On GPU reset, dm_suspend() takes dc_lock and leaves it for dm_resume()
to drop. If amdgpu_dm_commit_zero_streams() or dm_dmub_hw_init() fails,
the function returns with the lock still held. The matching resume path
is then skipped, so every later dc_lock take hangs.

Release the cached DC state and unlock before returning the error.

Fixes: 3cf7a0bc87f0 ("drm/amd/display: Catch failures for amdgpu_dm_commit_zero_streams()")
Fixes: 2b6943df5413 ("drm/amd/display: Pass up errors for reset GPU that fails to init HW")
Cc: stable@vger.kernel.org
Signed-off-by: Linkai Gong <gonglinkai@kylinos.cn>
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 6 ++++++
 1 file changed, 6 insertions(+)
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 941c1a312824..214aca906fe1 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -3511,6 +3511,9 @@ static int dm_suspend(struct amdgpu_ip_block *ip_block)
 		res = amdgpu_dm_commit_zero_streams(dm->dc);
 		if (res != DC_OK) {
 			drm_err(adev_to_drm(adev), "Failed to commit zero streams: %d\n", res);
+			dc_state_release(dm->cached_dc_state);
+			dm->cached_dc_state = NULL;
+			mutex_unlock(&dm->dc_lock);
 			return -EINVAL;
 		}
 
@@ -3824,6 +3827,9 @@ static int dm_resume(struct amdgpu_ip_block *ip_block)
 		r = dm_dmub_hw_init(adev);
 		if (r) {
 			drm_err(adev_to_drm(adev), "DMUB interface failed to initialize: status=%d\n", r);
+			dc_state_release(dm->cached_dc_state);
+			dm->cached_dc_state = NULL;
+			mutex_unlock(&dm->dc_lock);
 			return r;
 		}
 
-- 
2.25.1

On 8/19/26 00:47, Linkai Gong wrote:
> On GPU reset, dm_suspend() takes dc_lock and leaves it for dm_resume()
> to drop. If amdgpu_dm_commit_zero_streams() or dm_dmub_hw_init() fails,
> the function returns with the lock still held. The matching resume path
> is then skipped, so every later dc_lock take hangs.
> 
> Release the cached DC state and unlock before returning the error.
> 
> Fixes: 3cf7a0bc87f0 ("drm/amd/display: Catch failures for amdgpu_dm_commit_zero_streams()")
> Fixes: 2b6943df5413 ("drm/amd/display: Pass up errors for reset GPU that fails to init HW")
> Cc: stable@vger.kernel.org
> Signed-off-by: Linkai Gong <gonglinkai@kylinos.cn>

Great finding and fix.  I'll get this added to amd-staging-drm-next.

Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>

> ---
>   drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 6 ++++++
>   1 file changed, 6 insertions(+)
> 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 941c1a312824..214aca906fe1 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -3511,6 +3511,9 @@ static int dm_suspend(struct amdgpu_ip_block *ip_block)
>   		res = amdgpu_dm_commit_zero_streams(dm->dc);
>   		if (res != DC_OK) {
>   			drm_err(adev_to_drm(adev), "Failed to commit zero streams: %d\n", res);
> +			dc_state_release(dm->cached_dc_state);
> +			dm->cached_dc_state = NULL;
> +			mutex_unlock(&dm->dc_lock);
>   			return -EINVAL;
>   		}
>   
> @@ -3824,6 +3827,9 @@ static int dm_resume(struct amdgpu_ip_block *ip_block)
>   		r = dm_dmub_hw_init(adev);
>   		if (r) {
>   			drm_err(adev_to_drm(adev), "DMUB interface failed to initialize: status=%d\n", r);
> +			dc_state_release(dm->cached_dc_state);
> +			dm->cached_dc_state = NULL;
> +			mutex_unlock(&dm->dc_lock);
>   			return r;
>   		}
>