linux-kernel - [PATCH 05/12] ASoC: cs42l42: Set correct SRC MCLK

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Message-ID: <20210810153759.24333-6-rf@opensource.cirrus.com>
Date:   Tue, 10 Aug 2021 16:37:52 +0100
From:   Richard Fitzgerald <rf@...nsource.cirrus.com>
To:     <broonie@...nel.org>
CC:     <alsa-devel@...a-project.org>, <patches@...nsource.cirrus.com>,
        <linux-kernel@...r.kernel.org>,
        Richard Fitzgerald <rf@...nsource.cirrus.com>
Subject: [PATCH 05/12] ASoC: cs42l42: Set correct SRC MCLK

According to the datasheet the SRC MCLK must be as near as possible to
(125 * sample rate). This means it should be ~6MHz for rates up to 48k
and ~12MHz for rates above that. As per datasheet table 4-21.

Signed-off-by: Richard Fitzgerald <rf@...nsource.cirrus.com>
---
 sound/soc/codecs/cs42l42.c | 60 ++++++++++++++++++++++++++++++----------------
 sound/soc/codecs/cs42l42.h |  1 +
 2 files changed, 40 insertions(+), 21 deletions(-)

diff --git a/sound/soc/codecs/cs42l42.c b/sound/soc/codecs/cs42l42.c
index 1893d3694570..14fd70c56891 100644
--- a/sound/soc/codecs/cs42l42.c
+++ b/sound/soc/codecs/cs42l42.c
@@ -663,22 +663,6 @@ static int cs42l42_pll_config(struct snd_soc_component *component)
 					CS42L42_FSYNC_PULSE_WIDTH_MASK,
 					CS42L42_FRAC1_VAL(fsync - 1) <<
 					CS42L42_FSYNC_PULSE_WIDTH_SHIFT);
-			/* Set the sample rates (96k or lower) */
-			snd_soc_component_update_bits(component, CS42L42_FS_RATE_EN,
-					CS42L42_FS_EN_MASK,
-					(CS42L42_FS_EN_IASRC_96K |
-					CS42L42_FS_EN_OASRC_96K) <<
-					CS42L42_FS_EN_SHIFT);
-			/* Set the input/output internal MCLK clock ~12 MHz */
-			snd_soc_component_update_bits(component, CS42L42_IN_ASRC_CLK,
-					CS42L42_CLK_IASRC_SEL_MASK,
-					CS42L42_CLK_IASRC_SEL_12 <<
-					CS42L42_CLK_IASRC_SEL_SHIFT);
-			snd_soc_component_update_bits(component,
-					CS42L42_OUT_ASRC_CLK,
-					CS42L42_CLK_OASRC_SEL_MASK,
-					CS42L42_CLK_OASRC_SEL_12 <<
-					CS42L42_CLK_OASRC_SEL_SHIFT);
 			if (pll_ratio_table[i].mclk_src_sel == 0) {
 				/* Pass the clock straight through */
 				snd_soc_component_update_bits(component,
@@ -741,6 +725,34 @@ static int cs42l42_pll_config(struct snd_soc_component *component)
 	return -EINVAL;
 }
 
+static void cs42l42_src_config(struct snd_soc_component *component, unsigned int sample_rate)
+{
+	unsigned int fs;
+
+	/* SRC MCLK must be as close as possible to 125 * sample rate */
+	if (sample_rate <= 48000)
+		fs = CS42L42_CLK_IASRC_SEL_6;
+	else
+		fs = CS42L42_CLK_IASRC_SEL_12;
+
+	/* Set the sample rates (96k or lower) */
+	snd_soc_component_update_bits(component,
+				      CS42L42_FS_RATE_EN,
+				      CS42L42_FS_EN_MASK,
+				      (CS42L42_FS_EN_IASRC_96K |
+				       CS42L42_FS_EN_OASRC_96K) <<
+				      CS42L42_FS_EN_SHIFT);
+
+	snd_soc_component_update_bits(component,
+				      CS42L42_IN_ASRC_CLK,
+				      CS42L42_CLK_IASRC_SEL_MASK,
+				      fs << CS42L42_CLK_IASRC_SEL_SHIFT);
+	snd_soc_component_update_bits(component,
+				      CS42L42_OUT_ASRC_CLK,
+				      CS42L42_CLK_OASRC_SEL_MASK,
+				      fs << CS42L42_CLK_OASRC_SEL_SHIFT);
+}
+
 static int cs42l42_set_dai_fmt(struct snd_soc_dai *codec_dai, unsigned int fmt)
 {
 	struct snd_soc_component *component = codec_dai->component;
@@ -831,6 +843,7 @@ static int cs42l42_pcm_hw_params(struct snd_pcm_substream *substream,
 	unsigned int channels = params_channels(params);
 	unsigned int width = (params_width(params) / 8) - 1;
 	unsigned int val = 0;
+	int ret;
 
 	cs42l42->srate = params_rate(params);
 	cs42l42->bclk = snd_soc_params_to_bclk(params);
@@ -884,11 +897,16 @@ static int cs42l42_pcm_hw_params(struct snd_pcm_substream *substream,
 		break;
 	}
 
-	/* Configure the PLL if this is the first active stream */
-	if (!cs42l42->stream_use)
-		return cs42l42_pll_config(component);
-	else
-		return 0;
+	/* Configure clocking only if this is the first active stream */
+	if (!cs42l42->stream_use) {
+		ret = cs42l42_pll_config(component);
+		if (ret)
+			return ret;
+
+		cs42l42_src_config(component, params_rate(params));
+	}
+
+	return 0;
 }
 
 static int cs42l42_set_sysclk(struct snd_soc_dai *dai,
diff --git a/sound/soc/codecs/cs42l42.h b/sound/soc/codecs/cs42l42.h
index 8734f6828f3e..addb6560c649 100644
--- a/sound/soc/codecs/cs42l42.h
+++ b/sound/soc/codecs/cs42l42.h
@@ -288,6 +288,7 @@
 #define CS42L42_IN_ASRC_CLK		(CS42L42_PAGE_12 + 0x0A)
 #define CS42L42_CLK_IASRC_SEL_SHIFT	0
 #define CS42L42_CLK_IASRC_SEL_MASK	(1 << CS42L42_CLK_IASRC_SEL_SHIFT)
+#define CS42L42_CLK_IASRC_SEL_6		0
 #define CS42L42_CLK_IASRC_SEL_12	1
 
 #define CS42L42_OUT_ASRC_CLK		(CS42L42_PAGE_12 + 0x0B)
-- 
2.11.0