linux-kernel - [PATCH v2] ASoC: fsl_ssi: Fix bclk calculation for mono channel

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Message-Id: <b5cf5e3cc39c62f6bb3660b7588b037ffc57f780.1592200690.git.shengjiu.wang@nxp.com>
Date:   Mon, 15 Jun 2020 13:56:18 +0800
From:   Shengjiu Wang <shengjiu.wang@....com>
To:     timur@...nel.org, nicoleotsuka@...il.com, Xiubo.Lee@...il.com,
        festevam@...il.com, broonie@...nel.org, perex@...ex.cz,
        tiwai@...e.com, alsa-devel@...a-project.org
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2] ASoC: fsl_ssi: Fix bclk calculation for mono channel

For mono channel, SSI will switch to Normal mode.

In Normal mode and Network mode, the Word Length Control bits
control the word length divider in clock generator, which is
different with I2S Master mode (the word length is fixed to
32bit), it should be the value of params_width(hw_params).

The condition "slots == 2" is not good for I2S Master mode,
because for Network mode and Normal mode, the slots can also
be 2. Then we need to use (ssi->i2s_net & SSI_SCR_I2S_MODE_MASK)
to check if it is I2S Master mode.

So we refine the famula for mono channel, otherwise there
will be sound issue for S24_LE.

Fixes: b0a7043d5c2c ("ASoC: fsl_ssi: Caculate bit clock rate using slot number and width")
Signed-off-by: Shengjiu Wang <shengjiu.wang@....com>
---
changes in v2
- refine patch for Network mode and Normal mode.

 sound/soc/fsl/fsl_ssi.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/sound/soc/fsl/fsl_ssi.c b/sound/soc/fsl/fsl_ssi.c
index bad89b0d129e..cbf67d132fda 100644
--- a/sound/soc/fsl/fsl_ssi.c
+++ b/sound/soc/fsl/fsl_ssi.c
@@ -678,7 +678,8 @@ static int fsl_ssi_set_bclk(struct snd_pcm_substream *substream,
 	struct regmap *regs = ssi->regs;
 	u32 pm = 999, div2, psr, stccr, mask, afreq, factor, i;
 	unsigned long clkrate, baudrate, tmprate;
-	unsigned int slots = params_channels(hw_params);
+	unsigned int channels = params_channels(hw_params);
+	unsigned int slots;
 	unsigned int slot_width = 32;
 	u64 sub, savesub = 100000;
 	unsigned int freq;
@@ -688,9 +689,15 @@ static int fsl_ssi_set_bclk(struct snd_pcm_substream *substream,
 	/* Override slots and slot_width if being specifically set... */
 	if (ssi->slots)
 		slots = ssi->slots;
-	/* ...but keep 32 bits if slots is 2 -- I2S Master mode */
-	if (ssi->slot_width && slots != 2)
-		slot_width = ssi->slot_width;
+	else
+		/* Apply two slots for mono channel, because DC = 2 */
+		slots = (channels == 1) ? 2 : channels;
+
+	/* ...but keep 32 bits if I2S Master mode */
+	if ((ssi->i2s_net & SSI_SCR_I2S_MODE_MASK) != SSI_SCR_I2S_MODE_MASTER ||
+	    channels == 1)
+		slot_width = ssi->slot_width ? ssi->slot_width :
+			     params_width(hw_params);
 
 	/* Generate bit clock based on the slot number and slot width */
 	freq = slots * slot_width * params_rate(hw_params);
-- 
2.21.0