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In some cases the sink can reset itself after it was configured into MST mode, without the driver noticing the disconnected state. For instance the reset may happen in the middle of a modeset, or the (long) HPD pulse generated may be not long enough for the encoder detect handler to observe the HPD's deasserted state. In this case the sink's DPCD register programmed to enable MST will be reset, while the driver still assumes MST is still enabled. Detect this condition, which will tear down and recreate/re-enable the MST topology. v2: - Add a code comment about adjusting the expected DP_MSTM_CTRL register value for SST + SideBand. (Suraj, Jani) - Print a debug message about detecting the link reset. (Jani) - Verify the DPCD MST state only if it wasn't already determined that the sink is disconnected. Cc: stable@vger.kernel.org Cc: Jani Nikula <jani.nikula@intel.com> Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/11195 Reviewed-by: Suraj Kandpal <suraj.kandpal@intel.com> (v1) Signed-off-by: Imre Deak <imre.deak@intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20240823162918.1211875-1-imre.deak@intel.com (cherry picked from commit 594cf78dc36f31c0c7e0de4567e644f406d46bae) Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.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 reStructuredText 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.