drivers/gpu/drm/msm/dp/dp_ctrl.c | 137 +++++++++++++++++++--------- drivers/gpu/drm/msm/dp/dp_ctrl.h | 2 +- drivers/gpu/drm/msm/dp/dp_display.c | 31 +++++-- drivers/gpu/drm/msm/dp/dp_panel.c | 30 ++++-- drivers/gpu/drm/msm/dp/dp_panel.h | 2 + 5 files changed, 141 insertions(+), 61 deletions(-)
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
* 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
* 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)
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.vinarskis@gmail.com/
Signed-off-by: Aleksandrs Vinarskis <alex.vinarskis@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.vinarskis@gmail.com/
---
Aleksandrs Vinarskis (2):
drm/msm/dp: Fix support of LTTPR handling
drm/msm/dp: Introduce link training per-segment for LTTPRs
drivers/gpu/drm/msm/dp/dp_ctrl.c | 137 +++++++++++++++++++---------
drivers/gpu/drm/msm/dp/dp_ctrl.h | 2 +-
drivers/gpu/drm/msm/dp/dp_display.c | 31 +++++--
drivers/gpu/drm/msm/dp/dp_panel.c | 30 ++++--
drivers/gpu/drm/msm/dp/dp_panel.h | 2 +
5 files changed, 141 insertions(+), 61 deletions(-)
--
2.45.2
Hello Aleksandrs,
On Wed, 12 Mar 2025 at 00:41, Aleksandrs Vinarskis
<alex.vinarskis@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
> * 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
> * 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)
You can add the following:
* Dell XPS 9345, Debian trixie/sid, Gnome 48, Wayland
* 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
> 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.
I can confirm this on Gnome 48 + Wayland as well. Sometimes the resolution
change from gnome settings gets stuck and does not apply. It normally works
here around every third try or so when using a dock.
> 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.vinarskis@gmail.com/
>
> Signed-off-by: Aleksandrs Vinarskis <alex.vinarskis@gmail.com>
Tested-by: Stefan Schmidt <stefan.schmidt@linaro.org>
regards
Stefan Schmidt
On 3/12/25 22:16, Stefan Schmidt wrote: > Hello Aleksandrs, > > On Wed, 12 Mar 2025 at 00:41, Aleksandrs Vinarskis > <alex.vinarskis@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 >> * 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 >> * 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) > > You can add the following: > * Dell XPS 9345, Debian trixie/sid, Gnome 48, Wayland > * 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 Hi, Thanks for testing, will add on next re-spin. > >> 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. > > I can confirm this on Gnome 48 + Wayland as well. Sometimes the resolution > change from gnome settings gets stuck and does not apply. It normally works > here around every third try or so when using a dock. Good to know that it isn't issue only on my side :) Alex > >> 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.vinarskis@gmail.com/ >> >> Signed-off-by: Aleksandrs Vinarskis <alex.vinarskis@gmail.com> > > Tested-by: Stefan Schmidt <stefan.schmidt@linaro.org> > > regards > Stefan Schmidt
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