linux-kernel - [PATCH 5.4 131/183] ASoC: meson: axg-tdm-interface: fix mclk setup without mclk-fs

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Message-ID: <20240324234638.1355609-132-sashal@kernel.org>
Date: Sun, 24 Mar 2024 19:45:44 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Jerome Brunet <jbrunet@...libre.com>,
	Mark Brown <broonie@...nel.org>,
	Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.4 131/183] ASoC: meson: axg-tdm-interface: fix mclk setup without mclk-fs

From: Jerome Brunet <jbrunet@...libre.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@...libre.com>
Link: https://msgid.link/r/20240223175116.2005407-2-jbrunet@baylibre.com
Signed-off-by: Mark Brown <broonie@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.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 f5a431b8de6c3..34aff050caf25 100644
--- a/sound/soc/meson/axg-tdm-interface.c
+++ b/sound/soc/meson/axg-tdm-interface.c
@@ -266,8 +266,8 @@ 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