fiiom3k: power down amp before switching DAC power modes

As detailed in the <Low Power Mode> section of the AK4376A
datasheet, the amp should be powered down before switching
power modes (or to a sample rate <= 12 KHz).

Change-Id: I3ab0a21c78a3ad2bb418b64c916f7dbe2a843efa

1 files changed, 19 insertions, 1 deletions

diff --git a/firmware/drivers/audio/ak4376.c b/firmware/drivers/audio/ak4376.c
index 2e772ace84..8d2b9f44f3 100644
--- a/firmware/drivers/audio/ak4376.c
+++ b/firmware/drivers/audio/ak4376.c
@@ -245,8 +245,26 @@ void ak4376_set_freqmode(int fsel, int mult, int power_mode)
     if(power_mode == SOUND_LOW_POWER || hw_freq_sampr[fsel] <= SAMPR_12)
         mode_ctrl |= 0x40;
 
+    /* Handle the LPMODE bit */
+    int pwr3 = power_mode == SOUND_LOW_POWER ? 0x11 : 0x01;
+
+    /* The datasheet says the HP amp must be powered down before changing
+     * the operating mode of the DAC or HP amp. I'm assuming this means
+     * the amp must be shut down when changing DSMLP or LPMODE. */
+    int cur_mode_ctrl = ak4376_read(AK4376_REG_MODE_CTRL);
+    int cur_pwr3 = ak4376_read(AK4376_REG_PWR3);
+    bool disable_amp = mode_ctrl != cur_mode_ctrl || pwr3 != cur_pwr3;
+
     /* Program the new settings */
+    if(disable_amp)
+        ak4376_write(AK4376_REG_PWR4, 0x00);
+
     ak4376_write(AK4376_REG_CLOCK_MODE, clock_mode);
     ak4376_write(AK4376_REG_MODE_CTRL, mode_ctrl);
-    ak4376_write(AK4376_REG_PWR3, power_mode == SOUND_LOW_POWER ? 0x11 : 0x01);
+    ak4376_write(AK4376_REG_PWR3, pwr3);
+
+    if(disable_amp) {
+        ak4376_write(AK4376_REG_PWR4, 0x03);
+        mdelay(26);
+    }
 }