[PATCH v3] ASoC: simple-card-utils: add sysclk ordering support

[Stefano Radaelli <stefano.radaelli21@gmail.com>]

From: Stefano Radaelli <stefano.r@variscite.com>

When simple-audio-card programs sysclk for CPU and codec DAIs during
hw_params, the ordering of these calls may matter on some platforms.

Some CPU DAIs finalize or adjust the MCLK rate as part of their
set_sysclk() callback (for example by calling clk_set_rate()). If the
codec sysclk is configured before the CPU DAI applies the final MCLK
rate, the codec may configure its internal clocking based on a
non-final MCLK value.

Such situations can arise depending on the clock provider/consumer
relationship between the CPU DAI and the codec.

Introduce an explicit sysclk ordering enum in simple-card-utils and use
it to control the order of snd_soc_dai_set_sysclk() calls in the mclk-fs
handling path. The default behaviour remains unchanged (codec-first)
to avoid regressions.

Signed-off-by: Stefano Radaelli <stefano.r@variscite.com>
---
v3:
 - DT flag not applicable, not a hardware configuration
 - Introduced enum to support order configuration

v2:
 - Do not change the default sysclk ordering
 - Make the ordering selectable via DT flag
 - Add DT binding documentation
Link: https://patchwork.kernel.org/project/alsa-devel/patch/20260210164506.161810-2-stefano.r@variscite.com/

v1:
 - Changed sysclk order, cpu first, then codec
Link: https://patchwork.kernel.org/project/alsa-devel/patch/20260206134014.143057-1-stefano.r@variscite.com/

 include/sound/simple_card_utils.h     |  7 +++++
 sound/soc/generic/simple-card-utils.c | 44 ++++++++++++++++++++-------
 2 files changed, 40 insertions(+), 11 deletions(-)

diff --git a/include/sound/simple_card_utils.h b/include/sound/simple_card_utils.h
index 69a9c9c4d0e9..137eb795f587 100644
--- a/include/sound/simple_card_utils.h
+++ b/include/sound/simple_card_utils.h
@@ -54,6 +54,12 @@ struct prop_nums {
 	int platforms;
 };
 
+enum simple_util_sysclk_order {
+	SIMPLE_SYSCLK_ORDER_UNSPEC = 0,
+	SIMPLE_SYSCLK_ORDER_CODEC_FIRST,
+	SIMPLE_SYSCLK_ORDER_CPU_FIRST,
+};
+
 struct simple_util_priv {
 	struct snd_soc_card snd_card;
 	struct simple_dai_props {
@@ -63,6 +69,7 @@ struct simple_util_priv {
 		struct snd_soc_codec_conf *codec_conf;
 		struct prop_nums num;
 		unsigned int mclk_fs;
+		enum simple_util_sysclk_order sysclk_order;
 	} *dai_props;
 	struct simple_util_jack hp_jack;
 	struct simple_util_jack mic_jack;
diff --git a/sound/soc/generic/simple-card-utils.c b/sound/soc/generic/simple-card-utils.c
index bdc02e85b089..66030f2bdece 100644
--- a/sound/soc/generic/simple-card-utils.c
+++ b/sound/soc/generic/simple-card-utils.c
@@ -468,9 +468,13 @@ int simple_util_hw_params(struct snd_pcm_substream *substream,
 	struct snd_soc_dai *sdai;
 	struct simple_util_priv *priv = snd_soc_card_get_drvdata(rtd->card);
 	struct simple_dai_props *props = runtime_simple_priv_to_props(priv, rtd);
+	enum simple_util_sysclk_order order = props->sysclk_order;
 	unsigned int mclk, mclk_fs = 0;
 	int i, ret;
 
+	if (order == SIMPLE_SYSCLK_ORDER_UNSPEC)
+		order = SIMPLE_SYSCLK_ORDER_CODEC_FIRST;
+
 	if (props->mclk_fs)
 		mclk_fs = props->mclk_fs;
 
@@ -501,18 +505,36 @@ int simple_util_hw_params(struct snd_pcm_substream *substream,
 				goto end;
 		}
 
-		for_each_rtd_codec_dais(rtd, i, sdai) {
-			pdai = simple_props_to_dai_codec(props, i);
-			ret = snd_soc_dai_set_sysclk(sdai, 0, mclk, pdai->clk_direction);
-			if (ret && ret != -ENOTSUPP)
-				goto end;
-		}
+		if (order == SIMPLE_SYSCLK_ORDER_CPU_FIRST) {
+			/* CPU first */
+			for_each_rtd_cpu_dais(rtd, i, sdai) {
+				pdai = simple_props_to_dai_cpu(props, i);
+				ret = snd_soc_dai_set_sysclk(sdai, 0, mclk, pdai->clk_direction);
+				if (ret && ret != -ENOTSUPP)
+					goto end;
+			}
 
-		for_each_rtd_cpu_dais(rtd, i, sdai) {
-			pdai = simple_props_to_dai_cpu(props, i);
-			ret = snd_soc_dai_set_sysclk(sdai, 0, mclk, pdai->clk_direction);
-			if (ret && ret != -ENOTSUPP)
-				goto end;
+			for_each_rtd_codec_dais(rtd, i, sdai) {
+				pdai = simple_props_to_dai_codec(props, i);
+				ret = snd_soc_dai_set_sysclk(sdai, 0, mclk, pdai->clk_direction);
+				if (ret && ret != -ENOTSUPP)
+					goto end;
+			}
+		} else {
+			/* default: codec first */
+			for_each_rtd_codec_dais(rtd, i, sdai) {
+				pdai = simple_props_to_dai_codec(props, i);
+				ret = snd_soc_dai_set_sysclk(sdai, 0, mclk, pdai->clk_direction);
+				if (ret && ret != -ENOTSUPP)
+					goto end;
+			}
+
+			for_each_rtd_cpu_dais(rtd, i, sdai) {
+				pdai = simple_props_to_dai_cpu(props, i);
+				ret = snd_soc_dai_set_sysclk(sdai, 0, mclk, pdai->clk_direction);
+				if (ret && ret != -ENOTSUPP)
+					goto end;
+			}
 		}
 	}
 

base-commit: b7ff7151e653aa296ab6c5495b2c1ab7c21eb250
-- 
2.47.3