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Mark Brown
3bd860dcf9
Troy Mitchell <troy.mitchell@linux.spacemit.com> says: On some SoCs (e.g. SpacemiT K3), multiple I2S controllers share the same physical BCLK. When one controller is already streaming, the others must use hw_params that result in the same BCLK rate, otherwise the shared clock would be reconfigured and corrupt the active stream. This series adds framework-level support for this constraint: Patch 1 adds the dt-bindings for the spacemit,k3-i2s compatible. The K3 SoC uses the same I2S IP as K1 but requires additional clocks: a dedicated sysclk_div, along with c_sysclk and c_bclk which are shared across multiple I2S controllers. Patch 2 adds a DEFINE_GUARD wrapping snd_soc_card_mutex_lock() and snd_soc_card_mutex_unlock() so that scope-based locking picks up the SND_SOC_CARD_CLASS_RUNTIME lockdep subclass. Patch 3 adds the constraint logic in soc-pcm.c. During PCM open, every DAI that has a bclk clock pointer gets a hw_rule registered unconditionally. The rule callback runs at hw_refine time: it scans the card for an active peer sharing the same physical BCLK (via clk_is_match()) that has already completed hw_params, then constrains the current stream's rate to match the established BCLK rate. The first DAI to complete hw_params is unconstrained; subsequent DAIs must match. Two modes are supported: - Default (I2S): BCLK = rate * channels * sample_bits. The rule derives the valid rate range from the current channel and sample_bits intervals. - Explicit ratio (TDM): if the driver sets dai->bclk_ratio (e.g. slots * slot_width), the rule computes the single valid rate as active_bclk_rate / bclk_ratio. This series was prompted by review feedback on the SpacemiT K3 I2S series, where a vendor-specific fixed-sample-rate property was rejected in favor of a generic framework solution: https://lore.kernel.org/all/afFqgF6ZRwYdfUmL@sirena.co.uk/ Link: https://patch.msgid.link/20260522-i2s-same-blk-v4-0-a71a86faaa20@linux.spacemit.com