[SRU][Q/R][PATCH 0/1] Could not output video from type-c to VGA adapter

[AceLan Kao]

From: "Chia-Lin Kao (AceLan)" <acelan.kao at canonical.com>

BugLink: https://bugs.launchpad.net/bugs/2133143

[Impact]
Plugged the Lenovo USB-C to VGA adapter or Dell DA310 hub to thunderbolt 5
port, the communication through AUX timed out, and there is no video
output to the VGA monitor

i915 0000:00:02.0: [drm:drm_dp_dpcd_read [drm_display_helper]] AUX USBC4/DDI TC4/PHY TC4: 0x00000 AUX -> (ret=-110)

[Fix]
https://lkml.org/lkml/2025/11/27/193
v2 - https://lore.kernel.org/lkml/20251204024647.1462866-1-acelan.kao@canonical.com/T/#u

[Test]
1. Find a device with TB5 port
2. Plug a VGA monitor to Lenovo USB-C to VGA adapter[17ef:7217] or Dell DA310[413c:c010]
3. Plug the adapter/hub to the TB5 port
4. The external monitor should work as expected.

[Where problems could occur]
It handles the fail case and doesn't affect the code path if it already works. No regression.

Chia-Lin Kao (AceLan) (1):
  UBUNTU: SAUCE: drm/dp: Add byte-by-byte fallback for broken USB-C
    adapters

 include/drm/display/drm_dp_helper.h | 57 +++++++++++++++++++----------
 1 file changed, 37 insertions(+), 20 deletions(-)

-- 
2.43.0