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The i915 display power is requested both by controller (for init and link reset) as well as by codec driver (for codec control). There's an additional constraint that on some platforms frequent changes to display power state may cause visible flicker. To avoid this, the SOF hda controller requests display power whenever it is active and only releases it when runtime suspended. This patch utilizes the new hdac_bus link_power op to plug into HDA link state changes. By monitoring link state changes, we can keep the controller side display power wakeref until the codec driver has completed its work, and only release the wakeref when codec driver is suspended. Signed-off-by: Kai Vehmanen <kai.vehmanen@linux.intel.com> Acked-by: Mark Brown <broonie@kernel.org> Link: https://lore.kernel.org/r/20210205184630.1938761-4-kai.vehmanen@linux.intel.com Signed-off-by: Takashi Iwai <tiwai@suse.de>
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.