can: m_can: Read register PSR only on error

Only read register PSR if there is an error indicated in irqstatus.
Signed-off-by: Markus Schneider-Pargmann <msp@baylibre.com>
Link: https://lore.kernel.org/all/20221206115728.1056014-4-msp@baylibre.comSigned-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/m_can/m_can.c

@@ -910,7 +910,6 @@ static int m_can_rx_handler(struct net_device *dev, int quota, u32 irqstatus)
 	struct m_can_classdev *cdev = netdev_priv(dev);
 	int rx_work_or_err;
 	int work_done = 0;
-	u32 psr;
 
 	if (!irqstatus)
 		goto end;
@@ -936,13 +935,13 @@ static int m_can_rx_handler(struct net_device *dev, int quota, u32 irqstatus)
 		}
 	}
 
-	psr = m_can_read(cdev, M_CAN_PSR);
-
 	if (irqstatus & IR_ERR_STATE)
-		work_done += m_can_handle_state_errors(dev, psr);
+		work_done += m_can_handle_state_errors(dev,
+						       m_can_read(cdev, M_CAN_PSR));
 
 	if (irqstatus & IR_ERR_BUS_30X)
-		work_done += m_can_handle_bus_errors(dev, irqstatus, psr);
+		work_done += m_can_handle_bus_errors(dev, irqstatus,
+						     m_can_read(cdev, M_CAN_PSR));
 
 	if (irqstatus & IR_RF0N) {
 		rx_work_or_err = m_can_do_rx_poll(dev, (quota - work_done));