From b189dae4193a0d646c35e50bbda175d4dd0d8e31 Mon Sep 17 00:00:00 2001
From: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Date: Thu, 4 Nov 2021 16:52:06 -0400
Subject: drm/amd/display: Don't lock connection_mutex for DMUB HPD
Git-commit: d82b3266ef88dc10fe0e7031b2bd8ba7eedb7e59
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]
Per DRM spec we only need to hold that lock when touching
connector->state - which we do not do in that handler.
Taking this locking introduces unnecessary dependencies with other
threads which is bad for performance and opens up the potential for
a deadlock since there are multiple locks being held at once.
[How]
Remove the connection_mutex lock/unlock routine and just iterate over
the drm connectors normally. The iter helpers implicitly lock the
connection list so this is safe to do.
DC link access also does not need to be guarded since the link
table is static at creation - we don't dynamically add or remove links,
just streams.
Fixes: e27c41d5b068 ("drm/amd/display: Support for DMUB HPD interrupt handling")
Reviewed-by: Jude Shih <shenshih@amd.com>
Acked-by: Anson Jacob <Anson.Jacob@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 4 ----
1 file changed, 4 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 d0d38d3631dc..6aafcc14b479 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -669,10 +669,7 @@ void dmub_hpd_callback(struct amdgpu_device *adev, struct dmub_notification *not
return;
}
- drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
-
link_index = notify->link_index;
-
link = adev->dm.dc->links[link_index];
drm_connector_list_iter_begin(dev, &iter);
@@ -685,7 +682,6 @@ void dmub_hpd_callback(struct amdgpu_device *adev, struct dmub_notification *not
}
}
drm_connector_list_iter_end(&iter);
- drm_modeset_unlock(&dev->mode_config.connection_mutex);
if (hpd_aconnector)
handle_hpd_irq_helper(hpd_aconnector);
--
2.38.1