[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, 13 insertions, 1 deletions

diff --git a/sound/pci/intel8x0.c b/sound/pci/intel8x0.c
index 6874263f1681..72dbaedcbdf5 100644
--- a/sound/pci/intel8x0.c
+++ b/sound/pci/intel8x0.c
@@ -2251,6 +2251,16 @@ static int snd_intel8x0_ich_chip_init(struct intel8x0 *chip, int probing)
         /* ACLink on, 2 channels */
         cnt = igetdword(chip, ICHREG(GLOB_CNT));
         cnt &= ~(ICH_ACLINK | ICH_PCM_246_MASK);
+#ifdef CONFIG_SND_AC97_POWER_SAVE
+        /* do cold reset - the full ac97 powerdown may leave the controller
+         * in a warm state but actually it cannot communicate with the codec.
+         */
+        iputdword(chip, ICHREG(GLOB_CNT), cnt & ~ICH_AC97COLD);
+        cnt = igetdword(chip, ICHREG(GLOB_CNT));
+        udelay(10);
+        iputdword(chip, ICHREG(GLOB_CNT), cnt | ICH_AC97COLD);
+        msleep(1);
+#else
         /* finish cold or do warm reset */
         cnt |= (cnt & ICH_AC97COLD) == 0 ? ICH_AC97COLD : ICH_AC97WARM;
         iputdword(chip, ICHREG(GLOB_CNT), cnt);
@@ -2265,6 +2275,7 @@ static int snd_intel8x0_ich_chip_init(struct intel8x0 *chip, int probing)
         return -EIO;
 
       __ok:
+#endif
         if (probing) {
                 /* wait for any codec ready status.
                  * Once it becomes ready it should remain ready
@@ -2485,7 +2496,7 @@ static int intel8x0_resume(struct pci_dev *pci)
                     card->shortname, chip);
         chip->irq = pci->irq;
         synchronize_irq(chip->irq);
-        snd_intel8x0_chip_init(chip, 1);
+        snd_intel8x0_chip_init(chip, 0);
 
         /* re-initialize mixer stuff */
         if (chip->device_type == DEVICE_INTEL_ICH4) {
@@ -2615,6 +2626,7 @@ static void __devinit intel8x0_measure_ac97_clock(struct intel8x0 *chip)
                 /* not 48000Hz, tuning the clock.. */
                 chip->ac97_bus->clock = (chip->ac97_bus->clock * 48000) / pos;
         printk(KERN_INFO "intel8x0: clocking to %d\n", chip->ac97_bus->clock);
+        snd_ac97_update_power(chip->ac97[0], AC97_PCM_FRONT_DAC_RATE, 0);
 }
 
 #ifdef CONFIG_PROC_FS