On Mon, 16 Mar 2026 09:42:32 +0100, Julian Wollrath wrote: > when turning the display off via 'xset dpms force off' I observe the > following warning and trace under 7.0-rc4 with a AMD Ryzen 7 PRO 8840U
I can reproduce the same warning on different hardware with a different trigger. Machine: HP Z66 G6 14 (ProBook 4 G1ah), AMD Ryzen 7 H 255 (HawkPoint1), kernel 7.0.8-200.fc44.x86_64. Trigger: HDMI hotplug with an external 4K monitor. The Z66's HDMI port uses a DP-to-HDMI protocol converter with FRL support (dmesg shows "DP-HDMI FRL PCON supported"). Connecting the monitor at boot causes the first timeout during initialization; subsequent hotplug events repeat it at runtime. The call trace matches yours exactly: dcn31_program_compbuf_size line:141 dcn20_optimize_bandwidth dc_commit_state_no_check dc_commit_streams amdgpu_dm_atomic_commit_tail Not seen with 6.19.x. CachyOS community bisected this to: commit 592c5b80110d5e9e50873b5364818cb6f401e26d "drm/amd/display: Migrate HUBBUB register access from hwseq to hubbub component" One thing I noticed on my setup: the amdgpu driver defaults to max_bpc=16 for the HDMI connector. With a HDMI 2.0 monitor (BenQ EL2870U, Max TMDS 340 MHz) at 4K@60Hz, the higher color depth increases bandwidth demand during compbuf reprogramming and makes the timeout happen more often. Adding amdgpu.deep_color=0 helps but does not fix the root cause. Partial workaround: amdgpu.runpm=0 amdgpu.gfx_off=0 amdgpu.deep_color=0 A patch proposed by Giuseppe Ranieri in the CachyOS issue tracker [1] changes the REG_WAIT parameters from 1us*100 to 1000us*30 and resolves the warning for several users with DCN 3.1 hardware. Discussion there is ongoing about whether 2-10us*1000 would be a better fit. [1] https://github.com/CachyOS/linux-cachyos/issues/810 Minxi Hou
