drm/amdgpu: Move the mutex_lock to protect the return status of securedisplay command buffer

[Why]
Before we call psp_securedisplay_invoke(), we call
psp_prep_securedisplay_cmd_buf() to prepare and initialize the command
buffer.

However, we didn't use the mutex_lock to protect the status of command
buffer. So when multiple threads are using the command buffer, after
thread A return from psp_securedisplay_invoke() and the command buffer
status is set to SUCCESS, another thread B may call
psp_prep_securedisplay_cmd_buf() and initialize the status to FAILURE
again, and cause Thread A to get a failure return status.

[How]
Move the mutex_lock out of psp_securedisplay_invoke() to its caller to
cover psp_prep_securedisplay_cmd_buf() and the code checking the return
status of command buffer.

Signed-off-by: Alan Liu <[e-mail]>
Reviewed-by: Alex Deucher <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/amdgpu/amdgpu_psp.c

···
 	} else
 		return ret;
 
+	mutex_lock(&psp->securedisplay_context.mutex);
+
 	psp_prep_securedisplay_cmd_buf(psp, &securedisplay_cmd,
 			TA_SECUREDISPLAY_COMMAND__QUERY_TA);
 
 	ret = psp_securedisplay_invoke(psp, TA_SECUREDISPLAY_COMMAND__QUERY_TA);
+
+	mutex_unlock(&psp->securedisplay_context.mutex);
+
 	if (ret) {
 		psp_securedisplay_terminate(psp);
 		/* free securedisplay shared memory */
···
 	    ta_cmd_id != TA_SECUREDISPLAY_COMMAND__SEND_ROI_CRC)
 		return -EINVAL;
 
-	mutex_lock(&psp->securedisplay_context.mutex);
-
 	ret = psp_ta_invoke(psp, ta_cmd_id, &psp->securedisplay_context.context);
-
-	mutex_unlock(&psp->securedisplay_context.mutex);
 
 	return ret;
 }

drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c

···
 
 	switch (op) {
 	case 1:
+		mutex_lock(&psp->securedisplay_context.mutex);
 		psp_prep_securedisplay_cmd_buf(psp, &securedisplay_cmd,
 			TA_SECUREDISPLAY_COMMAND__QUERY_TA);
 		ret = psp_securedisplay_invoke(psp, TA_SECUREDISPLAY_COMMAND__QUERY_TA);
···
 			else
 				psp_securedisplay_parse_resp_status(psp, securedisplay_cmd->status);
 		}
+		mutex_unlock(&psp->securedisplay_context.mutex);
 		break;
 	case 2:
+		mutex_lock(&psp->securedisplay_context.mutex);
 		psp_prep_securedisplay_cmd_buf(psp, &securedisplay_cmd,
 			TA_SECUREDISPLAY_COMMAND__SEND_ROI_CRC);
 		securedisplay_cmd->securedisplay_in_message.send_roi_crc.phy_id = phy_id;
···
 				psp_securedisplay_parse_resp_status(psp, securedisplay_cmd->status);
 			}
 		}
+		mutex_unlock(&psp->securedisplay_context.mutex);
 		break;
 	default:
 		dev_err(adev->dev, "Invalid input: %s\n", str);

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_crc.c

···
 	phy_id = crc_rd_wrk->phy_inst;
 	spin_unlock_irq(&crc_rd_wrk->crc_rd_work_lock);
 
+	mutex_lock(&psp->securedisplay_context.mutex);
+
 	psp_prep_securedisplay_cmd_buf(psp, &securedisplay_cmd,
 						TA_SECUREDISPLAY_COMMAND__SEND_ROI_CRC);
 	securedisplay_cmd->securedisplay_in_message.send_roi_crc.phy_id =
···
 			psp_securedisplay_parse_resp_status(psp, securedisplay_cmd->status);
 		}
 	}
+
+	mutex_unlock(&psp->securedisplay_context.mutex);
 }
 
 static void