drm/amd/display: Fix race condition in DPIA AUX transfer

[Why]
This fix was intended for improving on coding style but in the process
uncovers a race condition, which explains why we are getting incorrect
length in DPIA AUX replies. Due to the call path of DPIA AUX going from
DC back to DM layer then again into DC and the added complexities on top
of current DC AUX implementation, a proper fix to rely on current dc_lock
to address the race condition is difficult without a major overhual
on how DPIA AUX is implemented.

[How]
- Add a mutex dpia_aux_lock to protect DPIA AUX transfers
- Remove DMUB_ASYNC_TO_SYNC_ACCESS_* codes and rely solely on
  aux_return_code_type for error reporting and handling
- Separate SET_CONFIG from DPIA AUX transfer because they have quiet
  different processing logic
- Remove unnecessary type casting to and from void * type

Reviewed-by: Nicholas Kazlauskas <Nicholas.Kazlauskas@amd.com>
Acked-by: Jasdeep Dhillon <jdhillon@amd.com>
Signed-off-by: Stylon Wang <stylon.wang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

1 files changed, 14 insertions, 3 deletions

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
index 83436ef3b26b..df3c25e32c65 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
@@ -59,7 +59,9 @@
 #include "signal_types.h"
 #include "amdgpu_dm_crc.h"
 struct aux_payload;
+struct set_config_cmd_payload;
 enum aux_return_code_type;
+enum set_config_status;
 
 /* Forward declarations */
 struct amdgpu_device;
@@ -542,6 +544,13 @@ struct amdgpu_display_manager {
 	 * occurred on certain intel platform
 	 */
 	bool aux_hpd_discon_quirk;
+
+	/**
+	 * @dpia_aux_lock:
+	 *
+	 * Guards access to DPIA AUX
+	 */
+	struct mutex dpia_aux_lock;
 };
 
 enum dsc_clock_force_state {
@@ -785,9 +794,11 @@ void amdgpu_dm_update_connector_after_detect(
 
 extern const struct drm_encoder_helper_funcs amdgpu_dm_encoder_helper_funcs;
 
-int amdgpu_dm_process_dmub_aux_transfer_sync(bool is_cmd_aux,
-					struct dc_context *ctx, unsigned int link_index,
-					void *payload, void *operation_result);
+int amdgpu_dm_process_dmub_aux_transfer_sync(struct dc_context *ctx, unsigned int link_index,
+					struct aux_payload *payload, enum aux_return_code_type *operation_result);
+
+int amdgpu_dm_process_dmub_set_config_sync(struct dc_context *ctx, unsigned int link_index,
+					struct set_config_cmd_payload *payload, enum set_config_status *operation_result);
 
 bool check_seamless_boot_capability(struct amdgpu_device *adev);