[PATCH v4 1/3] ASoC: soc-dai: add shared BCLK clock for cross-DAI rate constraints

From: Troy Mitchell <troy.mitchell@linux.spacemit.com>
To: Liam Girdwood <lgirdwood@gmail.com>,
	Mark Brown <broonie@kernel.org>,
	 Jaroslav Kysela <perex@perex.cz>, Takashi Iwai <tiwai@suse.com>,
	 Yixun Lan <dlan@kernel.org>
Cc: linux-sound@vger.kernel.org, linux-kernel@vger.kernel.org,
	 linux-riscv@lists.infradead.org, spacemit@lists.linux.dev,
	 jinmei.wei@spacemit.com,
	Troy Mitchell <troy.mitchell@linux.spacemit.com>
Subject: [PATCH v4 1/3] ASoC: soc-dai: add shared BCLK clock for cross-DAI rate constraints
Date: Fri, 22 May 2026 21:33:57 +0800	[thread overview]
Message-ID: <20260522-i2s-same-blk-v4-1-a71a86faaa20@linux.spacemit.com> (raw)
In-Reply-To: <20260522-i2s-same-blk-v4-0-a71a86faaa20@linux.spacemit.com>

Add a bclk field to struct snd_soc_dai and a helper function
snd_soc_dai_set_bclk_clk() that platform drivers can use to declare
which clock is their BCLK.

Also cache the bclk_ratio in snd_soc_dai_set_bclk_ratio() so that
the framework can use it later in hw_rule evaluation for TDM
configurations where BCLK = rate * slots * slot_width.

When multiple DAIs on the same card share the same physical BCLK
(detected via clk_is_match()), the ASoC core can automatically
constrain their hw_params so that the resulting BCLK rates are
compatible. This commit adds the data structure support; the actual
constraint logic follows in the next patch.

Signed-off-by: Troy Mitchell <troy.mitchell@linux.spacemit.com>
---
 include/sound/soc-dai.h |  7 +++++++
 sound/soc/soc-dai.c     | 18 ++++++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/include/sound/soc-dai.h b/include/sound/soc-dai.h
index 6a42812bba8c..df010a91b350 100644
--- a/include/sound/soc-dai.h
+++ b/include/sound/soc-dai.h
@@ -17,6 +17,7 @@
 struct snd_pcm_substream;
 struct snd_soc_dapm_widget;
 struct snd_compr_stream;
+struct clk;
 
 /*
  * DAI hardware audio formats.
@@ -188,6 +189,8 @@ int snd_soc_dai_set_pll(struct snd_soc_dai *dai,
 
 int snd_soc_dai_set_bclk_ratio(struct snd_soc_dai *dai, unsigned int ratio);
 
+void snd_soc_dai_set_bclk_clk(struct snd_soc_dai *dai, struct clk *bclk);
+
 /* Digital Audio interface formatting */
 int snd_soc_dai_get_fmt_max_priority(const struct snd_soc_pcm_runtime *rtd);
 u64 snd_soc_dai_get_fmt(const struct snd_soc_dai *dai, int priority);
@@ -473,6 +476,10 @@ struct snd_soc_dai {
 	unsigned int symmetric_channels;
 	unsigned int symmetric_sample_bits;
 
+	/* shared BCLK clock for cross-DAI rate constraints */
+	struct clk *bclk;
+	unsigned int bclk_ratio; /* BCLK = rate * bclk_ratio (0 = use channels * sample_bits) */
+
 	/* parent platform/codec */
 	struct snd_soc_component *component;
 
diff --git a/sound/soc/soc-dai.c b/sound/soc/soc-dai.c
index 2f370fda1266..1719ddcefa4b 100644
--- a/sound/soc/soc-dai.c
+++ b/sound/soc/soc-dai.c
@@ -116,10 +116,28 @@ int snd_soc_dai_set_bclk_ratio(struct snd_soc_dai *dai, unsigned int ratio)
 	    dai->driver->ops->set_bclk_ratio)
 		ret = dai->driver->ops->set_bclk_ratio(dai, ratio);
 
+	if (!ret)
+		dai->bclk_ratio = ratio;
+
 	return soc_dai_ret(dai, ret);
 }
 EXPORT_SYMBOL_GPL(snd_soc_dai_set_bclk_ratio);
 
+/**
+ * snd_soc_dai_set_bclk_clk - set the BCLK clock for shared clock detection
+ * @dai: DAI
+ * @bclk: BCLK clock pointer (or NULL to clear)
+ *
+ * When multiple DAIs share the same physical BCLK (detected via
+ * clk_is_match()), the ASoC core will automatically constrain their
+ * hw_params so that the resulting BCLK rates are compatible.
+ */
+void snd_soc_dai_set_bclk_clk(struct snd_soc_dai *dai, struct clk *bclk)
+{
+	dai->bclk = bclk;
+}
+EXPORT_SYMBOL_GPL(snd_soc_dai_set_bclk_clk);
+
 int snd_soc_dai_get_fmt_max_priority(const struct snd_soc_pcm_runtime *rtd)
 {
 	struct snd_soc_dai *dai;

-- 
2.54.0


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