ASoC: Actively manage the DC servo for WM8903

Save a little extra power by enabling the DC servo offset correction
for the output channels only when the relevant channels are enabled.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/sound/soc/codecs/wm8903.c b/sound/soc/codecs/wm8903.c
index de0a58507202..0bab5c6bd64a 100644
--- a/sound/soc/codecs/wm8903.c
+++ b/sound/soc/codecs/wm8903.c
@@ -392,14 +392,18 @@ static int wm8903_output_event(struct snd_soc_dapm_widget *w,
         struct snd_soc_codec *codec = w->codec;
         u16 val;
         u16 reg;
+        u16 dcs_reg;
+        u16 dcs_bit;
         int shift;
 
         switch (w->reg) {
         case WM8903_POWER_MANAGEMENT_2:
                 reg = WM8903_ANALOGUE_HP_0;
+                dcs_bit = 0 + w->shift;
                 break;
         case WM8903_POWER_MANAGEMENT_3:
                 reg = WM8903_ANALOGUE_LINEOUT_0;
+                dcs_bit = 2 + w->shift;
                 break;
         default:
                 BUG();
@@ -439,6 +443,11 @@ static int wm8903_output_event(struct snd_soc_dapm_widget *w,
                 val |= (WM8903_OUTPUT_OUT << shift);
                 wm8903_write(codec, reg, val);
 
+                /* Enable the DC servo */
+                dcs_reg = wm8903_read(codec, WM8903_DC_SERVO_0);
+                dcs_reg |= dcs_bit;
+                wm8903_write(codec, WM8903_DC_SERVO_0, dcs_reg);
+
                 /* Remove the short */
                 val |= (WM8903_OUTPUT_SHORT << shift);
                 wm8903_write(codec, reg, val);
@@ -451,6 +460,11 @@ static int wm8903_output_event(struct snd_soc_dapm_widget *w,
                 val &= ~(WM8903_OUTPUT_SHORT << shift);
                 wm8903_write(codec, reg, val);
 
+                /* Disable the DC servo */
+                dcs_reg = wm8903_read(codec, WM8903_DC_SERVO_0);
+                dcs_reg &= ~dcs_bit;
+                wm8903_write(codec, WM8903_DC_SERVO_0, dcs_reg);
+
                 /* Then disable the intermediate and output stages */
                 val &= ~((WM8903_OUTPUT_OUT | WM8903_OUTPUT_INT |
                           WM8903_OUTPUT_IN) << shift);