After commit a637a140ab860310 ("drm/amd/display: Allocate DCN32/1 dmub
memory to GTT"), a machine with a Radeon RX 7900 shows random garbage on
the screen. It reproduces sporadically, but at times it is so bad the
machine is more or less unusable.The garbage is always horizontal bars extending across the entire screen, always approximately 200 pixels tall on a 3840x2160 screen, for what looks like a single frame. The bars are mostly black, but will sometimes exhibit striping and periodic artifacts which smell like non-framebuffer data is being rendered to the screen. It took some patience on the "good" side, but I was able to nail it down to commit a637a140ab860310818a14fb4d37e39e51a06be4 with this bisect: bad: [cee9395acd8043be0644b25c34bfa86623f2b935] Linux 7.3-rc1 good: [8d3ae59288f1e7d58d76558a6ee96d533bc5019f] Linux 7.2 good: [55ab7e14222e5f0b0fd9f7711ca391d2924b35e3] Merge tag 'for-7.3/block-20260819' of git://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux bad: [df51bdc5e80dae43cab81f6cc641e98638303c88] Merge tag 'mtd/for-7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/mtd/linux bad: [29daacacf4cd84e6917f09de6a99fb170071c14c] Merge tag 'drm-rust-next-2026-08-08' of https://gitlab.freedesktop.org/drm/rust/kernel into drm-next good: [fff648aec5e2790d117a0ec5c849a284d9d33d70] drm/amdgpu: include amdgpu_video_codecs.h only where needed bad: [336e0cd576817ac64a4b394ca2b3680029f3e37f] Revert "drm/amdgpu: fix aperture mapping leak" bad: [789f7486a384ca58b9d7a76abba5efa0e80e8dab] drm/amd/display: Test plane colorop helper walkers good: [e0e426f10ad653c5e9dd33fb4a76d55f06101992] drm/amd/display: Test helper_check_state rejects bad: [982b2a43682b55e7d9800000f2592832ff2865ba] drm/amdgpu: Fix IP block NULL check during soft reset bad: [9102b39fa924dcc3dc75a3137bfa9633c40b88c0] drm/amdgpu/userq: fix indefinite fence wait during GPU reset bad: [b23470a026afe64de5c1df4ad181587b49c22923] drm/amd/display: Exit LS for ISHARP before coefficient write bad: [f02b2e47355e9d381a7f34acc997e1c47879ca21] drm/amd/display: Add KUnit test for wb jobs bad: [c6a13d145cc811b19c8a0620f25868cf7d5700c0] drm/amd/display: remove unused dcn42 socbb values good: [1d8327353de6f1f34063840f362c208c84064f54] drm/amd/display: Fix VABC Init and OLED Support bad: [a637a140ab860310818a14fb4d37e39e51a06be4] drm/amd/display: Allocate DCN32/1 dmub memory to GTT first 'bad' commit: [a637a140ab860310818a14fb4d37e39e51a06be4] drm/amd/display: Allocate DCN32/1 dmub memory to GTT Sure enough, reverting a637a140ab860310818a14fb4d37e39e51a06be4 on top of v7.3 completely and totally eliminates the problem for me. Mikhail has separately reported this regression: https://lore.kernel.org/all/[email protected]/ ...but it seems to be much more consistent for me than for Mikhail, it's never taken more than 30 minutes even when the machine is completely idle. I've also never been able to reproduce any artifact one single time without commit a637a140, despite a lot of effort. I'm not sure reverting this is the right way forward, since presumably this would re-regress the timing issue Fangzhi alluded to in the original commit. But nobody has proposed anything concrete yet... so let's start the discussion here. I'm happy to help test other better ideas as well :) Signed-off-by: Calvin Owens <[email protected]> --- .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_dmub.c | 11 ++--------- 1 file changed, 2 insertions(+), 9 deletions(-) diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_dmub.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_dmub.c index 9ff25bc8ee5ae..870534b7cf46d 100644 --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_dmub.c +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_dmub.c @@ -511,7 +511,6 @@ int dm_dmub_sw_init(struct amdgpu_device *adev) DMUB_WINDOW_MEMORY_TYPE_FB, /* DMUB_WINDOW_CURSOR_OFFLOAD */ }; int r; - int mem_domain = AMDGPU_GEM_DOMAIN_GTT; switch (amdgpu_ip_version(adev, DCE_HWIP, 0)) { case IP_VERSION(2, 1, 0): @@ -648,19 +647,13 @@ int dm_dmub_sw_init(struct amdgpu_device *adev) return -EINVAL; } - /* Limit to allocate dmub to GTT on DCN32/1 - * TODO: Other asics with GDDR7 may have worse latency - */ - if (dmub_asic != DMUB_ASIC_DCN32 && - dmub_asic != DMUB_ASIC_DCN321) - mem_domain |= AMDGPU_GEM_DOMAIN_VRAM; - /* * Allocate a framebuffer based on the total size of all the regions. * TODO: Move this into GART. */ r = amdgpu_bo_create_kernel(adev, region_info.fb_size, PAGE_SIZE, - mem_domain, + AMDGPU_GEM_DOMAIN_VRAM | + AMDGPU_GEM_DOMAIN_GTT, &adev->dm.dmub_bo, &adev->dm.dmub_bo_gpu_addr, &adev->dm.dmub_bo_cpu_addr); -- 2.47.3
