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commitc2c3657f0aupstream. It's been reported that, when neither nouveau nor Nvidia graphics driver is used, the screen starts flickering. And, after comparing between the working case (stable 4.4.x) and the broken case, it turned out that the problem comes from the audio component binding. The Nvidia and AMD audio binding code clears the bus->keep_power flag whenever snd_hdac_acomp_init() succeeds. But this doesn't mean that the component is actually bound, but it merely indicates that it's ready for binding. So, when both nouveau and Nvidia are blacklisted or not ready, the driver keeps running without the audio component but also with bus->keep_power = false. This made the driver runtime PM kicked in and powering down when unused, which results in flickering in the graphics side, as it seems. For fixing the bug, this patch moves the bus->keep_power flag change into generic_acomp_notifier_set() that is the function called from the master_bind callback of component ops; i.e. it's guaranteed that the binding succeeded. BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=208609 Fixes:5a858e79c9("ALSA: hda - Disable audio component for legacy Nvidia HDMI codecs") Cc: <stable@vger.kernel.org> Link: https://lore.kernel.org/r/20200728082033.23933-1-tiwai@suse.de Signed-off-by: Takashi Iwai <tiwai@suse.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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.