ASoC: xilinx: xlnx_formatter_pcm: Handle sysclk setting

This driver did not set the MM2S Fs Multiplier Register to the proper
value for playback streams. This needs to be set to the sample rate to
MCLK multiplier, or random stream underflows can occur on the downstream
I2S transmitter.

Store the sysclk value provided via the set_sysclk callback and use that
in conjunction with the sample rate in the hw_params callback to calculate
the proper value to set for this register.

Fixes: 6f6c3c36 ("ASoC: xlnx: add pcm formatter platform driver")
Signed-off-by: Robert Hancock <robert.hancock@calian.com>
Link: https://lore.kernel.org/r/20220120195832.1742271-2-robert.hancock@calian.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/xilinx/xlnx_formatter_pcm.c

@@ -84,6 +84,7 @@ struct xlnx_pcm_drv_data {
 	struct snd_pcm_substream *play_stream;
 	struct snd_pcm_substream *capture_stream;
 	struct clk *axi_clk;
+	unsigned int sysclk;
 };
 
 /*
@@ -314,6 +315,15 @@ static irqreturn_t xlnx_s2mm_irq_handler(int irq, void *arg)
 	return IRQ_NONE;
 }
 
+static int xlnx_formatter_set_sysclk(struct snd_soc_component *component,
+				     int clk_id, int source, unsigned int freq, int dir)
+{
+	struct xlnx_pcm_drv_data *adata = dev_get_drvdata(component->dev);
+
+	adata->sysclk = freq;
+	return 0;
+}
+
 static int xlnx_formatter_pcm_open(struct snd_soc_component *component,
 				   struct snd_pcm_substream *substream)
 {
@@ -450,11 +460,25 @@ static int xlnx_formatter_pcm_hw_params(struct snd_soc_component *component,
 	u64 size;
 	struct snd_pcm_runtime *runtime = substream->runtime;
 	struct xlnx_pcm_stream_param *stream_data = runtime->private_data;
+	struct xlnx_pcm_drv_data *adata = dev_get_drvdata(component->dev);
 
 	active_ch = params_channels(params);
 	if (active_ch > stream_data->ch_limit)
 		return -EINVAL;
 
+	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK &&
+	    adata->sysclk) {
+		unsigned int mclk_fs = adata->sysclk / params_rate(params);
+
+		if (adata->sysclk % params_rate(params) != 0) {
+			dev_warn(component->dev, "sysclk %u not divisible by rate %u\n",
+				 adata->sysclk, params_rate(params));
+			return -EINVAL;
+		}
+
+		writel(mclk_fs, stream_data->mmio + XLNX_AUD_FS_MULTIPLIER);
+	}
+
 	if (substream->stream == SNDRV_PCM_STREAM_CAPTURE &&
 	    stream_data->xfer_mode == AES_TO_PCM) {
 		val = readl(stream_data->mmio + XLNX_AUD_STS);
@@ -552,6 +576,7 @@ static int xlnx_formatter_pcm_new(struct snd_soc_component *component,
 
 static const struct snd_soc_component_driver xlnx_asoc_component = {
 	.name		= DRV_NAME,
+	.set_sysclk	= xlnx_formatter_set_sysclk,
 	.open		= xlnx_formatter_pcm_open,
 	.close		= xlnx_formatter_pcm_close,
 	.hw_params	= xlnx_formatter_pcm_hw_params,