drm/amd/display: Test VRR pageflip completion

[WHAT]
dm_pflip_high_irq() only ever ran with VRR inactive, so the
scanout position query and the front-porch path that queues the
pageflip event on the vblank event list were never reached.

[HOW]
Add a fake timing generator reporting a scanout position past the
start of the front porch, plus a fixture that puts a submitted flip on
an active-VRR stream.

Assisted-by: Copilot:Claude-Opus-5
Reviewed-by: Bhawanpreet Lakha <bhawanpreet.lakha@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: George Zhang <george.zhang@amd.com>
Tested-by: Dan Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

0 files changed, 0 insertions, 0 deletions