[PATCH 03/21] drm/amd/display: Restore Optimized pbn Value if Failed to Disable DSC

[Aurabindo Pillai]

From: Fangzhi Zuo <Jerry.Zuo at amd.com>

Existing last step of dsc policy is to restore pbn value under minimum compression
when try to greedily disable dsc for a stream failed to fit in MST bw.
Optimized dsc params result from optimization step is not necessarily the minimum compression,
therefore it is not correct to restore the pbn under minimum compression rate.

Restore the pbn under minimum compression instead of the value from optimized pbn could result
in the dsc params not correct at the modeset where atomic_check failed due to not
enough bw. One or more monitors connected could not light up in such case.

Restore the optimized pbn value, instead of using the pbn value under minimum
compression.

Cc: Mario Limonciello <mario.limonciello at amd.com>
Cc: Alex Deucher <alexander.deucher at amd.com>
Cc: stable at vger.kernel.org

Reviewed-by: Wayne Lin <wayne.lin at amd.com>
Signed-off-by: Fangzhi Zuo <Jerry.Zuo at amd.com>
Signed-off-by: Aurabindo Pillai <aurabindo.pillai at amd.com>
---
 .../amd/display/amdgpu_dm/amdgpu_dm_mst_types.c | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
index 358c4bff1c40..88b9f4df8fd9 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
@@ -1026,6 +1026,7 @@ static int try_disable_dsc(struct drm_atomic_state *state,
 	int remaining_to_try = 0;
 	int ret;
 	uint16_t fec_overhead_multiplier_x1000 = get_fec_overhead_multiplier(dc_link);
+	int var_pbn;
 
 	for (i = 0; i < count; i++) {
 		if (vars[i + k].dsc_enabled
@@ -1056,13 +1057,18 @@ static int try_disable_dsc(struct drm_atomic_state *state,
 			break;
 
 		DRM_DEBUG_DRIVER("MST_DSC index #%d, try no compression\n", next_index);
+		var_pbn = vars[next_index].pbn;
 		vars[next_index].pbn = kbps_to_peak_pbn(params[next_index].bw_range.stream_kbps, fec_overhead_multiplier_x1000);
 		ret = drm_dp_atomic_find_time_slots(state,
 						    params[next_index].port->mgr,
 						    params[next_index].port,
 						    vars[next_index].pbn);
-		if (ret < 0)
+		if (ret < 0) {
+			DRM_DEBUG_DRIVER("%s:%d MST_DSC index #%d, failed to set pbn to the state, %d\n",
+						__func__, __LINE__, next_index, ret);
+			vars[next_index].pbn = var_pbn;
 			return ret;
+		}
 
 		ret = drm_dp_mst_atomic_check(state);
 		if (ret == 0) {
@@ -1070,14 +1076,17 @@ static int try_disable_dsc(struct drm_atomic_state *state,
 			vars[next_index].dsc_enabled = false;
 			vars[next_index].bpp_x16 = 0;
 		} else {
-			DRM_DEBUG_DRIVER("MST_DSC index #%d, restore minimum compression\n", next_index);
-			vars[next_index].pbn = kbps_to_peak_pbn(params[next_index].bw_range.max_kbps, fec_overhead_multiplier_x1000);
+			DRM_DEBUG_DRIVER("MST_DSC index #%d, restore optimized pbn value\n", next_index);
+			vars[next_index].pbn = var_pbn;
 			ret = drm_dp_atomic_find_time_slots(state,
 							    params[next_index].port->mgr,
 							    params[next_index].port,
 							    vars[next_index].pbn);
-			if (ret < 0)
+			if (ret < 0) {
+				DRM_DEBUG_DRIVER("%s:%d MST_DSC index #%d, failed to set pbn to the state, %d\n",
+							__func__, __LINE__, next_index, ret);
 				return ret;
+			}
 		}
 
 		tried[next_index] = true;
-- 
2.46.0