As attempt to find the cause I've tried different kernels.
The first step was to try kernel before: update drm to linux 6.6.12 [1], which I suceffuly build and tries on current snapshot system. The issue was reproduced. Unfortently I can't simple switch to something before because system doesn't boot with miltiple crasshes regarding invlaid syscall. I assume that the cause is PT_OPENBSD_SYSCALLS [2]. I've tried to backport that to early kernel to use as part of bisect to find who brokes it, but it quite fragile :( So, here I get all commits which changes sys/dev/pci/drm/i915 between unlock the base to move to 7.4-current [3] and update drm. It wasn't so many, just 22. I've reverted all of them in reverse order and tries each separatley [4]. Well, isssue is reproducing with both firmares: from current snapshot and 7.4. So, I have no idea how to debug it future. Can anyone suggest anyway? Footnotes: [1] https://github.com/openbsd/src/commit/f005ef32267c16bdb134f0e9fa4477dbe07c263a [2] https://github.com/openbsd/src/commit/4a066defabc39dafcb616ade6ee82c10212ac361 [3] https://github.com/openbsd/src/commit/67babe865022f800d11adfe4f8b70c437e1e3e30 [4] https://github.com/catap/OpenBSD-src/tree/LG5k-issue -- wbr, Kirill