8e794421bc
[Why]
Currently, we will try to get dm.dc_lock in handle_hpd_rx_irq() when
link lost happened, which is risky and could cause deadlock.
e.g. If we are under procedure to enable MST streams and then monitor
happens to toggle short hpd to notify link lost, then
handle_hpd_rx_irq() will get blocked due to stream enabling flow has
dc_lock. However, under MST, enabling streams involves communication
with remote sinks which need to use handle_hpd_rx_irq() to handle
sideband messages. Thus, we have deadlock here.
[How]
Target is to have handle_hpd_rx_irq() finished as soon as possilble.
Hence we can react to interrupt quickly. Besides, we should avoid to
grabe dm.dc_lock within handle_hpd_rx_irq() to avoid deadlock situation.
Firstly, revert patches which introduced to use dm.dc_lock in
handle_hpd_rx_irq():
* commit ("drm/amd/display: NULL pointer error during ")
* commit ("drm/amd/display: Only one display lights up while using MST")
* commit ("drm/amd/display: take dc_lock in short pulse handler only")
Instead, create work to handle irq events which needs dm.dc_lock.
Besides:
* Create struct hpd_rx_irq_offload_work_queue for each link to handle
its short hpd events
* Avoid to handle link lost/ automated test if the link is disconnected
* Defer dc_lock needed works in dc_link_handle_hpd_rx_irq(). This
function should just handle simple stuff for us (e.g. DPCD R/W).
However, deferred works should still be handled by the order that
dc_link_handle_hpd_rx_irq() used to be.
* Change function name dm_handle_hpd_rx_irq() to
dm_handle_mst_sideband_msg() to be more specific
Reviewed-by: Nicholas Kazlauskas <Nicholas.Kazlauskas@amd.com>
Acked-by: Mikita Lipski <mikita.lipski@amd.com>
Signed-off-by: Wayne Lin <Wayne.Lin@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.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.