[PATCH] drm/amd/display: pbn_div need be updated for hotplug event

[Alex Deucher <alexander.deucher@amd.com>]

From: Wayne Lin <wayne.lin@amd.com>

link_rate sometime will be changed when DP MST connector hotplug, so
pbn_div also need be updated; otherwise, it will mismatch with
link_rate, causes no output in external monitor.

This is a backport of
commit 9cdef4f72037 ("drm/amd/display: pbn_div need be updated for hotplug event")
to 6.1.  This fixes a display light up failure on some docking stations.

Cc: stable@vger.kernel.org
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Reviewed-by: Jerry Zuo <jerry.zuo@amd.com>
Acked-by: Rodrigo Siqueira <rodrigo.siqueira@amd.com>
Signed-off-by: Wade Wang <wade.wang@hp.com>
Signed-off-by: Wayne Lin <wayne.lin@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 9cdef4f720376ef0fb0febce1ed2377c19e531f9)
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

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 13e0b521e3db..f02e509d5fac 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -6677,8 +6677,7 @@ static int dm_encoder_helper_atomic_check(struct drm_encoder *encoder,
 	if (IS_ERR(mst_state))
 		return PTR_ERR(mst_state);
 
-	if (!mst_state->pbn_div)
-		mst_state->pbn_div = dm_mst_get_pbn_divider(aconnector->mst_port->dc_link);
+	mst_state->pbn_div = dm_mst_get_pbn_divider(aconnector->mst_port->dc_link);
 
 	if (!state->duplicated) {
 		int max_bpc = conn_state->max_requested_bpc;
-- 
2.42.0