[Bug 2131066] Re: No output on external monitor when connecting to dell dock

** Changed in: linux (Ubuntu Questing)
Status: In Progress => Fix Committed

** Changed in: linux (Ubuntu Questing)
Assignee: AceLan Kao (acelankao) => Edoardo Canepa (ecanepa)

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https://bugs.launchpad.net/bugs/2131066

Title:
No output on external monitor when connecting to dell dock

Status in HWE Next:
New
Status in linux package in Ubuntu:
In Progress
Status in linux-oem-6.14 package in Ubuntu:
Invalid
Status in linux-oem-6.17 package in Ubuntu:
Invalid
Status in linux source package in Noble:
Won't Fix
Status in linux-oem-6.14 source package in Noble:
Fix Released
Status in linux-oem-6.17 source package in Noble:
Fix Released
Status in linux source package in Questing:
Fix Committed
Status in linux-oem-6.14 source package in Questing:
Invalid
Status in linux-oem-6.17 source package in Questing:
Invalid
Status in linux source package in Resolute:
In Progress
Status in linux-oem-6.14 source package in Resolute:
Invalid
Status in linux-oem-6.17 source package in Resolute:
Invalid

Bug description:
[Impact]
The 4k monitor on the dock is blank when connected to the device.

[Fix]
Intel provides a patch series to address this issue. The patches include
fixes for Display Stream Compression (DSC) and Panel Self Refresh (PSR).
One of the key changes refines a workaround for a PSR underrun issue,
ensuring it is only applied under the correct conditions to prevent
display problems on MST setups.
https://patchwork.freedesktop.org/patch/686338/

c390bf07961b drm/i915/dp: Fix panel replay when DSC is enabled
470b84af457e drm/i915/dp_mst: Recompute all MST link CRTCs if DSC gets enabled on the link
7c027070e98d drm/i915/dp_mst: Track DSC enabled status on the MST link
b762ae48293e drm/i915/dp_mst: Reuse the DP-SST helper function to compute FEC config
cb6c8f1f6f46 drm/i915/dp: Export helper to determine if FEC on non-UHBR links is required
69df31263bca drm/i915/dp: Ensure the FEC state stays disabled for UHBR links
c88e70dc8bfc drm/i915/dsc: Add helper to enable the DSC configuration for a CRTC

[Test]
1. Boot to OS, connect dell dock
2. Connect 4k monitor to dock, it should always work.

[Where problems could occur]
This series of patches touches advanced features in the Intel graphics
driver, including Display Stream Compression (DSC), Panel Self Refresh (PSR),
and Forward Error Correction (FEC), especially for DisplayPort Multi-Stream
Transport (MST). Due to the complexity of these features, regressions
could manifest in the following ways:

- Flickering, link training failures (resulting in a blank screen), or other
visual corruption. These issues might occur with specific monitors or docks,
especially when using high resolutions or refresh rates.

- The disabling of PSR for monitors on an MST link is a key part of the fix,
which will lead to increased power consumption in those configurations.

- While aiming to fix a specific problem with a Dell dock, the changes could
inadvertently affect other hardware configurations that were previously
working correctly, leading to regressions on different docks or monitors.

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