netdev - [PATCH net 2/8] can: sja1000: fix max irq loop handling

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Message-ID: <20251126155713.217105-3-mkl@pengutronix.de>
Date: Wed, 26 Nov 2025 16:41:12 +0100
From: Marc Kleine-Budde <mkl@...gutronix.de>
To: netdev@...r.kernel.org
Cc: davem@...emloft.net,
	kuba@...nel.org,
	linux-can@...r.kernel.org,
	kernel@...gutronix.de,
	Thomas Mühlbacher <tmuehlbacher@...teo.net>,
	stable@...r.kernel.org,
	Oliver Hartkopp <socketcan@...tkopp.net>,
	Marc Kleine-Budde <mkl@...gutronix.de>
Subject: [PATCH net 2/8] can: sja1000: fix max irq loop handling

From: Thomas Mühlbacher <tmuehlbacher@...teo.net>

Reading the interrupt register `SJA1000_IR` causes all of its bits to be
reset. If we ever reach the condition of handling more than
`SJA1000_MAX_IRQ` IRQs, we will have read the register and reset all its
bits but without actually handling the interrupt inside of the loop
body.

This may, among other issues, cause us to never `netif_wake_queue()`
again after a transmission interrupt.

Fixes: 429da1cc841b ("can: Driver for the SJA1000 CAN controller")
Cc: stable@...r.kernel.org
Signed-off-by: Thomas Mühlbacher <tmuehlbacher@...teo.net>
Acked-by: Oliver Hartkopp <socketcan@...tkopp.net>
Link: https://patch.msgid.link/20251115153437.11419-1-tmuehlbacher@posteo.net
Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de>
---
 drivers/net/can/sja1000/sja1000.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/can/sja1000/sja1000.c b/drivers/net/can/sja1000/sja1000.c
index 4d245857ef1c..83476af8adb5 100644
--- a/drivers/net/can/sja1000/sja1000.c
+++ b/drivers/net/can/sja1000/sja1000.c
@@ -548,8 +548,8 @@ irqreturn_t sja1000_interrupt(int irq, void *dev_id)
 	if (priv->read_reg(priv, SJA1000_IER) == IRQ_OFF)
 		goto out;
 
-	while ((isrc = priv->read_reg(priv, SJA1000_IR)) &&
-	       (n < SJA1000_MAX_IRQ)) {
+	while ((n < SJA1000_MAX_IRQ) &&
+	       (isrc = priv->read_reg(priv, SJA1000_IR))) {
 
 		status = priv->read_reg(priv, SJA1000_SR);
 		/* check for absent controller due to hw unplug */
-- 
2.51.0