[PATCH 4.19 113/148] ASoC: meson: axg-tdm-interface: fix mclk setup without mclk-fs

Sasha Levin
2024-03-24T23:52:23Z

From: Jerome Brunet <jbrunet@baylibre.com>

[ Upstream commit e3741a8d28a1137f8b19ae6f3d6e3be69a454a0a ]

By default, when mclk-fs is not provided, the tdm-interface driver
requests an MCLK that is 4x the bit clock, SCLK.

However there is no justification for this:

* If the codec needs MCLK for its operation, mclk-fs is expected to be set
according to the codec requirements.
* If the codec does not need MCLK the minimum is 2 * SCLK, because this is
minimum the divider between SCLK and MCLK can do.

Multiplying by 4 may cause problems because the PLL limit may be reached
sooner than it should, so use 2x instead.

Fixes: d60e4f1e4be5 ("ASoC: meson: add tdm interface driver")
Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Link: https://msgid.link/r/20240223175116.2005407-2-jbrunet@baylibre.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
sound/soc/meson/axg-tdm-interface.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/sound/soc/meson/axg-tdm-interface.c b/sound/soc/meson/axg-tdm-interface.c
index 01cc551a8e3fa..2a7ea41fc49e5 100644
--- a/sound/soc/meson/axg-tdm-interface.c
+++ b/sound/soc/meson/axg-tdm-interface.c
@@ -258,8 +258,8 @@ static int axg_tdm_iface_set_sclk(struct snd_soc_dai *dai,
srate = iface->slots * iface->slot_width * params_rate(params);

if (!iface->mclk_rate) {
- /* If no specific mclk is requested, default to bit clock * 4 */
- clk_set_rate(iface->mclk, 4 * srate);
+ /* If no specific mclk is requested, default to bit clock * 2 */
+ clk_set_rate(iface->mclk, 2 * srate);
} else {
/* Check if we can actually get the bit clock from mclk */
if (iface->mclk_rate % srate) {
--
2.43.0