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d74408f528
Our SDVO audio support is pretty bogus. We can't push audio over the SDVO bus, so trying to enable audio in the SDVO control register doesn't do anything. In fact it looks like the SDVO encoder will always mix in the audio coming over HDA, and there's no (at least documented) way to disable that from our side. So HDMI audio does work currently on gen4 but only by luck really. On gen3 it got broken by the referenced commit. And what has always been missing on every platform is the ELD. To pass the ELD to the audio driver we need to write it to magic buffer in the SDVO encoder hardware which then gets pulled out via HDA in the other end. Ie. pretty much the same thing we had for native HDMI before we started to just pass the ELD between the drivers. This sort of explains why we even have that silly hardware buffer with native HDMI. $ cat /proc/asound/card0/eld#1.0 -monitor_present 0 -eld_valid 0 +monitor_present 1 +eld_valid 1 +monitor_name LG TV +connection_type HDMI +... This also fixes our state readout since we can now query the SDVO encoder about the state of the "ELD valid" and "presence detect" bits. As mentioned those don't actually control whether audio gets sent over the HDMI cable, but it's the best we can do. And with the state checker appeased we can re-enable HDMI audio for gen3. Cc: stable@vger.kernel.org Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: zardam@gmail.com Tested-by: zardam@gmail.com Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=108976 Fixes: de44e256b92c ("drm/i915/sdvo: Shut up state checker with hdmi cards on gen3") Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20190409144054.24561-3-ville.syrjala@linux.intel.com Reviewed-by: Imre Deak <imre.deak@intel.com> (cherry picked from commit dc49a56bd43bb04982e64b44436831da801d0237) Signed-off-by: Jani Nikula <jani.nikula@intel.com>
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.