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[8/9,SRU,Jammy] drm/amd/display: Don't lock connection_mutex for DMUB HPD

Message ID 20211215065730.390346-9-vicamo.yang@canonical.com
State New
Headers show
Series Support USB4 DP alt mode for AMD Yellow Carp graphics card | expand

Commit Message

You-Sheng Yang Dec. 15, 2021, 6:57 a.m. UTC 
From: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>

BugLink: https://bugs.launchpad.net/bugs/1953008

[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>
(cherry picked from commit d82b3266ef88dc10fe0e7031b2bd8ba7eedb7e59)
Signed-off-by: You-Sheng Yang <vicamo.yang@canonical.com>
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 4 ----
 1 file changed, 4 deletions(-)
diff mbox series

Patch

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 74d60e937af0..d5a579d9fa9e 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);