From 16c5dcc95417fe343a2547f80924721d41f4d552 Mon Sep 17 00:00:00 2001
From: Jimmy Kizito <Jimmy.Kizito@amd.com>
Date: Fri, 1 Oct 2021 22:36:19 +0800
Subject: drm/amd/display: Fix concurrent dynamic encoder assignment.
Git-commit: 8da5cbafb2ea1c33964ed6e5c79e9f2ebe001b57
Patch-mainline: v5.16-rc1
References: jsc#PED-1166 jsc#PED-1168 jsc#PED-1170 jsc#PED-1218 jsc#PED-1220 jsc#PED-1222 jsc#PED-1223 jsc#PED-1225

[Why]
Trying to enable multiple displays simultaneously exposed shortcomings
with the algorithm for dynamic link encoder assignment.

The main problems were:
- Assuming stream order remained constant across states would
sometimes lead to invalid DIG encoder assignment.
- Incorrect logic for deciding whether or not a DIG could support a
stream would also sometimes lead to invalid DIG encoder assignment.
- Changes in encoder assignment were wholesale while updating of the
pipe backend is incremental. This would lead to the hardware state
not matching the software state even with valid encoder assignments.

[How]

The following changes fix the identified problems.
- Use stream pointer rather than stream index to track streams across
states.
- Fix DIG compatibility check by examining the link signal type
rather than the stream signal type.
- Modify assignment algorithm to make incremental updates so software
and hardware states remain coherent.

Additionally:
- Add assertions and an encoder assignment validation
function link_enc_cfg_validate() to detect potential problems with
encoder assignment closer to their root cause.
- Reduce the frequency with which the assignment algorithm is
executed. It should not be necessary for fast state validation.

Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Solomon Chiu <solomon.chiu@amd.com>
Signed-off-by: Jimmy Kizito <Jimmy.Kizito@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
 drivers/gpu/drm/amd/display/dc/core/dc_link.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link.c b/drivers/gpu/drm/amd/display/dc/core/dc_link.c
index 74da226efffe..81bf1e5a64c8 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc_link.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_link.c
@@ -1926,9 +1926,9 @@ void blank_all_dp_displays(struct dc *dc, bool hw_init)
 			}
 
 			if ((signal != SIGNAL_TYPE_EDP && status == DC_OK && dpcd_power_state == DP_POWER_STATE_D0) ||
-				(!hw_init && dc->links[i]->link_enc->funcs->is_dig_enabled(dc->links[i]->link_enc))) {
-				if (dc->links[i]->ep_type == DISPLAY_ENDPOINT_PHY &&
-						dc->links[i]->link_enc->funcs->get_dig_frontend) {
+					(!hw_init && dc->links[i]->link_enc &&
+					dc->links[i]->link_enc->funcs->is_dig_enabled(dc->links[i]->link_enc))) {
+				if (dc->links[i]->link_enc->funcs->get_dig_frontend) {
 					fe = dc->links[i]->link_enc->funcs->get_dig_frontend(dc->links[i]->link_enc);
 					if (fe == ENGINE_ID_UNKNOWN)
 						continue;
-- 
2.38.1