drm/amd/display: temp w/a for dGPU to enter idle optimizations

[Why&How]
vblank immediate disable currently does not work for all asics. On
DCN401, the vblank interrupts never stop coming, and hence we never
get a chance to trigger idle optimizations.

Add a workaround to enable immediate disable only on APUs for now. This
adds a 2-frame delay for triggering idle optimization, which is a
negligible overhead.

Fixes: 58a261bfc9 ("drm/amd/display: use a more lax vblank enable policy for older ASICs")
Fixes: e45b6716de ("drm/amd/display: use a more lax vblank enable policy for DCN35+")
Cc: Mario Limonciello <[email protected]>
Cc: Alex Deucher <[email protected]>
Reviewed-by: Harry Wentland <[email protected]>
Reviewed-by: Rodrigo Siqueira <[email protected]>
Signed-off-by: Aurabindo Pillai <[email protected]>
Signed-off-by: Wayne Lin <[email protected]>
Tested-by: Daniel Wheeler <[email protected]>
Signed-off-by: Alex Deucher <[email protected]>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

@@ -8389,7 +8389,8 @@ static void manage_dm_interrupts(struct amdgpu_device *adev,
 		if (amdgpu_ip_version(adev, DCE_HWIP, 0) <
 		    IP_VERSION(3, 5, 0) ||
 		    acrtc_state->stream->link->psr_settings.psr_version <
-		    DC_PSR_VERSION_UNSUPPORTED) {
+		    DC_PSR_VERSION_UNSUPPORTED ||
+		    !(adev->flags & AMD_IS_APU)) {
 			timing = &acrtc_state->stream->timing;
 
 			/* at least 2 frames */