ASoC: nau8821: Implement hw constraint for rates

nau8821 driver restricts the sample rate with over sampling rate, but
currently it barely bails out at hw_params with -EINVAL error (with a
kernel message); this doesn't help for user-space to recognize which
rate can be actually used.

This patch introduces the proper hw constraint for adjusting the
available range of the sample rate depending on the OSR setup, as well
as some code cleanup, for improving the communication with
user-space.  Now applications can know the valid rate beforehand and
reduces the rate appropriately without errors.
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Link: https://lore.kernel.org/r/20220823081000.2965-2-tiwai@suse.deSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/nau8821.c

@@ -670,28 +670,40 @@ static const struct snd_soc_dapm_route nau8821_dapm_routes[] = {
 	{"HPOR", NULL, "Class G"},
 };
 
-static int nau8821_clock_check(struct nau8821 *nau8821,
-	int stream, int rate, int osr)
+static const struct nau8821_osr_attr *
+nau8821_get_osr(struct nau8821 *nau8821, int stream)
 {
-	int osrate = 0;
+	unsigned int osr;
 
 	if (stream == SNDRV_PCM_STREAM_PLAYBACK) {
+		regmap_read(nau8821->regmap, NAU8821_R2C_DAC_CTRL1, &osr);
+		osr &= NAU8821_DAC_OVERSAMPLE_MASK;
 		if (osr >= ARRAY_SIZE(osr_dac_sel))
-			return -EINVAL;
-		osrate = osr_dac_sel[osr].osr;
+			return NULL;
+		return &osr_dac_sel[osr];
 	} else {
+		regmap_read(nau8821->regmap, NAU8821_R2B_ADC_RATE, &osr);
+		osr &= NAU8821_ADC_SYNC_DOWN_MASK;
 		if (osr >= ARRAY_SIZE(osr_adc_sel))
-			return -EINVAL;
-		osrate = osr_adc_sel[osr].osr;
+			return NULL;
+		return &osr_adc_sel[osr];
 	}
+}
 
-	if (!osrate || rate * osrate > CLK_DA_AD_MAX) {
-		dev_err(nau8821->dev,
-			"exceed the maximum frequency of CLK_ADC or CLK_DAC");
+static int nau8821_dai_startup(struct snd_pcm_substream *substream,
+			       struct snd_soc_dai *dai)
+{
+	struct snd_soc_component *component = dai->component;
+	struct nau8821 *nau8821 = snd_soc_component_get_drvdata(component);
+	const struct nau8821_osr_attr *osr;
+
+	osr = nau8821_get_osr(nau8821, substream->stream);
+	if (!osr || !osr->osr)
 		return -EINVAL;
-	}
 
-	return 0;
+	return snd_pcm_hw_constraint_minmax(substream->runtime,
+					    SNDRV_PCM_HW_PARAM_RATE,
+					    0, CLK_DA_AD_MAX / osr->osr);
 }
 
 static int nau8821_hw_params(struct snd_pcm_substream *substream,
@@ -699,7 +711,8 @@ static int nau8821_hw_params(struct snd_pcm_substream *substream,
 {
 	struct snd_soc_component *component = dai->component;
 	struct nau8821 *nau8821 = snd_soc_component_get_drvdata(component);
-	unsigned int val_len = 0, osr, ctrl_val, bclk_fs, clk_div;
+	unsigned int val_len = 0, ctrl_val, bclk_fs, clk_div;
+	const struct nau8821_osr_attr *osr;
 
 	nau8821->fs = params_rate(params);
 	/* CLK_DAC or CLK_ADC = OSR * FS
@@ -708,27 +721,19 @@ static int nau8821_hw_params(struct snd_pcm_substream *substream,
 	 * values must be selected such that the maximum frequency is less
 	 * than 6.144 MHz.
 	 */
-	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {
-		regmap_read(nau8821->regmap, NAU8821_R2C_DAC_CTRL1, &osr);
-		osr &= NAU8821_DAC_OVERSAMPLE_MASK;
-		if (nau8821_clock_check(nau8821, substream->stream,
-			nau8821->fs, osr)) {
-			return -EINVAL;
-		}
+	osr = nau8821_get_osr(nau8821, substream->stream);
+	if (!osr || !osr->osr)
+		return -EINVAL;
+	if (nau8821->fs * osr->osr > CLK_DA_AD_MAX)
+		return -EINVAL;
+	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
 		regmap_update_bits(nau8821->regmap, NAU8821_R03_CLK_DIVIDER,
 			NAU8821_CLK_DAC_SRC_MASK,
-			osr_dac_sel[osr].clk_src << NAU8821_CLK_DAC_SRC_SFT);
-	} else {
-		regmap_read(nau8821->regmap, NAU8821_R2B_ADC_RATE, &osr);
-		osr &= NAU8821_ADC_SYNC_DOWN_MASK;
-		if (nau8821_clock_check(nau8821, substream->stream,
-			nau8821->fs, osr)) {
-			return -EINVAL;
-		}
+			osr->clk_src << NAU8821_CLK_DAC_SRC_SFT);
+	else
 		regmap_update_bits(nau8821->regmap, NAU8821_R03_CLK_DIVIDER,
 			NAU8821_CLK_ADC_SRC_MASK,
-			osr_adc_sel[osr].clk_src << NAU8821_CLK_ADC_SRC_SFT);
-	}
+			osr->clk_src << NAU8821_CLK_ADC_SRC_SFT);
 
 	/* make BCLK and LRC divde configuration if the codec as master. */
 	regmap_read(nau8821->regmap, NAU8821_R1D_I2S_PCM_CTRL2, &ctrl_val);
@@ -843,6 +848,7 @@ static int nau8821_digital_mute(struct snd_soc_dai *dai, int mute,
 }
 
 static const struct snd_soc_dai_ops nau8821_dai_ops = {
+	.startup = nau8821_dai_startup,
 	.hw_params = nau8821_hw_params,
 	.set_fmt = nau8821_set_dai_fmt,
 	.mute_stream = nau8821_digital_mute,