Both EDID moments the system has are now captured and carried to the
compositor's frame clock:
- EFI: the loader derives refresh from the preferred detailed timing
(pixel clock / total pixels) while GOP is still alive — the only moment
it is readable — and hands it through the boot handoff into the
display0 node's DisplayInfo (new refresh_hz field, 0 = unknown).
- GPU: the virtio-gpu driver derives the same figure from its own EDID
read and carries it in the attach_scanout announce (request.y).
updateFrameClock() re-derives the interval from the active backend's
info at bring-up and again on every backend change — the boot
framebuffer's clock dies with the GOP floor at upgrade, replaced by the
GPU's rate. Unknown rate defaults to 60 Hz; the result is clamped to
[30, 120] Hz so a mis-parsed EDID can neither starve nor flood the
compositor. Rate only, never phase: without vblank, presents still
free-run (docs/display-v2.md, 'Fenced is not vsync').
Observed in QEMU: OVMF exposes no EDID for the VGA adapter, so the GOP
floor logs 'frame clock 62 Hz (default)' (real firmware does expose it);
the virtio-gpu EDID advertises 75 Hz and the upgrade logs 'frame clock
76 Hz (panel EDID)'. The display kernel test asserts refresh_hz rides
the seeded node; all 7 display QEMU cases pass.
Daniel Samson
ec6e888076