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commit c366b3dbbab14b28d044b94eb9ce77c23482ea35 upstream. Klaus Ethgen reported occasional high CPU usages in his system that seem caused by HD-audio driver. The perf output revealed that it's in the unsolicited event handling in the workqueue, and the problem seems triggered by some communication stall between the controller and the codec at the runtime or system resume. Actually a similar phenomenon was seen in the past for other Intel platforms, and we already applied the workaround to enforce sync-write for CORB/RIRB verbs for Skylake and newer chipsets (commit 2756d9143aa5 "ALSA: hda - Fix intermittent CORB/RIRB stall on Intel chips"). Fortunately, the same workaround is applicable to the old chipset, and the experiment showed the positive effect. Based on the experiment result, this patch enables the sync-write workaround for all Intel chipsets. The only reason I hesitated to apply this workaround was about the possibly slightly higher CPU usage. But if the lack of sync causes a much severer problem even for quite old chip, we should think this would be necessary for all Intel chips. Reported-by: Klaus Ethgen <Klaus@ethgen.ch> Cc: <stable@vger.kernel.org> Link: https://lore.kernel.org/r/20191223171833.GA17053@chua Link: https://lore.kernel.org/r/20191223221816.32572-1-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.