drm/amd/display: Handle I2C-over-AUX write channel status update

[Why]
When writing long AUX commands some sinks will respond will write status
update requiring source to read status.

[How]
When a write request is replied with data (AUX_ACK_M), retry a read of
write status to determine when the write is completed.

Reviewed-by: Martin Leung <[e-mail]>
Tested-by: Daniel Wheeler <[e-mail]>
Acked-by: Agustin Gutierrez <[e-mail]>
Signed-off-by: Aric Cyr <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

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

···
 	payload.i2c_over_aux = (msg->request & DP_AUX_NATIVE_WRITE) == 0;
 	payload.write = (msg->request & DP_AUX_I2C_READ) == 0;
 	payload.mot = (msg->request & DP_AUX_I2C_MOT) != 0;
+	payload.write_status_update =
+			(msg->request & DP_AUX_I2C_WRITE_STATUS_UPDATE) != 0;
 	payload.defer_delay = 0;
 
 	result = dc_link_aux_transfer_raw(TO_DM_AUX(aux)->ddc_service, &payload,

drivers/gpu/drm/amd/display/dc/core/dc_link_ddc.c

···
 		payload.address = address;
 		payload.reply = NULL;
 		payload.defer_delay = get_defer_delay(ddc);
+		payload.write_status_update = false;
 
 		if (write_size != 0) {
 			payload.write = true;
···
 	do {
 		struct aux_payload current_payload;
 		bool is_end_of_payload = (retrieved + DEFAULT_AUX_MAX_DATA_SIZE) >=
-			payload->length;
+				payload->length ? true : false;
+		uint32_t payload_length = is_end_of_payload ?
+				payload->length - retrieved : DEFAULT_AUX_MAX_DATA_SIZE;
 
 		current_payload.address = payload->address;
 		current_payload.data = &payload->data[retrieved];
 		current_payload.defer_delay = payload->defer_delay;
 		current_payload.i2c_over_aux = payload->i2c_over_aux;
-		current_payload.length = is_end_of_payload ?
-			payload->length - retrieved : DEFAULT_AUX_MAX_DATA_SIZE;
-		/* set mot (middle of transaction) to false
-		 * if it is the last payload
-		 */
+		current_payload.length = payload_length;
+		/* set mot (middle of transaction) to false if it is the last payload */
 		current_payload.mot = is_end_of_payload ? payload->mot:true;
+		current_payload.write_status_update = false;
 		current_payload.reply = payload->reply;
 		current_payload.write = payload->write;
 
 		ret = dc_link_aux_transfer_with_retries(ddc, &current_payload);
 
-		retrieved += current_payload.length;
+		retrieved += payload_length;
 	} while (retrieved < payload->length && ret == true);
 
 	return ret;

drivers/gpu/drm/amd/display/dc/dce/dce_aux.c

···
 static enum i2caux_transaction_action i2caux_action_from_payload(struct aux_payload *payload)
 {
 	if (payload->i2c_over_aux) {
+		if (payload->write_status_update) {
+			if (payload->mot)
+				return I2CAUX_TRANSACTION_ACTION_I2C_STATUS_REQUEST_MOT;
+			else
+				return I2CAUX_TRANSACTION_ACTION_I2C_STATUS_REQUEST;
+		}
 		if (payload->write) {
 			if (payload->mot)
 				return I2CAUX_TRANSACTION_ACTION_I2C_WRITE_MOT;
-			return I2CAUX_TRANSACTION_ACTION_I2C_WRITE;
+			else
+				return I2CAUX_TRANSACTION_ACTION_I2C_WRITE;
 		}
 		if (payload->mot)
 			return I2CAUX_TRANSACTION_ACTION_I2C_READ_MOT;
+
 		return I2CAUX_TRANSACTION_ACTION_I2C_READ;
 	}
 	if (payload->write)
 		return I2CAUX_TRANSACTION_ACTION_DP_WRITE;
+
 	return I2CAUX_TRANSACTION_ACTION_DP_READ;
 }
 
···
 		aux_defer_retries = 0,
 		aux_i2c_defer_retries = 0,
 		aux_timeout_retries = 0,
-		aux_invalid_reply_retries = 0;
+		aux_invalid_reply_retries = 0,
+		aux_ack_m_retries = 0;
 
 	if (ddc_pin) {
 		aux_engine = ddc->ctx->dc->res_pool->engines[ddc_pin->pin_data->en];
···
 									aux_defer_retries,
 									AUX_MAX_RETRIES);
 						goto fail;
-					} else {
+					} else 
 						udelay(300);
+				} else if (payload->write && ret > 0) {
+					/* sink requested more time to complete the write via AUX_ACKM */
+					if (++aux_ack_m_retries >= AUX_MAX_RETRIES) {
+						DC_TRACE_LEVEL_MESSAGE(DAL_TRACE_LEVEL_ERROR,
+								LOG_FLAG_Error_I2cAux,
+								"dce_aux_transfer_with_retries: FAILURE: aux_ack_m_retries=%d >= AUX_MAX_RETRIES=%d",
+								aux_ack_m_retries,
+								AUX_MAX_RETRIES);
+						goto fail;
 					}
+
+					/* retry reading the write status until complete
+					 * NOTE: payload is modified here
+					 */
+					payload->write = false;
+					payload->write_status_update = true;
+					payload->length = 0;
+					udelay(300);
+
 				} else
 					return true;
 			break;

drivers/gpu/drm/amd/display/include/i2caux_interface.h

···
 	 * reset it to read data */
 	bool write;
 	bool mot;
+	bool write_status_update;
+
 	uint32_t address;
 	uint32_t length;
 	uint8_t *data;
···
 	 * zero means "use default value"
 	 */
 	uint32_t defer_delay;
+
 };
 
 struct aux_command {