[RFC PATCH 4/4] ASoC: fsl_ssi: constrain bclk_ratio in i2s master mode

[Sven Van Asbroeck <thesven73@gmail.com>]

The fsl_ssi always has a bclk_ratio of 64 in ssi master
mode, no matter the configured word length.

Add a rule which constrains the bclk_ratio to 64 in
ssi master mode.

Signed-off-by: Sven Van Asbroeck <TheSven73@gmail.com>
---
 sound/soc/fsl/fsl_ssi.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/sound/soc/fsl/fsl_ssi.c b/sound/soc/fsl/fsl_ssi.c
index 0a648229e643..1c5b674fe253 100644
--- a/sound/soc/fsl/fsl_ssi.c
+++ b/sound/soc/fsl/fsl_ssi.c
@@ -627,6 +627,29 @@ static void fsl_ssi_setup_ac97(struct fsl_ssi *ssi)
 	regmap_write(regs, REG_SSI_SOR, SSI_SOR_WAIT(3));
 }
 
+static int fsl_ssi_hw_rule_i2s_master(struct snd_pcm_hw_params *params,
+						struct snd_pcm_hw_rule *rule)
+{
+	struct snd_interval *it = hw_param_interval(params,
+					SNDRV_PCM_HW_PARAM_BCLK_RATIO);
+	struct fsl_ssi *ssi = rule->private;
+	struct snd_interval t;
+
+	if (!fsl_ssi_is_i2s_master(ssi))
+		return 0;
+
+	/*
+	 * In i2s master mode, the ssi always generates 32 physical
+	 * bits/channel. This mode always has 2 channels.
+	 * This results in a fixed bclk_ratio of 64.
+	 */
+	memset(&t, 0, sizeof(t));
+	t.min = t.max = 64;
+	t.integer = 1;
+
+	return snd_interval_refine(it, &t);
+}
+
 static int fsl_ssi_startup(struct snd_pcm_substream *substream,
 			   struct snd_soc_dai *dai)
 {
@@ -648,6 +671,12 @@ static int fsl_ssi_startup(struct snd_pcm_substream *substream,
 		snd_pcm_hw_constraint_step(substream->runtime, 0,
 					   SNDRV_PCM_HW_PARAM_PERIOD_SIZE, 2);
 
+	snd_pcm_hw_rule_add(substream->runtime, 0,
+		SNDRV_PCM_HW_PARAM_BCLK_RATIO,
+		fsl_ssi_hw_rule_i2s_master, ssi,
+		SNDRV_PCM_HW_PARAM_FORMAT, SNDRV_PCM_HW_PARAM_CHANNELS,
+		-1);
+
 	return 0;
 }
 
-- 
2.17.1