3 files changed, 20 insertions, 4 deletions
diff --git a/drivers/net/can/sja1000/sja1000.c b/drivers/net/can/sja1000/sja1000.c
index 24b58619f7c1..85f7cbfe8e5f 100644
--- a/drivers/net/can/sja1000/sja1000.c
+++ b/drivers/net/can/sja1000/sja1000.c
@@ -83,6 +83,20 @@ static struct can_bittiming_const sja1000_bittiming_const = {
 	.brp_inc = 1,
 };
 
+static void sja1000_write_cmdreg(struct sja1000_priv *priv, u8 val)
+{
+	unsigned long flags;
+
+	/*
+	 * The command register needs some locking and time to settle
+	 * the write_reg() operation - especially on SMP systems.
+	 */
+	spin_lock_irqsave(&priv->cmdreg_lock, flags);
+	priv->write_reg(priv, REG_CMR, val);
+	priv->read_reg(priv, REG_SR);
+	spin_unlock_irqrestore(&priv->cmdreg_lock, flags);
+}
+
 static int sja1000_probe_chip(struct net_device *dev)
 {
 	struct sja1000_priv *priv = netdev_priv(dev);
@@ -294,7 +308,7 @@ static netdev_tx_t sja1000_start_xmit(struct sk_buff *skb,
 
 	can_put_echo_skb(skb, dev, 0);
 
-	priv->write_reg(priv, REG_CMR, CMD_TR);
+	sja1000_write_cmdreg(priv, CMD_TR);
 
 	return NETDEV_TX_OK;
 }
@@ -343,7 +357,7 @@ static void sja1000_rx(struct net_device *dev)
 	cf->can_id = id;
 
 	/* release receive buffer */
-	priv->write_reg(priv, REG_CMR, CMD_RRB);
+	sja1000_write_cmdreg(priv, CMD_RRB);
 
 	netif_rx(skb);
 
@@ -371,7 +385,7 @@ static int sja1000_err(struct net_device *dev, uint8_t isrc, uint8_t status)
 		cf->data[1] = CAN_ERR_CRTL_RX_OVERFLOW;
 		stats->rx_over_errors++;
 		stats->rx_errors++;
-		priv->write_reg(priv, REG_CMR, CMD_CDO);	/* clear bit */
+		sja1000_write_cmdreg(priv, CMD_CDO);	/* clear bit */
 	}
 
 	if (isrc & IRQ_EI) {
diff --git a/drivers/net/can/sja1000/sja1000.h b/drivers/net/can/sja1000/sja1000.h
index 97a622b9302f..de8e778f6832 100644
--- a/drivers/net/can/sja1000/sja1000.h
+++ b/drivers/net/can/sja1000/sja1000.h
@@ -167,6 +167,7 @@ struct sja1000_priv {
 
 	void __iomem *reg_base;	 /* ioremap'ed address to registers */
 	unsigned long irq_flags; /* for request_irq() */
+	spinlock_t cmdreg_lock;  /* lock for concurrent cmd register writes */
 
 	u16 flags;		/* custom mode flags */
 	u8 ocr;			/* output control register */
diff --git a/drivers/net/can/sja1000/sja1000_platform.c b/drivers/net/can/sja1000/sja1000_platform.c
index b65cabb361ab..d9fadc489b32 100644
--- a/drivers/net/can/sja1000/sja1000_platform.c
+++ b/drivers/net/can/sja1000/sja1000_platform.c
@@ -111,7 +111,8 @@ static int sp_probe(struct platform_device *pdev)
 	dev->irq = res_irq->start;
 	priv->irq_flags = res_irq->flags & (IRQF_TRIGGER_MASK | IRQF_SHARED);
 	priv->reg_base = addr;
-	priv->can.clock.freq = pdata->clock;
+	/* The CAN clock frequency is half the oscillator clock frequency */
+	priv->can.clock.freq = pdata->osc_freq / 2;
 	priv->ocr = pdata->ocr;
 	priv->cdr = pdata->cdr;