, the AC97
powerdown register bits are dynamically controlled at each open/close
of PCM streams.
The mode is activated via power_save option for snd-ac97-codec
driver.  As default it's off.  It can be turned on/off on the fly
via sysfs, too.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>

1 files changed, 12 insertions, 1 deletions

diff --git a/sound/pci/via82xx.c b/sound/pci/via82xx.c
index 08da9234efb3..2c23a665c3e3 100644
--- a/sound/pci/via82xx.c
+++ b/sound/pci/via82xx.c
@@ -1277,7 +1277,18 @@ static int snd_via82xx_pcm_close(struct snd_pcm_substream *substream)
         if (! ratep->used)
                 ratep->rate = 0;
         spin_unlock_irq(&ratep->lock);
-
+        if (! ratep->rate) {
+                if (! viadev->direction) {
+                        snd_ac97_update_power(chip->ac97,
+                                              AC97_PCM_FRONT_DAC_RATE, 0);
+                        snd_ac97_update_power(chip->ac97,
+                                              AC97_PCM_SURR_DAC_RATE, 0);
+                        snd_ac97_update_power(chip->ac97,
+                                              AC97_PCM_LFE_DAC_RATE, 0);
+                } else
+                        snd_ac97_update_power(chip->ac97,
+                                              AC97_PCM_LR_ADC_RATE, 0);
+        }
         viadev->substream = NULL;
         return 0;
 }