[alsa-devel] [PATCH v2] ASoC: wm8741: Allow master clock switching

[Sergej Sawazki]

The set of supported sample rates depends on the master clock supplied
to the codec. Allow the machine driver to set the required master clock
in hw_params().

Signed-off-by: Sergej Sawazki <ce3a at gmx.de>
---

Charles, Mark,
thanks for your comments.

This patch has been tested on a board with two master clocks, 22.5792MHz
(for 44.1kHz, 88.2kHz, ...) and 24.576MHz (for 48kHz, 96kHz, ...).

Changes since v1 (Suggested by Charles Keepax):
 - Do not entirely delete the startup() method, just don't set any constraints 
   if there is no SYSCLK configured.
 - Clear the SYSCLK in set_dai_sysclk() if freq is 0.

Many thanks for your time and effort,
Sergej

 sound/soc/codecs/wm8741.c | 61 ++++++++++++++++++++---------------------------
 1 file changed, 26 insertions(+), 35 deletions(-)

diff --git a/sound/soc/codecs/wm8741.c b/sound/soc/codecs/wm8741.c
index 09ff01f..b346237 100644
--- a/sound/soc/codecs/wm8741.c
+++ b/sound/soc/codecs/wm8741.c
@@ -125,18 +125,6 @@ static const struct snd_soc_dapm_route wm8741_dapm_routes[] = {
 	{ "VOUTRN", NULL, "DACR" },
 };
 
-static struct {
-	int value;
-	int ratio;
-} lrclk_ratios[WM8741_NUM_RATES] = {
-	{ 1, 128 },
-	{ 2, 192 },
-	{ 3, 256 },
-	{ 4, 384 },
-	{ 5, 512 },
-	{ 6, 768 },
-};
-
 static const unsigned int rates_11289[] = {
 	44100, 88200,
 };
@@ -209,25 +197,16 @@ static const struct snd_pcm_hw_constraint_list constraints_36864 = {
 	.list	= rates_36864,
 };
 
-
 static int wm8741_startup(struct snd_pcm_substream *substream,
 			  struct snd_soc_dai *dai)
 {
 	struct snd_soc_codec *codec = dai->codec;
 	struct wm8741_priv *wm8741 = snd_soc_codec_get_drvdata(codec);
 
-	/* The set of sample rates that can be supported depends on the
-	 * MCLK supplied to the CODEC - enforce this.
-	 */
-	if (!wm8741->sysclk) {
-		dev_err(codec->dev,
-			"No MCLK configured, call set_sysclk() on init\n");
-		return -EINVAL;
-	}
-
-	snd_pcm_hw_constraint_list(substream->runtime, 0,
-				   SNDRV_PCM_HW_PARAM_RATE,
-				   wm8741->sysclk_constraints);
+	if (wm8741->sysclk)
+		snd_pcm_hw_constraint_list(substream->runtime, 0,
+				SNDRV_PCM_HW_PARAM_RATE,
+				wm8741->sysclk_constraints);
 
 	return 0;
 }
@@ -241,17 +220,24 @@ static int wm8741_hw_params(struct snd_pcm_substream *substream,
 	u16 iface = snd_soc_read(codec, WM8741_FORMAT_CONTROL) & 0x1FC;
 	int i;
 
-	/* Find a supported LRCLK ratio */
-	for (i = 0; i < ARRAY_SIZE(lrclk_ratios); i++) {
-		if (wm8741->sysclk / params_rate(params) ==
-		    lrclk_ratios[i].ratio)
+	/* The set of sample rates that can be supported depends on the
+	 * MCLK supplied to the CODEC - enforce this.
+	 */
+	if (!wm8741->sysclk) {
+		dev_err(codec->dev,
+			"No MCLK configured, call set_sysclk() on init or in hw_params\n");
+		return -EINVAL;
+	}
+
+	/* Find a supported LRCLK rate */
+	for (i = 0; i < wm8741->sysclk_constraints->count; i++) {
+		if (wm8741->sysclk_constraints->list[i] == params_rate(params))
 			break;
 	}
 
-	/* Should never happen, should be handled by constraints */
-	if (i == ARRAY_SIZE(lrclk_ratios)) {
-		dev_err(codec->dev, "MCLK/fs ratio %d unsupported\n",
-			wm8741->sysclk / params_rate(params));
+	if (i == wm8741->sysclk_constraints->count) {
+		dev_err(codec->dev, "LRCLK %d unsupported with MCLK %d\n",
+			params_rate(params), wm8741->sysclk);
 		return -EINVAL;
 	}
 
@@ -274,8 +260,8 @@ static int wm8741_hw_params(struct snd_pcm_substream *substream,
 		return -EINVAL;
 	}
 
-	dev_dbg(codec->dev, "wm8741_hw_params:    bit size param = %d",
-		params_width(params));
+	dev_dbg(codec->dev, "wm8741_hw_params:    bit size param = %d, rate param = %d",
+		params_width(params), params_rate(params));
 
 	snd_soc_write(codec, WM8741_FORMAT_CONTROL, iface);
 	return 0;
@@ -290,6 +276,11 @@ static int wm8741_set_dai_sysclk(struct snd_soc_dai *codec_dai,
 	dev_dbg(codec->dev, "wm8741_set_dai_sysclk info: freq=%dHz\n", freq);
 
 	switch (freq) {
+	case 0:
+		wm8741->sysclk_constraints = NULL;
+		wm8741->sysclk = freq;
+		return 0;
+
 	case 11289600:
 		wm8741->sysclk_constraints = &constraints_11289;
 		wm8741->sysclk = freq;
-- 
1.9.1