[PATCH 4.20 160/183] drm/amd/display: Fix MST reboot/poweroff sequence

[Greg Kroah-Hartman]

4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Leo (Hanghong) Ma <hanghong.ma@xxxxxxx>

commit d2f0b53bda3193874f3905bc839888f895d1c0cf upstream.

[Why]

drm_dp_mst_topology_mgr_suspend() is added into the new reboot
sequence, which disables the UP request at the beginning.
Therefore sideband messages are blocked.

[How]

Finish MST sideband message transaction before UP request is
suppressed.

Signed-off-by: Leo (Hanghong) Ma <hanghong.ma@xxxxxxx>
Reviewed-by: Roman Li <Roman.Li@xxxxxxx>
Acked-by: Leo Li <sunpeng.li@xxxxxxx>
Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -704,12 +704,13 @@ static int dm_suspend(void *handle)
 	struct amdgpu_display_manager *dm = &adev->dm;
 	int ret = 0;
 
+	WARN_ON(adev->dm.cached_state);
+	adev->dm.cached_state = drm_atomic_helper_suspend(adev->ddev);
+
 	s3_handle_mst(adev->ddev, true);
 
 	amdgpu_dm_irq_suspend(adev);
 
-	WARN_ON(adev->dm.cached_state);
-	adev->dm.cached_state = drm_atomic_helper_suspend(adev->ddev);
 
 	dc_set_power_state(dm->dc, DC_ACPI_CM_POWER_STATE_D3);