Revision 72a77d7631c6e392677c0134343cf5edcd3a4572 authored by Richard Fitzgerald on 29 January 2024, 16:27:26 UTC, committed by Mark Brown on 01 February 2024, 12:57:20 UTC
Add a dummy SUPPLY widget connected to the ASP that forces the chip registers to match the regmap cache when the ASP is powered-up. On a SoundWire system the ASP is free for use as a chip-to-chip interconnect. This can be either for the firmware on multiple CS35L56 to share reference audio; or as a bridge to another device. If it is a firmware interconnect it is owned by the firmware and the Linux driver should avoid writing the registers. However. If it is a bridge then Linux may take over and handle it as a normal codec-to-codec link. CS35L56 is designed for SDCA and a generic SDCA driver would know nothing about these chip-specific registers. So if the ASP is being used on a SoundWire system the firmware sets up the ASP registers. This means that we can't assume the default state of the ASP registers. But we don't know the initial state that the firmware set them to until after the firmware has been downloaded and booted, which can take several seconds when downloading multiple amps. To avoid blocking probe() for several seconds waiting for the firmware, the silicon defaults are assumed. This allows the machine driver to setup the ASP configuration during probe() without being blocked. If the ASP is hooked up and used, the SUPPLY widget ensures that the chip registers match what was configured in the regmap cache. If the machine driver does not hook up the ASP, it is assumed that it won't call any functions to configure the ASP DAI. Therefore the regmap cache will be clean for these registers so a regcache_sync() will not overwrite the chip registers. If the DAI is not hooked up, the dummy SUPPLY widget will not be invoked so it will never force-overwrite the chip registers. Backport note: This won't apply cleanly to kernels older than v6.6. Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com> Fixes: e49611252900 ("ASoC: cs35l56: Add driver for Cirrus Logic CS35L56") Link: https://msgid.link/r/20240129162737.497-8-rf@opensource.cirrus.com Signed-off-by: Mark Brown <broonie@kernel.org>
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.cocciconfig
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