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Add helpers to program SPA/CPA bits, using a mutex to access the shared LCTL register if required. All links are managed with the same LCTLx.SPA bits. However there are quite a few implementation details to be aware of: Legacy HDaudio multi-links are powered-up when exiting reset, which requires the ref_count to be manually set to one when initializing the link. Alternate links for SoundWire/DMIC/SSP need to be explicitly powered-up before accessing the SHIM/IP/Vendor-Specific SHIM space for each sublink. DMIC/SSP/SoundWire are all different cases with a different device/dai/hlink relationship. SoundWire will handle power management with the auxiliary device resume/suspend routine. The ref_count is not necessary in this case. The DMIC/SSP will by contrast handle the power management from DAI .startup and .shutdown callbacks. The SSP has a 1:1 mapping between sublink and DAI, but it's bidirectional so the ref_count will help avoid turning off the sublink when one of the two directions is still in use. The DMIC has a single link but two DAIs for data generated at different sampling frequencies, again the ref_count will make sure the two DAIs can be used concurrently. And last the SoundWire Intel require power-up/down and bank switch to be handled with a lock already taken, so the 'eml_lock' is made optional with the _unlocked versions of the helpers. Note that the _check_power_active() implementation is similar to previous helpers in sound/hda/ext, with sleep duration and timeout aligned with hardware recommendations. If desired, this helper could be modified in a second step with .e.g. readl_poll_timeout() Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com> Reviewed-by: Rander Wang <rander.wang@intel.com> Reviewed-by: Péter Ujfalusi <peter.ujfalusi@linux.intel.com> Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com> Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com> Reviewed-by: Takashi Iwai <tiwai@suse.de> Link: https://lore.kernel.org/r/20230404104127.5629-9-peter.ujfalusi@linux.intel.com Signed-off-by: Mark Brown <broonie@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.