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During the card registration, transactions on the SoundWire bus can be initiated. If the ALSA card is registered after the bus suspends, timeouts can be seen while reading/writing codec registers. This is extremely easy to reproduce in driver bind/unbind tests. In an initial experiment, the ASoC soc-component.c code was modified to initiate a pm_runtime resume on a component probe. The results showed this was too invasive. Instead this patch suggests resuming the SoundWire component only. Because of the parent-child hierarchy enforced by the pm_runtime framework, it can be argued that the codec component probe should be enough to resume all necessary devices, and indeed the same resume will be applied to SoundWire codecs used on Intel platforms. Calling pm_runtime_resume() on both the Intel and codec sides has the benefit of resuming the bus without assuming any order during the card registration. The first component on a dailink to be probed will resume the bus. In addition, if a codec driver did not implement this transition, the Intel component would still resume the bus and avoid timeouts on card registration. BugLink: https://github.com/thesofproject/linux/issues/3651 Reviewed-by: Rander Wang <rander.wang@intel.com> Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com> Reviewed-by: Bard Liao <yung-chuan.liao@linux.intel.com> Reviewed-by: Péter Ujfalusi <peter.ujfalusi@linux.intel.com> Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com> Link: https://lore.kernel.org/r/20220621225641.221170-4-pierre-louis.bossart@linux.intel.com Signed-off-by: Vinod Koul <vkoul@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.