ASoC: wm8994: Support constraining the maximum number of channels clocked

Some systems use the audio CODEC to clock a DAI with multiple data lines
in parallel, meaning that bit clocks are only required for a smaller number
of channels than data is sent for. In some cases providing the extra bit
clocks can take the other devices on the audio bus out of spec.

Support such systems by allowing a maximum number of channels to be
specified.

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

1 files changed, 11 insertions, 2 deletions

diff --git a/sound/soc/codecs/wm8994.c b/sound/soc/codecs/wm8994.c
index c9bd445c4976..318ea64b9800 100644
--- a/sound/soc/codecs/wm8994.c
+++ b/sound/soc/codecs/wm8994.c
@@ -2656,6 +2656,8 @@ static int wm8994_hw_params(struct snd_pcm_substream *substream,
 {
         struct snd_soc_codec *codec = dai->codec;
         struct wm8994_priv *wm8994 = snd_soc_codec_get_drvdata(codec);
+        struct wm8994 *control = wm8994->wm8994;
+        struct wm8994_pdata *pdata = &control->pdata;
         int aif1_reg;
         int aif2_reg;
         int bclk_reg;
@@ -2723,7 +2725,14 @@ static int wm8994_hw_params(struct snd_pcm_substream *substream,
         }
 
         wm8994->channels[id] = params_channels(params);
-        switch (params_channels(params)) {
+        if (pdata->max_channels_clocked[id] &&
+            wm8994->channels[id] > pdata->max_channels_clocked[id]) {
+                dev_dbg(dai->dev, "Constraining channels to %d from %d\n",
+                        pdata->max_channels_clocked[id], wm8994->channels[id]);
+                wm8994->channels[id] = pdata->max_channels_clocked[id];
+        }
+
+        switch (wm8994->channels[id]) {
         case 1:
         case 2:
                 bclk_rate *= 2;
@@ -2745,7 +2754,7 @@ static int wm8994_hw_params(struct snd_pcm_substream *substream,
         dev_dbg(dai->dev, "AIF%dCLK is %dHz, target BCLK %dHz\n",
                 dai->id, wm8994->aifclk[id], bclk_rate);
 
-        if (params_channels(params) == 1 &&
+        if (wm8994->channels[id] == 1 &&
             (snd_soc_read(codec, aif1_reg) & 0x18) == 0x18)
                 aif2 |= WM8994_AIF1_MONO;