Screen glitches on Qualcomm SM8250 (freedreno) during wake from sleep and brightness change

Device: Retroid Pocket 5 (SM8250, Adreno 650, freedreno)
OS: Rocknix (Linux 7.0.11)
FEX version: from Rocknix Nightly 20260612

Symptoms:
Screen shows heavy glitching (artifacts, flickering, tearing) when:

Waking from sleep

Changing brightness (including brightness fade when idling)

Ocasionally on Steam launching process

Glitches only occur while Steam is running through FEX. All native ARM apps work fine. Without FEX, no glitches.

What I tried:

Panel driver delays (mipi_dsi_msleep(120) after exit_sleep_mode) — no effect

Gamescope flags (--adaptive-sync, --disable-vsync, --immediate-flips) — no effect

Disabling Gamescope entirely (Steam via Sway) — no effect

FEX ThunksDB: setting drm, Vulkan, GL to host passthrough — made it worse (screen blanks on brightness change)

Disabling XRandR, Steam backlight control, Steam fade — no effect

Logs:
Steam systemmanager.txt shows [display] Fade from queried backlight on resume. Kernel DRM debug (drm.debug=0x1ff) shows only DRM_IOCTL_SYNCOBJ_QUERY — no panel errors.

Workaround:
A systemd service does a double blank/unblank cycle on resume. Glitches appear briefly, then screen corrects itself.

Suspected cause:
FEX x86 DRM emulation races with freedreno during blank/unblank/gamma operations on resume.

No source file, test, or entry point is identified. Start by reproducing the wake-from-sleep and brightness glitches on the listed Retroid Pocket 5 setup while Steam runs through FEX, then inspect the FEX DRM emulation interactions with blank, unblank, and gamma operations using the available systemmanager.txt and DRM debug logs. Done means the artifacts no longer occur during resume, brightness changes, or the reported Steam launch case.

Written by the indexing model from the issue text.