Public bug reported:
[Impact]
1. Connect the K2 Dock to the Host. Plug in two 4K@60Hz monitors to the dock
(including one Thunderbolt monitor connected at the end). The Thunderbolt
monitor cannot achieve 4K@60Hz and is limited to 4K@30Hz.
2. Connect the K2 Dock to the SUT and plug in a 5K@120Hz monitor. The refresh
rate is limited to 60Hz.
[Fix]
Applied below series of patch in linux-next fix the issue.
f2e2092a979c drm/i915/display: Use joined pipes in dsc helpers for slices, bpp
f87bdbd66de4 drm/i915/display: Use joined pipes in
intel_mode_valid_max_plane_size
d09568137344 drm/i915/display: Use joined pipes in intel_dp_joiner_needs_dsc
eb920fbbb4c8 drm/i915/display: Simplify intel_joiner_num_pipes and its usage
26fee9e09be3 drm/i915/display: Check whether platform supports joiner
[Test]
1. connect 2 4k@60Hz monitors to the dock and check the refresh rate of both
monitor are at 60Hz
2. or connect one 5k@120Hz monitor to the dock and check the refresh rate is at
120Hz
[Where problems could occur]
The series of patches fix the calculation of the num_joined_pipes, it should
provide a more accurate bandwidth value. The worse case could lead to blank
screen or downgrade the refresh rate.
** Affects: linux-oem-6.11 (Ubuntu)
Importance: Undecided
Status: New
** Affects: linux-oem-6.11 (Ubuntu Noble)
Importance: Undecided
Status: New
** Also affects: linux-oem-6.11 (Ubuntu Noble)
Importance: Undecided
Status: New
** Description changed:
[Impact]
1. Connect the K2 Dock to the Host. Plug in two 4K@60Hz monitors to the dock
(including one Thunderbolt monitor connected at the end). The Thunderbolt
monitor cannot achieve 4K@60Hz and is limited to 4K@30Hz.
2. Connect the K2 Dock to the SUT and plug in a 5K@120Hz monitor. The refresh
rate is limited to 60Hz.
[Fix]
- Applied below series of patch fix the issue.
+ Applied below series of patch in linux-next fix the issue.
f2e2092a979c drm/i915/display: Use joined pipes in dsc helpers for slices, bpp
f87bdbd66de4 drm/i915/display: Use joined pipes in
intel_mode_valid_max_plane_size
d09568137344 drm/i915/display: Use joined pipes in intel_dp_joiner_needs_dsc
eb920fbbb4c8 drm/i915/display: Simplify intel_joiner_num_pipes and its usage
26fee9e09be3 drm/i915/display: Check whether platform supports joiner
[Test]
1. connect 2 4k@60Hz monitors to the dock and check the refresh rate of both
monitor are at 60Hz
2. or connect one 5k@120Hz monitor to the dock and check the refresh rate is
at 120Hz
[Where problems could occur]
The series of patches fix the calculation of the num_joined_pipes, it should
provide a more accurate bandwidth value. The worse case could lead to blank
screen or downgrade the refresh rate.
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https://bugs.launchpad.net/bugs/2088972
Title:
DP/MST Bandwidth issue when connect dual 4k@60Hz or 5k@120Hz on a dock
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