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[178.39.53.103]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-395cb318a3dsm3503210f8f.74.2025.03.13.15.59.09 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 13 Mar 2025 15:59:09 -0700 (PDT) Message-ID: <990c38f8-0e7a-4e06-afa7-41d7c63bbc1e@gmail.com> Date: Thu, 13 Mar 2025 23:59:08 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 0/2] drm/msm/dp: Introduce link training per-segment for LTTPRs To: Stefan Schmidt Cc: Dmitry Baryshkov , linux-arm-msm@vger.kernel.org, dri-devel@lists.freedesktop.org, freedreno@lists.freedesktop.org, linux-kernel@vger.kernel.org, Rob Clark , Abhinav Kumar , Sean Paul , Marijn Suijten , David Airlie , Simona Vetter , laurentiu.tudor1@dell.com, abel.vesa@linaro.org, johan@kernel.org References: <20250311234109.136510-1-alex.vinarskis@gmail.com> Content-Language: en-US From: Aleksandrs Vinarskis In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 3/12/25 22:16, Stefan Schmidt wrote: > Hello Aleksandrs, > > On Wed, 12 Mar 2025 at 00:41, Aleksandrs Vinarskis > 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 > > Tested-by: Stefan Schmidt > > regards > Stefan Schmidt