From: Marc Kleine-Budde <mkl@pengutronix.de>
Date: Wed, 9 Oct 2019 15:15:37 +0200
Subject: can: flexcan: flexcan_irq_state(): only read timestamp if needed

Git-commit: 58ed8e77d3123acb6ece7d016c8db393d5c0d488
Patch-mainline: v5.5-rc1
References: jsc#SLE-12251

The function flexcan_irq_state() checks the controller for CAN state
changes and pushes a skb with the new state and a timestamp into the
rx-offload framework.

This patch optimizes the function by only reading the timestamp, if a
state change is detected.

Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Mian Yousaf Kaukab <ykaukab@suse.de>
---
 drivers/net/can/flexcan.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/can/flexcan.c b/drivers/net/can/flexcan.c
index 362ed90c701f..148c0a3fab24 100644
--- a/drivers/net/can/flexcan.c
+++ b/drivers/net/can/flexcan.c
@@ -743,8 +743,6 @@ static void flexcan_irq_state(struct net_device *dev, u32 reg_esr)
 	u32 timestamp;
 	int err;
 
-	timestamp = priv->read(&regs->timer) << 16;
-
 	flt = reg_esr & FLEXCAN_ESR_FLT_CONF_MASK;
 	if (likely(flt == FLEXCAN_ESR_FLT_CONF_ACTIVE)) {
 		tx_state = unlikely(reg_esr & FLEXCAN_ESR_TX_WRN) ?
@@ -764,6 +762,8 @@ static void flexcan_irq_state(struct net_device *dev, u32 reg_esr)
 	if (likely(new_state == priv->can.state))
 		return;
 
+	timestamp = priv->read(&regs->timer) << 16;
+
 	skb = alloc_can_err_skb(dev, &cf);
 	if (unlikely(!skb))
 		return;
-- 
2.26.2