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Fri, 22 May 2026 21:34:08 +0800 (CST) X-QQ-SSF: 0000000000000000000000000000000 X-QQ-GoodBg: 0 X-BIZMAIL-ID: 13054678115676240062 EX-QQ-RecipientCnt: 11 From: Troy Mitchell Date: Fri, 22 May 2026 21:33:59 +0800 Subject: [PATCH v4 3/3] ASoC: soc-pcm: constrain hw_params when DAIs share the same BCLK Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260522-i2s-same-blk-v4-3-a71a86faaa20@linux.spacemit.com> References: <20260522-i2s-same-blk-v4-0-a71a86faaa20@linux.spacemit.com> In-Reply-To: <20260522-i2s-same-blk-v4-0-a71a86faaa20@linux.spacemit.com> To: Liam Girdwood , Mark Brown , Jaroslav Kysela , Takashi Iwai , Yixun Lan 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 X-Mailer: b4 0.15.2 X-Developer-Signature: v=1; a=ed25519-sha256; t=1779456837; l=5579; i=troy.mitchell@linux.spacemit.com; s=20250710; h=from:subject:message-id; bh=cj1EjUM699n6DwPiNAQ0TESANNZBoZiYy78W+H/j1Vg=; b=5nr4kKimnGwTMoC+FhkfgLS/mCXu5CIsV4L92oHLVF4Z9cLDNqXJ+YtCWKTBwSCCUtV1K4Y2w +ObzqLfWQidAUeS8hvvGl+u1pFf/Tm0FqXAbex1eVk1vc3TTmoGKR0O X-Developer-Key: i=troy.mitchell@linux.spacemit.com; a=ed25519; pk=lQa7BzLrq8DfZnChqmwJ5qQk8fP2USmY/4xZ2/MSsXc= X-QQ-SENDSIZE: 520 Feedback-ID: esmtpgz:linux.spacemit.com:qybglogicsvrgz:qybglogicsvrgz3a-0 X-QQ-XMAILINFO: ONsBhzqno2d9f6zvjxchYgaKjpHhVNUFyHRrfXzStsSHewDf7O/YFDNg ciyaSsIAGLpSPgAfLVXfpZwSBpjSBD9Exb9+NhC+6LQrgSO3LlHYhFTX1qIagdGdvsr25OD wzegeMxEERkUKac2QyCxlMuXW++FObJSfRqClQcJuSG6eCafRjWOf7GEyCNhoIE2/N8KED/ 5+zfxQngA/P6NI8utRGbVDHdBdVyBsIb6pvNfiuh3Fy5T/FC9ODxtoj2UsuT81Vy81dl+SS wJBK3rrZEo5oI3hmagBTnCRxSfjNfuGvxadrE5ib8S3RLLrnWR6t2MhNLWtlVNunC0K2NBy F9dmzaHMza5WMTMt4w5J8OfBWl+ae11+NmwrFVvTvE/4Zm0dQSo0GWKFj9spCh9Elzx9pKc qktOTtnUOKgi9rbfcDcEh8ChiaOtwHu0VBiQ3y8h7v9ObIvK13fSjVIKvjxOq3O7OExSF/W ro0M46riIRDxd/W8jn4qGYfNObdQPbTNpcOprXodkxeH3tuyz1LyP8Mm0RMKZfhwu762Zqm wA457/c94BwgwTjWFMXzHoKt1mEC8+CJ7LBXzYedHS6TlPtQx6PaPBrc+PnutmlitG07Uz1 3d14ZrGiMDY91g8Qyh/dT6L+A0soc2l6QDVFKDCaa6kddxmn8BbVaxexOmAs1sB5D9NHIoD iObTOrRlJ7GjgR2syqFE2Ta5D0k1gxnGMymxZjWZGygtWNgX5eqtea/FGx+o6iIm6W7w5ZX BXUxuC4Y5mUP7oSYf8YQ31edsPBWfRoU0iiDrz4ckH14vYbdYliuIR+gCM0gfpczYWyOcsj 2XSU38IaMgoYYNllWFgJwwZgkr3gxabuRiRpzlJOWzR5iuAmDcxZNOlpJC2kauZkYTWVAto sYaZyW98TC//6py0x1NDu7hi5+nsfVhp4fXYeIoW/8dK4tQjcB2XZPQujxsK5fEBnd9lIrD 68z2TPuy3GmbrgmiVsf/2XyS1hyBwogtWTqSBhKMvx7J68EGVeNZkHa8psdrCrNWVkmi2Zb sCA8KswfiKZVJ+QnAPgyLzmgOqpOT1fg0HawA7fbGHHZ3dbk7OFCswueqDKM8mE5Vhog/ve yPwT1VV/COfSJ3bGJZHG40qYQVKrW/0xAZ4c5z1H6X9s9tzdPbWqFzsPKx4w2crWRCVmfPF NXCzN0n97aMnAj3jemsXZy+Qap8ZNKQh8/jz X-QQ-XMRINFO: MPJ6Tf5t3I/ylTmHUqvI8+Wpn+Gzalws3A== X-QQ-RECHKSPAM: 0 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 --- 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 25e494c4ed81..0e49290a8c90 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; -- 2.54.0