SRU: https://lists.ubuntu.com/archives/kernel-
team/2020-November/114986.html (unstable & oem-5.10)
** Changed in: linux-oem-5.10 (Ubuntu Focal)
Importance: Undecided => High
** Changed in: linux-oem-5.10 (Ubuntu Focal)
Status: New => In Progress
** Changed in: linux-oem-5.10 (Ubuntu Focal)
Assignee: (unassigned) => You-Sheng Yang (vicamo)
** Changed in: linux (Ubuntu Focal)
Status: New => Invalid
** Description changed:
+ [SRU Justification]
+
+ [Impact]
+
+ On platforms supported DP tunneling over USB 3.2 or so, a Retimer is
+ required on the host side to cover insertion loss. On such platforms the
+ rtimer firmware maybe configured to use LTTPR (Link Training Tunable PHY
+ Repeater) non-transparent mode only, which is only supported in drm-tip
+ currently. Without LTTPR support, link training may fail with following
+ error messages depending on the data path configuration:
+
+ i915 0000:00:02.0: [drm] *ERROR* Link Training Unsuccessful
+ i915 0000:00:02.0: [drm] *ERROR* CPU pipe A FIFO underrun
+
+ [Fix]
+
+ Patchset https://www.spinics.net/lists/intel-gfx/msg248700.html
+ ("drm/i915: Add support for LTTPR non-transparent link training mode")
+ is required to fix this issue. It has been landed to drm-tip and will
+ only included to mainline in v5.11.
+
+ Patchset https://patchwork.freedesktop.org/series/76993/ ("Plumb crtc
+ state to link training code") is included for link training functions
+ prototype changes.
+
+ [Test Case]
+
+ On Dell OptiPlex and WD19 docking station, use following steps to verify:
+ 1. disconnect WD19 from OptiPlex, disconnect OptiPlex's power
+ 2. attach OptiPlex's power cord
+ 3. attach WD19's power cord
+ 4. attach DP to WD19
+ 5. attach WD19 to OptiPlex
+ 6. boot up and check if boot to GUI directly
+ 7. `dmesg` and check if aforementioned DRM link training error appears
+
+ [Regression Potential]
+
+ The second patchset pulled for dependency doesn't have too much
+ effective changes but refactoring some translation functions, so very
+ unlikely to have regressions.
+
+ For the major part, LTTPR support, when LTTPR is either not detected or
+ not supported, it will fall back to use transparent mode as it was.
+ Otherwise, DP Standard recommends to use LTTPR non-transparent mode for
+ link training, so this should be the right way to have best hardware
+ support.
+
+ ========== original bug description ==========
+
[Summary]
When the monitor ONLY is connected to the WD19 (DP port) and WD19 is
connected to the type c port than boot the machine, the monitor shows no video
output after loaded i915.
[Reproduce Steps]
1. connect power cable of WD19
2. connect DP cable from monitor to WD19
3. connect power cable to target system.
4. connect type c cable from WD19 to target system
5. boot up
[Results]
Expected: video output as there is only one monitor connected.
Actual: No video output.
ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: linux-image-5.6.0-1033-oem 5.6.0-1033.35
ProcVersionSignature: Ubuntu 5.6.0-1033.35-oem 5.6.19
Uname: Linux 5.6.0-1033-oem x86_64
ApportVersion: 2.20.11-0ubuntu27.11
Architecture: amd64
CasperMD5CheckResult: skip
Date: Thu Nov 12 05:11:11 2020
DistributionChannelDescriptor:
- # This is the distribution channel descriptor for the OEM CDs
- # For more information see
http://wiki.ubuntu.com/DistributionChannelDescriptor
- canonical-oem-somerville-focal-amd64-20200502-85+fossa-metapod+X40
+ # This is the distribution channel descriptor for the OEM CDs
+ # For more information see
http://wiki.ubuntu.com/DistributionChannelDescriptor
+ canonical-oem-somerville-focal-amd64-20200502-85+fossa-metapod+X40
InstallationDate: Installed on 2020-11-03 (9 days ago)
InstallationMedia: Ubuntu 20.04 "Focal" - Build amd64 LIVE Binary
20200502-05:58
SourcePackage: linux-signed-oem-5.6
UpgradeStatus: No upgrade log present (probably fresh install)
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https://bugs.launchpad.net/bugs/1903969
Title:
failed to boot to GUI: i915 0000:00:02.0: [drm] *ERROR* Link Training
Unsuccessful
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