[alsa-devel] [PATCH RFC 2/3] ASoC: hdmi-codec: add support for bclk_ratio

[Russell King]

Some HDMI codecs need to know the relationship between the I2S bit clock
and the I2S word clock in order to correctly generate the CTS value for
audio clock recovery on the sink.

Add support for this, but there are currently no callers of
snd_soc_dai_set_bclk_ratio(), we provide a default implementation that
uses the sample width to derive the ratio from the 8-bit aligned
sample size.  This reflects the derivation that is in TDA998x, which
we are going to convert to use this new support.

Signed-off-by: Russell King <rmk+kernel at armlinux.org.uk>
---
 include/sound/hdmi-codec.h    |  1 +
 sound/soc/codecs/hdmi-codec.c | 45 +++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 44 insertions(+), 2 deletions(-)

diff --git a/include/sound/hdmi-codec.h b/include/sound/hdmi-codec.h
index 9483c55f871b..0fca69880dc3 100644
--- a/include/sound/hdmi-codec.h
+++ b/include/sound/hdmi-codec.h
@@ -42,6 +42,7 @@ struct hdmi_codec_daifmt {
 	unsigned int frame_clk_inv:1;
 	unsigned int bit_clk_master:1;
 	unsigned int frame_clk_master:1;
+	unsigned int bclk_ratio;
 };
 
 /*
diff --git a/sound/soc/codecs/hdmi-codec.c b/sound/soc/codecs/hdmi-codec.c
index e5b6769b9797..d71a7e5a2231 100644
--- a/sound/soc/codecs/hdmi-codec.c
+++ b/sound/soc/codecs/hdmi-codec.c
@@ -470,6 +470,7 @@ static int hdmi_codec_hw_params(struct snd_pcm_substream *substream,
 				struct snd_soc_dai *dai)
 {
 	struct hdmi_codec_priv *hcp = snd_soc_dai_get_drvdata(dai);
+	struct hdmi_codec_daifmt fmt;
 	struct hdmi_codec_params hp = {
 		.iec = {
 			.status = { 0 },
@@ -520,8 +521,43 @@ static int hdmi_codec_hw_params(struct snd_pcm_substream *substream,
 	hp.sample_rate = params_rate(params);
 	hp.channels = params_channels(params);
 
+	fmt = hcp->daifmt[dai->id];
+
+	/*
+	 * If the .set_bclk_ratio() has not been called, default it
+	 * using the sample width for compatibility for TDA998x.
+	 * Rather than changing this, drivers should arrange to make
+	 * an appropriate call to snd_soc_dai_set_bclk_ratio().
+	 */
+	if (fmt.bclk_ratio == 0) {
+		switch (hp.sample_width) {
+		case 16:
+			fmt.bclk_ratio = 32;
+			break;
+		case 18:
+		case 20:
+		case 24:
+			fmt.bclk_ratio = 48;
+			break;
+		default:
+			fmt.bclk_ratio = 64;
+			break;
+		}
+	}
+
 	return hcp->hcd.ops->hw_params(dai->dev->parent, hcp->hcd.data,
-				       &hcp->daifmt[dai->id], &hp);
+				       &fmt, &hp);
+}
+
+static int hdmi_codec_set_bclk_ratio(struct snd_soc_dai *dai,
+				     unsigned int ratio)
+{
+	struct hdmi_codec_priv *hcp = snd_soc_dai_get_drvdata(dai);
+
+	/* FIXME: some validation here would be good? */
+	hcp->daifmt[dai->id].bclk_ratio = ratio;
+
+	return 0;
 }
 
 static int hdmi_codec_set_fmt(struct snd_soc_dai *dai,
@@ -593,7 +629,11 @@ static int hdmi_codec_set_fmt(struct snd_soc_dai *dai,
 		}
 	}
 
-	hcp->daifmt[dai->id] = cf;
+	hcp->daifmt[dai->id].fmt = cf.fmt;
+	hcp->daifmt[dai->id].bit_clk_inv = cf.bit_clk_inv;
+	hcp->daifmt[dai->id].frame_clk_inv = cf.frame_clk_inv;
+	hcp->daifmt[dai->id].bit_clk_master = cf.bit_clk_master;
+	hcp->daifmt[dai->id].frame_clk_master = cf.frame_clk_master;
 
 	return ret;
 }
@@ -615,6 +655,7 @@ static const struct snd_soc_dai_ops hdmi_dai_ops = {
 	.startup	= hdmi_codec_startup,
 	.shutdown	= hdmi_codec_shutdown,
 	.hw_params	= hdmi_codec_hw_params,
+	.set_bclk_ratio	= hdmi_codec_set_bclk_ratio,
 	.set_fmt	= hdmi_codec_set_fmt,
 	.digital_mute	= hdmi_codec_digital_mute,
 };
-- 
2.7.4