@@ -2414,6 +2414,22 @@ static int sh_eth_start_xmit(struct sk_buff *skb, struct net_device *ndev)
return NETDEV_TX_OK;
}
+/* The statistics registers have write-clear behaviour, which means we
+ * will lose any increment between the read and write. We mitigate
+ * this by only clearing when we read a non-zero value, so we will
+ * never falsely report a total of zero.
+ */
+static void
+sh_eth_update_stat(struct net_device *ndev, unsigned long *stat, int reg)
+{
+ u32 delta = sh_eth_read(ndev, reg);
+
+ if (delta) {
+ *stat += delta;
+ sh_eth_write(ndev, 0, reg);
+ }
+}
+
static struct net_device_stats *sh_eth_get_stats(struct net_device *ndev)
{
struct sh_eth_private *mdp = netdev_priv(ndev);
@@ -2424,21 +2440,18 @@ static struct net_device_stats *sh_eth_get_stats(struct net_device *ndev)
if (!mdp->is_opened)
return &ndev->stats;
- ndev->stats.tx_dropped += sh_eth_read(ndev, TROCR);
- sh_eth_write(ndev, 0, TROCR); /* (write clear) */
- ndev->stats.collisions += sh_eth_read(ndev, CDCR);
- sh_eth_write(ndev, 0, CDCR); /* (write clear) */
- ndev->stats.tx_carrier_errors += sh_eth_read(ndev, LCCR);
- sh_eth_write(ndev, 0, LCCR); /* (write clear) */
+ sh_eth_update_stat(ndev, &ndev->stats.tx_dropped, TROCR);
+ sh_eth_update_stat(ndev, &ndev->stats.collisions, CDCR);
+ sh_eth_update_stat(ndev, &ndev->stats.tx_carrier_errors, LCCR);
if (sh_eth_is_gether(mdp)) {
- ndev->stats.tx_carrier_errors += sh_eth_read(ndev, CERCR);
- sh_eth_write(ndev, 0, CERCR); /* (write clear) */
- ndev->stats.tx_carrier_errors += sh_eth_read(ndev, CEECR);
- sh_eth_write(ndev, 0, CEECR); /* (write clear) */
+ sh_eth_update_stat(ndev, &ndev->stats.tx_carrier_errors,
+ CERCR);
+ sh_eth_update_stat(ndev, &ndev->stats.tx_carrier_errors,
+ CEECR);
} else {
- ndev->stats.tx_carrier_errors += sh_eth_read(ndev, CNDCR);
- sh_eth_write(ndev, 0, CNDCR); /* (write clear) */
+ sh_eth_update_stat(ndev, &ndev->stats.tx_carrier_errors,
+ CNDCR);
}
return &ndev->stats;
The statistics registers have write-clear behaviour, which means we will lose any increment between the read and write. Mitigate this by only clearing when we read a non-zero value, so we will never falsely report a total of zero. This also saves time as we only handle error statistics here and they won't often be incremented. Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk> --- drivers/net/ethernet/renesas/sh_eth.c | 37 ++++++++++++++++++++++----------- 1 file changed, 25 insertions(+), 12 deletions(-)