https://bugzilla.kernel.org/show_bug.cgi?id=208947
Bug ID: 208947 Summary: amdgpu DisplayPort won't recognize all display modes after 5.9 merges Product: Drivers Version: 2.5 Kernel Version: 5.9 staging-testing, rc1, and latest linux.git Hardware: x86-64 OS: Linux Tree: Mainline Status: NEW Severity: normal Priority: P1 Component: Video(DRI - non Intel) Assignee: drivers_video-dri@kernel-bugs.osdl.org Reporter: ckane@colemankane.org Regression: No
I've got an AMD Ryzen 7 1700 and a POLARIS10 Radeon RX 580M GPU in an ASUS ROG GL702ZC laptop.
I'm using the regular 5.8.1 kernel on Arch linux, and also have been tracking in-development kernel changes via the "staging-testing" branch on the gregkh/staging.git Linux tree as well as the torvalds/linux.git tree.
Sometime during the course of the 5.9 updates getting merged into those trees, the 5.9 kernels I build no longer recognize all of the graphics modes for my 4K (3840x2160) monitor when it is plugged into the DisplayPort. Instead, the highest mode reported available is 1024x768, and Xorg also gets limited to these choices.
This behavior appears limited to the monitor being plugged in via its DisplayPort input. When I use an HDMI input, all of the supported graphics modes are reported properly. I am using /sys/class/drm/card0-DP-1/modes to display the available modes, and also starting Xorg to test it as well.
Would be happy to test patches if this is a known regression, or would appreciate some help/direction in tracking down potential likely culprits of the problem so I can try to diagnose it myself. I am somewhat familiar with kernel development, so I'm capable of hacking on it a bit if anyone can point me in a good direction. I'm just not too familiar with the inner workings of the AMDGPU, KMS, or DRM code. Not even certain if this is an issue specific to AMDGPU or something agnostic to the specific video hw.
I also tried dumping the /sys/class/drm/card0-DP-1/edid after booting into 5.8.1 and then 5.9-latest and I get exactly the same data for both, so it seems like the EDID data is at least being fetched properly. I also tried saving that EDID data to a *.bin file and manually loading that via kernel arguments (drm.edid_firmware): verified it was loading properly for DP-1, but I still got the same results (no high-resolution video modes).
Let me know what data would be helpful to attach to this issue, as well.
Thanks, Coleman Kane