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Subject[PATCH 5.14 056/125] drm/amd/display: Fix deadlock when falling back to v2 from v3
Date
From: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>

commit ad76744b041d8c87ef1c9adbb04fb7eaa20a179e upstream.

[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
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
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 @@ static enum mod_hdcp_status mod_hdcp_rem
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 = mod_hdcp_remove_display_from_topology_v2(hdcp, index);
@@ -115,8 +116,6 @@ static enum mod_hdcp_status mod_hdcp_rem
HDCP_TOP_REMOVE_DISPLAY_TRACE(hdcp, display->index);
}

- mutex_unlock(&psp->dtm_context.mutex);
-
return status;
}

@@ -218,6 +217,7 @@ static enum mod_hdcp_status mod_hdcp_add
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 = mod_hdcp_add_display_to_topology_v2(hdcp, display);
@@ -227,8 +227,6 @@ static enum mod_hdcp_status mod_hdcp_add
HDCP_TOP_ADD_DISPLAY_TRACE(hdcp, display->index);
}

- mutex_unlock(&psp->dtm_context.mutex);
-
return status;
}


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