[adding a few people and lists to the recipients] Hi! Thx for your rpeort. On 27.07.24 18:07, kevin@xxxxxxxx wrote: > Connecting two 4k displays with display port through a lenovo usb-c > dock (type 40AS) to a Lenovo P14s Gen 2 (type 21A0) results in no > image on the connected displays. > > The CPU in the Lenovo P14s is a 'AMD Ryzen 7 PRO 5850U with Radeon > Graphics' and it has no discrete GPU. > > I first noticed the issue with kernel version '6.10.0-arch1-2' > provided by arch linux. With the previous kernel version > '6.9.10.arch1-1' both connected displays worked normally. I reported > the issue in the arch forums at > https://bbs.archlinux.org/viewtopic.php?id=297999 and was guided to > do a bisection to find the commit that caused the problem. Through > testing I identified that the issue is not present in the latest > kernel directly compiled from the trovalds/linux git repository. > > With git bisect I identified 4df96ba66760345471a85ef7bb29e1cd4e956057 That's 4df96ba6676034 ("drm/amd/display: Add timing pixel encoding for mst mode validation") [v6.10-rc1] from Hersen Wu. Did you try if reverting that commit is possible and might fix the problem? > as the first bad commit and fa57924c76d995e87ca3533ec60d1d5e55769a27 That's fa57924c76d995 ("drm/amd/display: Refactor function dm_dp_mst_is_port_support_mode()") [v6.10-post] from Wayne Lin. > as the first commit that fixed the problem again. Hmm, the latter commit does not have a fixes tag and might or might not be to invasive to backport to 6.10. Let's see what the AMD developers say. > The initial commit only still shows an image on one of the connected > 4k screens. I have not investigated further to find out at what point > both displays stopped showing an image. Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat) -- Everything you wanna know about Linux kernel regression tracking: https://linux-regtracking.leemhuis.info/about/#tldr If I did something stupid, please tell me, as explained on that page.
