[PATCH 3/3] drm/amd/display: report synced Apple 5K tiles to PowerPlay for MCLK switch

[Richard Lane <richardlanedev@gmail.com>]

When driving both 2560x2880 tiles of an Apple 5K iMac panel, Display
Core's program_timing_sync() already aligns both CRTCs in hardware
during dc_commit_streams() because the two streams share identical
timings.

However, on DCE < 12 (iMac15,1 through Polaris-based iMac19,1), Display
Core leaves pp_display_cfg.all_displays_in_sync unset. Because PowerPlay
is not informed that the two streams have synchronized vertical blanking
intervals, SMU7 prevents MCLK switching at idle or causes modeset
underflows.

Report all_displays_in_sync = true to PowerPlay after committing both
tiled streams so SMU7 knows the tiles blank simultaneously and can
safely downclock MCLK at idle.

Signed-off-by: Richard Lane <richardlanedev@gmail.com>
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index 548f975c7324..384a81371f80 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -4788,6 +4788,19 @@ static void amdgpu_dm_commit_streams(struct drm_atomic_commit *state,
 	mutex_lock(&dm->dc_lock);
 	dc_exit_ips_for_hw_access(dm->dc);
 	WARN_ON(!dc_commit_streams(dm->dc, &params));
+	/*
+	 * DCE < 12 leaves all_displays_in_sync unset; report synchronized
+	 * Apple 5K tiles to PowerPlay after commit so SMU7 can downclock MCLK
+	 * at idle without modeset underflows.
+	 */
+	if (params.stream_count == 2 &&
+	    params.streams[0]->link->tiled_peer == params.streams[1]->link) {
+		struct dm_pp_display_configuration *pp_cfg =
+			&dm->dc->current_state->pp_display_cfg;
+
+		pp_cfg->all_displays_in_sync = true;
+		dm_pp_apply_display_requirements(dm->dc->ctx, pp_cfg);
+	}
 
 	bool frl_stream_found = false;
 
-- 
2.55.0