64e62bdf04
[Why] This patch is trying to address the issue observed when hotplug DP daisy chain monitors. e.g. src-mstb-mstb-sst -> src (unplug) mstb-mstb-sst -> src-mstb-mstb-sst (plug in again) Once unplug a DP MST capable device, driver will call drm_dp_mst_topology_mgr_set_mst() to disable MST. In this function, it cleans data of topology manager while disabling mst_state. However, it doesn't clean up the proposed_vcpis of topology manager. If proposed_vcpi is not reset, once plug in MST daisy chain monitors later, code will fail at checking port validation while trying to allocate payloads. When MST capable device is plugged in again and try to allocate payloads by calling drm_dp_update_payload_part1(), this function will iterate over all proposed virtual channels to see if any proposed VCPI's num_slots is greater than 0. If any proposed VCPI's num_slots is greater than 0 and the port which the specific virtual channel directed to is not in the topology, code then fails at the port validation. Since there are stale VCPI allocations from the previous topology enablement in proposed_vcpi[], code will fail at port validation and reurn EINVAL. [How] Clean up the data of stale proposed_vcpi[] and reset mgr->proposed_vcpis to NULL while disabling mst in drm_dp_mst_topology_mgr_set_mst(). Changes since v1: *Add on more details in commit message to describe the issue which the patch is trying to fix Signed-off-by: Wayne Lin <Wayne.Lin@amd.com> [added cc to stable] Signed-off-by: Lyude Paul <lyude@redhat.com> Link: https://patchwork.freedesktop.org/patch/msgid/20191205090043.7580-1-Wayne.Lin@amd.com Cc: <stable@vger.kernel.org> # v3.17+ |
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README
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.