[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>

include/sound/ac97_codec.h

@@ -27,6 +27,7 @@
 
 #include <linux/bitops.h>
 #include <linux/device.h>
+#include <linux/workqueue.h>
 #include "pcm.h"
 #include "control.h"
 #include "info.h"
@@ -140,6 +141,20 @@
 #define AC97_GP_DRSS_1011	0x0000	/* LR(C) 10+11(+12) */
 #define AC97_GP_DRSS_78		0x0400	/* LR 7+8 */
 
+/* powerdown bits */
+#define AC97_PD_ADC_STATUS	0x0001	/* ADC status (RO) */
+#define AC97_PD_DAC_STATUS	0x0002	/* DAC status (RO) */
+#define AC97_PD_MIXER_STATUS	0x0004	/* Analog mixer status (RO) */
+#define AC97_PD_VREF_STATUS	0x0008	/* Vref status (RO) */
+#define AC97_PD_PR0		0x0100	/* Power down PCM ADCs and input MUX */
+#define AC97_PD_PR1		0x0200	/* Power down PCM front DAC */
+#define AC97_PD_PR2		0x0400	/* Power down Mixer (Vref still on) */
+#define AC97_PD_PR3		0x0800	/* Power down Mixer (Vref off) */
+#define AC97_PD_PR4		0x1000	/* Power down AC-Link */
+#define AC97_PD_PR5		0x2000	/* Disable internal clock usage */
+#define AC97_PD_PR6		0x4000	/* Headphone amplifier */
+#define AC97_PD_EAPD		0x8000	/* External Amplifer Power Down (EAPD) */
+
 /* extended audio ID bit defines */
 #define AC97_EI_VRA		0x0001	/* Variable bit rate supported */
 #define AC97_EI_DRA		0x0002	/* Double rate supported */
@@ -359,6 +374,7 @@
 #define AC97_SCAP_INV_EAPD	(1<<7)	/* inverted EAPD */
 #define AC97_SCAP_DETECT_BY_VENDOR (1<<8) /* use vendor registers for read tests */
 #define AC97_SCAP_NO_SPDIF	(1<<9)	/* don't build SPDIF controls */
+#define AC97_SCAP_EAPD_LED	(1<<10)	/* EAPD as mute LED */
 
 /* ac97->flags */
 #define AC97_HAS_PC_BEEP	(1<<0)	/* force PC Speaker usage */
@@ -491,6 +507,12 @@ struct snd_ac97 {
 	/* jack-sharing info */
 	unsigned char indep_surround;
 	unsigned char channel_mode;
+
+#ifdef CONFIG_SND_AC97_POWER_SAVE
+	unsigned int power_up;	/* power states */
+	struct workqueue_struct *power_workq;
+	struct work_struct power_work;
+#endif
 	struct device dev;
 };
 
@@ -532,6 +554,15 @@ unsigned short snd_ac97_read(struct snd_ac97 *ac97, unsigned short reg);
 void snd_ac97_write_cache(struct snd_ac97 *ac97, unsigned short reg, unsigned short value);
 int snd_ac97_update(struct snd_ac97 *ac97, unsigned short reg, unsigned short value);
 int snd_ac97_update_bits(struct snd_ac97 *ac97, unsigned short reg, unsigned short mask, unsigned short value);
+#ifdef CONFIG_SND_AC97_POWER_SAVE
+int snd_ac97_update_power(struct snd_ac97 *ac97, int reg, int powerup);
+#else
+static inline int snd_ac97_update_power(struct snd_ac97 *ac97, int reg,
+					int powerup)
+{
+	return 0;
+}
+#endif
 #ifdef CONFIG_PM
 void snd_ac97_suspend(struct snd_ac97 *ac97);
 void snd_ac97_resume(struct snd_ac97 *ac97);
@@ -583,6 +614,7 @@ struct ac97_pcm {
 		     copy_flag: 1,	   /* lowlevel driver must fill all entries */
 		     spdif: 1;		   /* spdif pcm */
 	unsigned short aslots;		   /* active slots */
+	unsigned short cur_dbl;		   /* current double-rate state */
 	unsigned int rates;		   /* available rates */
 	struct {
 		unsigned short slots;	   /* driver input: requested AC97 slot numbers */

sound/drivers/Kconfig

@@ -100,4 +100,17 @@ config SND_MPU401
 	  To compile this driver as a module, choose M here: the module
 	  will be called snd-mpu401.
 
+config SND_AC97_POWER_SAVE
+	bool "AC97 Power-Saving Mode"
+	depends on SND_AC97_CODEC && EXPERIMENTAL
+	default n
+	help
+	  Say Y here to enable the aggressive power-saving support of
+	  AC97 codecs.  In this mode, the power-mode is dynamically
+	  controlled at each open/close.
+
+	  The mode is activated by passing power_save=1 option to
+	  snd-ac97-codec driver.  You can toggle it dynamically over
+	  sysfs, too.
+
 endmenu

sound/pci/ac97/ac97_pcm.c

@@ -269,6 +269,7 @@ int snd_ac97_set_rate(struct snd_ac97 *ac97, int reg, unsigned int rate)
 			return -EINVAL;
 	}
 
+	snd_ac97_update_power(ac97, reg, 1);
 	switch (reg) {
 	case AC97_PCM_MIC_ADC_RATE:
 		if ((ac97->regs[AC97_EXTENDED_STATUS] & AC97_EA_VRM) == 0)	/* MIC VRA */
@@ -606,6 +607,7 @@ int snd_ac97_pcm_open(struct ac97_pcm *pcm, unsigned int rate,
 			goto error;
 		}
 	}
+	pcm->cur_dbl = r;
 	spin_unlock_irq(&pcm->bus->bus_lock);
 	for (i = 3; i < 12; i++) {
 		if (!(slots & (1 << i)))
@@ -651,6 +653,21 @@ int snd_ac97_pcm_close(struct ac97_pcm *pcm)
 	unsigned short slots = pcm->aslots;
 	int i, cidx;
 
+#ifdef CONFIG_SND_AC97_POWER_SAVE
+	int r = pcm->cur_dbl;
+	for (i = 3; i < 12; i++) {
+		if (!(slots & (1 << i)))
+			continue;
+		for (cidx = 0; cidx < 4; cidx++) {
+			if (pcm->r[r].rslots[cidx] & (1 << i)) {
+				int reg = get_slot_reg(pcm, cidx, i, r);
+				snd_ac97_update_power(pcm->r[r].codec[cidx],
+						      reg, 0);
+			}
+		}
+	}
+#endif
+
 	bus = pcm->bus;
 	spin_lock_irq(&pcm->bus->bus_lock);
 	for (i = 3; i < 12; i++) {
@@ -660,6 +677,7 @@ int snd_ac97_pcm_close(struct ac97_pcm *pcm)
 			bus->used_slots[pcm->stream][cidx] &= ~(1 << i);
 	}
 	pcm->aslots = 0;
+	pcm->cur_dbl = 0;
 	spin_unlock_irq(&pcm->bus->bus_lock);
 	return 0;
 }

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

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;
 }