From 91840c6ef7d60a34d054def64d3b74793b18156e Mon Sep 17 00:00:00 2001
From: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Date: Fri, 22 Oct 2021 16:14:24 -0400
Subject: drm/amd/display: Fix deadlock when falling back to v2 from v3
Git-commit: ad76744b041d8c87ef1c9adbb04fb7eaa20a179e
Patch-mainline: v5.15
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
Alt-commit: f638d7505f99bca9436aac37b2a1ecb3f84803a5

[Why]
A deadlock in the kernel occurs when we fallback from the V3 to V2
add_topology_to_display or remove_topology_to_display because they
both try to acquire the dtm_mutex but recursive locking isn't
supported on mutex_lock().

[How]
Make the mutex_lock/unlock more fine grained and move them up such that
they're only required for the psp invocation itself.

Fixes: bf62221e9d0e ("drm/amd/display: Add DCN3.1 HDCP support")

Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Reviewed-by: Aric Cyr <aric.cyr@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
 drivers/gpu/drm/amd/display/modules/hdcp/hdcp_psp.c |    6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

--- a/drivers/gpu/drm/amd/display/modules/hdcp/hdcp_psp.c
+++ b/drivers/gpu/drm/amd/display/modules/hdcp/hdcp_psp.c
@@ -105,6 +105,7 @@
 	dtm_cmd->dtm_status = TA_DTM_STATUS__GENERIC_FAILURE;
 
 	psp_dtm_invoke(psp, dtm_cmd->cmd_id);
+	mutex_unlock(&psp->dtm_context.mutex);
 
 	if (dtm_cmd->dtm_status != TA_DTM_STATUS__SUCCESS) {
 		status = remove_display_from_topology_v2(hdcp, index);
@@ -115,8 +116,6 @@
 		HDCP_TOP_REMOVE_DISPLAY_TRACE(hdcp, display->index);
 	}
 
-	mutex_unlock(&psp->dtm_context.mutex);
-
 	return status;
 }
 
@@ -205,6 +204,7 @@
 	dtm_cmd->dtm_in_message.topology_update_v3.link_hdcp_cap = link->hdcp_supported_informational;
 
 	psp_dtm_invoke(psp, dtm_cmd->cmd_id);
+	mutex_unlock(&psp->dtm_context.mutex);
 
 	if (dtm_cmd->dtm_status != TA_DTM_STATUS__SUCCESS) {
 		status = add_display_to_topology_v2(hdcp, display);
@@ -214,8 +214,6 @@
 		HDCP_TOP_ADD_DISPLAY_TRACE(hdcp, display->index);
 	}
 
-	mutex_unlock(&psp->dtm_context.mutex);
-
 	return status;
 }