ALSA: oxygen: fix distorted output on AK4396-based cards

When changing the sample rate, the CMI8788's master clock output becomes
unstable for a short time.  The AK4396 needs the master clock to do SPI
writes, so writing to an AK4396 control register directly after a sample
rate change will garble the value.  In our case, this leads to the DACs
being misconfigured to I2S sample format, which results in a wrong
output level and horrible distortions on samples louder than -6 dB.

To fix this, we need to wait until the new master clock signal has
become stable before doing SPI writes.
Signed-off-by: NClemens Ladisch <clemens@ladisch.de>
Signed-off-by: NTakashi Iwai <tiwai@suse.de>

sound/pci/oxygen/hifier.c

@@ -17,6 +17,7 @@
  *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
  */
 
+#include <linux/delay.h>
 #include <linux/pci.h>
 #include <sound/control.h>
 #include <sound/core.h>
@@ -107,6 +108,9 @@ static void set_ak4396_params(struct oxygen *chip,
 	else
 		value |= AK4396_DFS_QUAD;
 	data->ak4396_ctl2 = value;
+
+	msleep(1); /* wait for the new MCLK to become stable */
+
 	ak4396_write(chip, AK4396_CONTROL_1, AK4396_DIF_24_MSB);
 	ak4396_write(chip, AK4396_CONTROL_2, value);
 	ak4396_write(chip, AK4396_CONTROL_1, AK4396_DIF_24_MSB | AK4396_RSTN);

sound/pci/oxygen/oxygen.c

@@ -28,6 +28,7 @@
  * GPIO 1 -> DFS1 of AK5385
  */
 
+#include <linux/delay.h>
 #include <linux/mutex.h>
 #include <linux/pci.h>
 #include <sound/ac97_codec.h>
@@ -213,6 +214,9 @@ static void set_ak4396_params(struct oxygen *chip,
 	else
 		value |= AK4396_DFS_QUAD;
 	data->ak4396_ctl2 = value;
+
+	msleep(1); /* wait for the new MCLK to become stable */
+
 	for (i = 0; i < 4; ++i) {
 		ak4396_write(chip, i,
 			     AK4396_CONTROL_1, AK4396_DIF_24_MSB);