From 6061300141166cbbb88e79666973a593758e630d Mon Sep 17 00:00:00 2001 From: Troy Mitchell Date: Fri, 22 May 2026 21:33:57 +0800 Subject: [PATCH 1/3] 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 07553e7eae51d0c7f4e1e114eefd245b4f5d410f Mon Sep 17 00:00:00 2001 From: Troy Mitchell Date: Fri, 22 May 2026 21:33:58 +0800 Subject: [PATCH 2/3] ASoC: soc-pcm: add DEFINE_GUARD for snd_soc_card_mutex Define a guard class wrapping snd_soc_card_mutex_lock() and snd_soc_card_mutex_unlock() so that scope-based locking can be used while still picking up the SND_SOC_CARD_CLASS_RUNTIME lockdep subclass. Signed-off-by: Troy Mitchell Signed-off-by: Linux RISC-V bot --- sound/soc/soc-pcm.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/sound/soc/soc-pcm.c b/sound/soc/soc-pcm.c index 9b12eedb77c331..25e494c4ed8129 100644 --- a/sound/soc/soc-pcm.c +++ b/sound/soc/soc-pcm.c @@ -26,6 +26,9 @@ #include #include + +DEFINE_GUARD(snd_soc_card_mutex, struct snd_soc_card *, + snd_soc_card_mutex_lock(_T), snd_soc_card_mutex_unlock(_T)) #define soc_pcm_ret(rtd, ret) _soc_pcm_ret(rtd, __func__, ret) static inline int _soc_pcm_ret(struct snd_soc_pcm_runtime *rtd, const char *func, int ret) From 12bcb8f87e618e8241d61341e77d7cb20b9a3530 Mon Sep 17 00:00:00 2001 From: Troy Mitchell Date: Fri, 22 May 2026 21:33:59 +0800 Subject: [PATCH 3/3] 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 rule callback scans all DAIs on the card at hw_refine time, 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 | 116 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 116 insertions(+) diff --git a/sound/soc/soc-pcm.c b/sound/soc/soc-pcm.c index 25e494c4ed8129..0e49290a8c903b 100644 --- a/sound/soc/soc-pcm.c +++ b/sound/soc/soc-pcm.c @@ -12,6 +12,7 @@ #include #include +#include #include #include #include @@ -470,6 +471,114 @@ 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 with the ASoC card mutex helper. */ + guard(snd_soc_card_mutex)(card); + + /* 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) { @@ -906,6 +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;