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When HDA controller is resumed from suspend, i915 HDMI/DP codec requires that following order of actions is kept: - i915 display power up and configuration of link params - hda link reset and setup Current SOF HDA code delegates display codec power control to the codec driver. This works most of the time, but in runtime PM sequences, the above constraint may be violated. On platforms where BIOS values for HDA link parameters do not match hardware reset defaults, this may lead to errors in HDA verb transactions after resume. Fix the issue by explicitly powering the display codec in the HDA controller resume/suspend calls, thus ensuring correct ordering. Special handling is needed for the D0i3 flow, where display power must be turned off even though DSP is left powered. Now that we have more invocations of the display power helper functions, the conditional checks surrounding each call have been moved inside hda_codec_i915_display_power(). The two special cases of display powering at initial probe are handled separately. The intent is to avoid powering the display whenever no display codecs are used. Note that early powering of display was removed in commit687ae9e287("ASoC: intel: skl: Fix display power regression"). This change was also copied to the SOF driver. No failures have resulted as hardware default values for link parameters have worked out of the box. However with recent i915 driver changes like done in commit87c1694533("drm/i915: save AUD_FREQ_CNTRL state at audio domain suspend"), this does not hold anymore and errors are hit. Cc: Takashi Iwai <tiwai@suse.de> Signed-off-by: Kai Vehmanen <kai.vehmanen@linux.intel.com> Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com> Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com> Reviewed-by: Takashi Iwai <tiwai@suse.de> Link: https://lore.kernel.org/r/20200206200223.7715-2-kai.vehmanen@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.