https://bugs.freedesktop.org/show_bug.cgi?id=102985
Bug ID: 102985 Summary: HDMI 2.0 4k EDIDs not available (Radeon RX Vega 56) Product: DRI Version: DRI git Hardware: x86-64 (AMD64) OS: Linux (All) Status: NEW Severity: normal Priority: medium Component: DRM/AMDgpu Assignee: dri-devel@lists.freedesktop.org Reporter: bicom@invergo.net
Created attachment 134476 --> https://bugs.freedesktop.org/attachment.cgi?id=134476&action=edit DRM/AMDGPU logs (journalctl)
I have a Radeon RX Vega 56 connected to a Sony 4K TV (kd-49x8305c) via a "Premium" (certified) HDMI 2.0 cable. The TV's HDMI input is set to "Enhanced Format". Thus, on the hardware side, everything's ready to go for 4k@60Hz. On the software side, I'm running Arch Linux with mesa-git (rev. 066d1dc951), llvm-svn (rev. 313470), and Linux branch amd-staging-drm-next (4.13 rev. dcae401d1113). I'm running Gnome and I've tested both Wayland and Xorg.
While other functionality such as rendering and acceleration work with this setup, I have been unable to access any 4k resolutions.
As you'll see in the attached logs, the maximum resolution detected from the TV's EDID is 1920x1080. However, using the program edid-decode (output attached), one can see that the EDID clearly advertises 4k modes, however, they're in the Extension block at VIC indexes higher than 64.
Until recently, 64 was the highest supported by drivers/gpu/drm/drm_edid.c in the kernel. However, that has been fixed:
https://github.com/torvalds/linux/commit/8ec6e0755565192b328059b64f982adabbe...
That commit has been merged into the amd-staging-drm-next kernel (but not amd-staging), and the revision that I have built and installed includes that code. Nevertheless, I haven't had any luck in getting the computer to recognize any of those extended modes.
I have tried adding the mode manually via xrandr, however when I try to switch to that mode, I get the error "xrandr: Configure crtc 0 failed". Trying to set it in a conf file in /etc/X11/xorg.conf.d also didn't work (I no longer have a configuration file in there). I've also tried forcing it from the kernel command line (video=3840x2160@60) to no avail. Still, all of those seem like workarounds when I think the problem is pretty clearly that the VIC 65+ modes are not detected.