[PATCH 4.14 23/68] ASoC: wm8960: Fix wrong bclk and lrclk with pll enabled for some chips

Greg Kroah-Hartman
2021-04-15T14:58:41Z

From: Shengjiu Wang <shengjiu.wang@nxp.com>

[ Upstream commit 16b82e75c15a7dbd564ea3654f3feb61df9e1e6f ]

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@nxp.com>
Acked-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Link: https://lore.kernel.org/r/1616150926-22892-1-git-send-email-shengjiu.wang@nxp.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 9ed455700954..228ab7bd314d 100644
--- a/sound/soc/codecs/wm8960.c
+++ b/sound/soc/codecs/wm8960.c
@@ -710,7 +710,13 @@ int wm8960_configure_pll(struct snd_soc_codec *codec, 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) {
--
2.30.2