AMD General + Harry, Leo
> -----Original Message----- > From: Thorsten Leemhuis <[email protected]> > Sent: Wednesday, May 20, 2026 4:59 AM > To: Minxi Hou <[email protected]>; [email protected] > Cc: [email protected]; Eric Naim <[email protected]>; Pinninti, > Bhuvana Chandra <[email protected]>; Linux kernel > regressions list <[email protected]>; Deucher, Alexander > <[email protected]>; Antonio Quartulli > <[email protected]>; Koenig, Christian <[email protected]> > Subject: Re: 7.0-rc4 dcn31_program_compbuf_size trace > > [+a few people] > > On 5/18/26 10:08, Minxi Hou wrote: > > 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" > > Antonio posted a RFC fix for that comment here with a reference to a warning > that on a *very quick* look looks similar: > https://lore.kernel.org/all/20260519144509.2646680-1- > [email protected]/ > > Wondering if we need a ticket here to get this resolved: > https://gitlab.freedesktop.org/drm/amd/-/work_items/ > > But from the reply to Antonio's patch is sounds like it's not needed. > > Ciao, Thorsten > > > 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
