openwrt/target/linux/layerscape/patches-5.4/802-can-0008-can-flexcan-flexcan_irq_state-only-read-timestamp-if.patch

From 1a92e5a9109963e2491eec111b84b35b4e2adc8f Mon Sep 17 00:00:00 2001
From: Marc Kleine-Budde <mkl@pengutronix.de>
Date: Wed, 9 Oct 2019 15:15:37 +0200
Subject: [PATCH] can: flexcan: flexcan_irq_state(): only read timestamp if
 needed

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>
---
 drivers/net/can/flexcan.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/net/can/flexcan.c
+++ b/drivers/net/can/flexcan.c
@@ -751,8 +751,6 @@ static void flexcan_irq_state(struct net
 	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) ?
@@ -772,6 +770,8 @@ static void flexcan_irq_state(struct net
 	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;