From a2ef66a047d4521ff6005d43b161aaf2b68841d7 Mon Sep 17 00:00:00 2001 From: Troy Mitchell Date: Mon, 18 May 2026 14:21:08 +0800 Subject: [PATCH 1/2] ASoC: soc-dai: add shared BCLK clock for cross-DAI rate constraints 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 Signed-off-by: Linux RISC-V bot --- 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 6a42812bba8cad..df010a91b35059 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 2f370fda12665d..1719ddcefa4b03 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; From c921546079bcf289dc7e29d1003690059eb23efc Mon Sep 17 00:00:00 2001 From: Troy Mitchell Date: Mon, 18 May 2026 14:21:09 +0800 Subject: [PATCH 2/2] ASoC: soc-pcm: constrain hw_params when DAIs share the same BCLK When multiple CPU DAIs on the same sound card share the same physical BCLK, add a hw_rule during PCM open that constrains the sample rate so the resulting BCLK rate stays consistent across all sharing DAIs. The hw_rule is registered unconditionally for every DAI that has a bclk clock pointer set. The actual peer scanning happens inside the rule callback at hw_refine time: it walks all DAIs on the card, looking for an active peer that shares the same physical BCLK (via clk_is_match()) and has already completed hw_params (checked via dai->symmetric_rate != 0). This ensures the constraint uses the real BCLK rate established by the peer's clk_set_rate() in hw_params, not a stale boot-time default. The first DAI to complete hw_params is unconstrained (no active peer yet); subsequent DAIs are constrained to match. The rule supports two modes: - If the DAI has an explicit bclk_ratio set (e.g. for TDM where BCLK = rate * slots * slot_width), the rate is constrained to active_bclk_rate / bclk_ratio. - Otherwise, the default formula BCLK = rate * channels * sample_bits is used to derive the valid rate range. The constraint is purely additive: DAIs that do not set a bclk clock pointer are completely unaffected. Signed-off-by: Troy Mitchell Signed-off-by: Linux RISC-V bot --- sound/soc/soc-pcm.c | 119 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 119 insertions(+) diff --git a/sound/soc/soc-pcm.c b/sound/soc/soc-pcm.c index 9b12eedb77c331..e75c343b8d4e63 100644 --- a/sound/soc/soc-pcm.c +++ b/sound/soc/soc-pcm.c @@ -12,6 +12,7 @@ #include #include +#include #include #include #include @@ -467,6 +468,117 @@ static int soc_pcm_apply_symmetry(struct snd_pcm_substream *substream, return 0; } +/* + * Shared BCLK constraint: when multiple DAIs share the same physical BCLK, + * constrain hw_params so that the BCLK rate (rate * channels * sample_bits, + * or rate * slots * slot_width for TDM) remains consistent. + */ + +static int soc_pcm_shared_bclk_rule_rate(struct snd_pcm_hw_params *params, + struct snd_pcm_hw_rule *rule) +{ + struct snd_soc_dai *dai = rule->private; + struct snd_soc_card *card = dai->component->card; + struct snd_soc_pcm_runtime *rtd; + struct snd_soc_dai *other_dai; + unsigned long active_bclk_rate = 0; + struct snd_interval *rate = hw_param_interval(params, SNDRV_PCM_HW_PARAM_RATE); + struct snd_interval constraint = { .empty = 1 }; + unsigned int target_rate; + int i; + + /* + * Protect the rtd list traversal. No nesting: this callback runs + * from snd_pcm_hw_refine() which does not hold card->mutex. + */ + guard(mutex)(&card->mutex); + + /* Scan all DAIs on the card for an active peer sharing the same BCLK */ + for_each_card_rtds(card, rtd) { + for_each_rtd_cpu_dais(rtd, i, other_dai) { + if (other_dai == dai) + continue; + if (!other_dai->bclk) + continue; + if (!snd_soc_dai_active(other_dai)) + continue; + /* + * Skip peers whose hw_params hasn't run yet. + * symmetric_rate is set by soc_pcm_set_dai_params() + * after snd_soc_dai_hw_params(), so non-zero means + * the DAI's clk_set_rate() has already executed. + */ + if (!other_dai->symmetric_rate) + continue; + if (!clk_is_match(dai->bclk, other_dai->bclk)) + continue; + + active_bclk_rate = clk_get_rate(other_dai->bclk); + if (active_bclk_rate) + goto found; + } + } + + return 0; + +found: + if (dai->bclk_ratio) { + /* + * Driver has set an explicit BCLK ratio (e.g. for TDM where + * BCLK = rate * slots * slot_width). The only valid rate is + * active_bclk_rate / bclk_ratio. + */ + target_rate = active_bclk_rate / dai->bclk_ratio; + + constraint.min = target_rate; + constraint.max = target_rate; + } else { + struct snd_interval *channels = hw_param_interval(params, + SNDRV_PCM_HW_PARAM_CHANNELS); + struct snd_interval *sample_bits = hw_param_interval(params, + SNDRV_PCM_HW_PARAM_SAMPLE_BITS); + + /* + * Default: BCLK = rate * channels * sample_bits. + * Calculate the range of valid rates given the current + * channel and sample_bits intervals. + */ + if (!channels->min || !sample_bits->min) + return 0; + + constraint.max = active_bclk_rate / + ((unsigned long)channels->min * sample_bits->min); + + if (channels->max && sample_bits->max) + constraint.min = active_bclk_rate / + ((unsigned long)channels->max * sample_bits->max); + else + constraint.min = constraint.max; + } + + constraint.integer = 1; + constraint.empty = 0; + + return snd_interval_refine(rate, &constraint); +} + +static int soc_pcm_apply_shared_bclk(struct snd_pcm_substream *substream, + struct snd_soc_dai *dai) +{ + if (!dai->bclk) + return 0; + + dev_dbg(dai->dev, + "ASoC: registering shared BCLK rate constraint\n"); + + return snd_pcm_hw_rule_add(substream->runtime, 0, + SNDRV_PCM_HW_PARAM_RATE, + soc_pcm_shared_bclk_rule_rate, dai, + SNDRV_PCM_HW_PARAM_CHANNELS, + SNDRV_PCM_HW_PARAM_SAMPLE_BITS, + -1); +} + static int soc_pcm_params_symmetry(struct snd_pcm_substream *substream, struct snd_pcm_hw_params *params) { @@ -903,6 +1015,13 @@ static int __soc_pcm_open(struct snd_soc_pcm_runtime *rtd, if (ret != 0) goto err; } + + /* Shared BCLK constraint across DAIs on the same card */ + for_each_rtd_cpu_dais(rtd, i, dai) { + ret = soc_pcm_apply_shared_bclk(substream, dai); + if (ret != 0) + goto err; + } dynamic: snd_soc_runtime_activate(rtd, substream->stream); ret = 0;