On Wed, Apr 16, 2025 at 7:13 PM Aleksandrs Vinarskis <alex.vinars...@gmail.com> wrote: > > Recently added Initial LTTPR support in msm/dp has configured LTTPR(s) > to non-transparent mode to enable video output on X1E-based devices > that come with LTTPR on the motherboards. However, video would not work > if additional LTTPR(s) are present between sink and source, which is > the case for USB Type-C docks (eg. Dell WD19TB/WD22TB4), and at least > some universal Thunderbolt/USB Type-C monitors (eg. Dell U2725QE). > > First, take into account LTTPR capabilities when computing max link > rate, number of lanes. Take into account previous discussion on the > lists - exit early if reading DPCD caps failed. This also fixes > "*ERROR* panel edid read failed" on some monitors which seems to be > caused by msm_dp_panel_read_sink_caps running before LTTPR(s) are > initialized. > > Finally, implement link training per-segment. Pass lttpr_count to all > required helpers. > This seems to also partially improve UI (Wayland) hanging when > changing external display's link parameters (resolution, framerate): > * Prior to this series, via direct USB Type-C to display connection, > attempt to change resolution or framerate hangs the UI, setting does > not stick. Some back and forth replugging finally sets desired > parameters. > * With this series, via direct USB Type-C to display connection, > changing parameters works most of the time, without UI freezing. Via > docking station/multiple LTTPRs the setting again does not stick. > * On Xorg changing link paramaters works in all combinations. > > These appear to be mainlink initialization related, as in all cases LT > passes successfully. > > Test matrix: > * Dell XPS 9345, Ubuntu 24.10, Gnome 47, Wayland (myself) > * Left USB Type-C, Right USB Type-C > * Direct monitor connection, Dell WD19TB, Dell WD22TB4, USB > Type-C to HDMI dongle, USB Type-C to DP dongle > * Dell AW3423DWF, Samsung LS24A600, dual Samsung LS24A600 (one > monitor per USB Type-C connector) > * Dell XPS 9345, Ubuntu 24.10, Gnome 47, Wayland (myself) > * Left USB Type-C, Right USB Type-C > * Direct monitor connection > * Samsung S34BG85 (USB Type-C), Dell U2725QE (universal > Thunderbolt/USB Type-C, probes with an LTTPR when in USB > Type-C/DP Alt mode) > * Dell XPS 9345, Debian trixie/sid, Gnome 48, Wayland (Stefan Schmidt) > * Left USB Type-C, Right USB Type-C > * Dell WD15 Dock with DisplayPort connected > * Dell HD22Q dock with HDMI connected > * USB Type-C to HDMI dongle > * Dell U3417W
For the series, Tested-by: Rob Clark <robdcl...@gmail.com> # yoga slim 7x patch 4/4 had a number of conflicting hunks, you might need to rebase on msm-next BR, -R > In both cases, "Thunderbot Support"/"USB4 PCIE Tunneling" was disabled > in UEFI to force universal Thunderbolt/USB Type-C devices to work in > DP Alt mode. > In both cases laptops had HBR3 patches applied [1], resulting in > maximum successful link at 3440x1440@100hz and 4k@60hz respectively. > When using Dell WD22TB4/U2725QE, USB Type-C pin assigment D got enabled > and USB3.0 devices were working in parallel to video ouput. > > Known issues: > * As mentioned above, it appears that on Gnome+Wayland framerate and > resolution parameter adjustment is not stable. > > Due to lack of access to the official DisplayPort specfication, changes > were primarily inspired by/reverse engineered from Intel's i915 driver. > > [1] > https://lore.kernel.org/all/20250226231436.16138-2-alex.vinars...@gmail.com/ > > Signed-off-by: Aleksandrs Vinarskis <alex.vinars...@gmail.com> > > --- > > Changes in v3: > - Split 1st patch into 3 > - Simplified handling of max_lttpr_lanes/max_lttpr_rate > - Moved lttpr_common_caps to msm_dp_link (not msm_dp_panel, as LTTPRs > are link related, not panel related) > - Picked Stefan's T-b tag (last patch only, as 1st one is getting split) > - Droped Abel's R-b tags from 1st patch that got split due to high diff > - Fixed alignment issues, initialization of variables, debug prints > - Moved lttpr_count to avoid ugly pointer > - Link to v2: > https://lore.kernel.org/all/20250311234109.136510-1-alex.vinars...@gmail.com/ > > Changes in v2: > - Picked up Abel's R-b tags > - Fixed typo as per Abel, fixed readability as per Johan > - Updated cover and commit message on mailink issue which appears to be > specific to Gnome+Wayland. No problems on Xorg. > - Link to v1: > https://lore.kernel.org/all/20250310211039.29843-1-alex.vinars...@gmail.com/ > > Aleksandrs Vinarskis (4): > drm/msm/dp: Fix support of LTTPR initialization > drm/msm/dp: Account for LTTPRs capabilities > drm/msm/dp: Prepare for link training per-segment for LTTPRs > drm/msm/dp: Introduce link training per-segment for LTTPRs > > drivers/gpu/drm/msm/dp/dp_ctrl.c | 126 ++++++++++++++++++++-------- > drivers/gpu/drm/msm/dp/dp_display.c | 27 ++++-- > drivers/gpu/drm/msm/dp/dp_link.h | 4 + > drivers/gpu/drm/msm/dp/dp_panel.c | 12 ++- > 4 files changed, 122 insertions(+), 47 deletions(-) > > -- > 2.45.2 >
