linux-kernel - [PATCH] ASoC: wm8960: Fix wrong bclk and lrclk with pll enabled for some chips

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Date:   Fri, 19 Mar 2021 18:48:46 +0800
From:   Shengjiu Wang <shengjiu.wang@....com>
To:     lgirdwood@...il.com, broonie@...nel.org, perex@...ex.cz,
        tiwai@...e.com, shengjiu.wang@....com,
        ckeepax@...nsource.cirrus.com, kuninori.morimoto.gx@...esas.com,
        peter.ujfalusi@...com, gustavoars@...nel.org,
        pierre-louis.bossart@...ux.intel.com, daniel.baluta@....com,
        patches@...nsource.cirrus.com, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] ASoC: wm8960: Fix wrong bclk and lrclk with pll enabled for some chips

The input MCLK is 12.288MHz, the desired output sysclk is 11.2896MHz
and sample rate is 44100Hz, with the configuration pllprescale=2,
postscale=sysclkdiv=1, some chip may have wrong bclk
and lrclk output with pll enabled in master mode, but with the
configuration pllprescale=1, postscale=2, the output clock is correct.

>From Datasheet, the PLL performs best when f2 is between
90MHz and 100MHz when the desired sysclk output is 11.2896MHz
or 12.288MHz, so sysclkdiv = 2 (f2/8) is the best choice.

So search available sysclk_divs from 2 to 1 other than from 1 to 2.

Fixes: 84fdc00d519f ("ASoC: codec: wm9860: Refactor PLL out freq search")
Signed-off-by: Shengjiu Wang <shengjiu.wang@....com>
---
 sound/soc/codecs/wm8960.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/sound/soc/codecs/wm8960.c b/sound/soc/codecs/wm8960.c
index df351519a3a6..cda9cd935d4f 100644
--- a/sound/soc/codecs/wm8960.c
+++ b/sound/soc/codecs/wm8960.c
@@ -707,7 +707,13 @@ int wm8960_configure_pll(struct snd_soc_component *component, int freq_in,
 	best_freq_out = -EINVAL;
 	*sysclk_idx = *dac_idx = *bclk_idx = -1;
 
-	for (i = 0; i < ARRAY_SIZE(sysclk_divs); ++i) {
+	/*
+	 * From Datasheet, the PLL performs best when f2 is between
+	 * 90MHz and 100MHz, the desired sysclk output is 11.2896MHz
+	 * or 12.288MHz, then sysclkdiv = 2 is the best choice.
+	 * So search sysclk_divs from 2 to 1 other than from 1 to 2.
+	 */
+	for (i = ARRAY_SIZE(sysclk_divs) - 1; i >= 0; --i) {
 		if (sysclk_divs[i] == -1)
 			continue;
 		for (j = 0; j < ARRAY_SIZE(dac_divs); ++j) {
-- 
2.17.1