On Fri, Dec 20, 2013 at 12:39:38PM +0200, Jyri Sarha wrote:

Add machine driver support for BeagleBone-Black and other boards with
tilcdc support and NXP TDA998X HDMI transmitter connected to McASP
port in I2S mode. The 44100 Hz sample-rate and it's multiples can not
be supported on Beaglebone-Black because of limited clock-rate

Can the drivers infer this from the clocks?

support. The only supported sample format is SNDRV_PCM_FORMAT_S32_LE.
The 8 least significant bits are ignored.

Where does this constraint come from?

+	struct snd_soc_card_drvdata_davinci *drvdata =
+		(struct snd_soc_card_drvdata_davinci *)
+		snd_soc_card_get_drvdata(soc_card);

Again with the casting.

+	runtime->hw.rate_min = drvdata->rate_constraint->list[0];
+	runtime->hw.rate_max = drvdata->rate_constraint->list[
+		drvdata->rate_constraint->count - 1];
+	runtime->hw.rates = SNDRV_PCM_RATE_KNOT;
+
+	snd_pcm_hw_constraint_list(runtime, 0, SNDRV_PCM_HW_PARAM_RATE,
+				   drvdata->rate_constraint);
+	snd_pcm_hw_constraint_minmax(runtime, SNDRV_PCM_HW_PARAM_CHANNELS,
+				     2, 2);

Why not just set all this statically when registering the DAI?

+static unsigned int evm_get_bclk(struct snd_pcm_hw_params *params)
+{
+	int sample_size = snd_pcm_format_width(params_format(params));
+	int rate = params_rate(params);
+	int channels = params_channels(params);
+
+	return sample_size * channels * rate;
+}

snd_soc_params_to_frame_size().

+static int evm_tda998x_hw_params(struct snd_pcm_substream *substream,
+				 struct snd_pcm_hw_params *params)
+{
+	struct snd_soc_pcm_runtime *rtd = substream->private_data;
+	struct snd_soc_dai *cpu_dai = rtd->cpu_dai;
+	struct snd_soc_codec *codec = rtd->codec;
+	struct snd_soc_card *soc_card = codec->card;
+	struct platform_device *pdev = to_platform_device(soc_card->dev);
+	unsigned int bclk_freq = evm_get_bclk(params);
+	unsigned sysclk = ((struct snd_soc_card_drvdata_davinci *)
+			   snd_soc_card_get_drvdata(soc_card))->sysclk;
+	int ret;
+
+	ret = snd_soc_dai_set_clkdiv(cpu_dai, 1, sysclk / bclk_freq);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "can't set CPU DAI clock divider %d\n",
+			ret);
+		return ret;
+	}

This looks like something the DAI driver ought to be able to work out
for itself based on the clock rate and sample format.

+static unsigned int tda998x_hdmi_rates[] = {
+	32000,
+	44100,
+	48000,
+	88200,
+	96000,
+};

The changelog said that 44.1kHz and its multiples couldn't be supported
- is that just the multiples?

+static struct snd_pcm_hw_constraint_list *evm_tda998x_rate_constraint(
+	struct snd_soc_card *soc_card)
+{
+	struct platform_device *pdev = to_platform_device(soc_card->dev);
+	unsigned sysclk = ((struct snd_soc_card_drvdata_davinci *)
+			   snd_soc_card_get_drvdata(soc_card))->sysclk;
+	struct snd_pcm_hw_constraint_list *ret;
+	unsigned int *rates;
+	int i = 0, j = 0;
+
+	ret = devm_kzalloc(soc_card->dev, sizeof(*ret) +
+			   sizeof(tda998x_hdmi_rates), GFP_KERNEL);
+	if (!ret) {
+		dev_err(&pdev->dev, "Unable to allocate rate constraint!\n");

OOM is already very verbose, don't bother.

+		return NULL;
+	}
+
+	rates = (unsigned int *)&ret[1];
+	ret->list = rates;
+	ret->mask = 0;
+	for (; i < ARRAY_SIZE(tda998x_hdmi_rates); i++) {

This is all very hard to read.  Why has the assignment of i been moved
up to the declaration rather than put here as is idiomatic, what's all
the casting going on with ret and in general?