From b9b84fc07dbc6ac74d85f1b1a401b41c403fecb1 Mon Sep 17 00:00:00 2001 From: Russell King Date: Tue, 1 Nov 2016 10:50:01 +0000 Subject: net: mv643xx_eth: ensure coalesce settings survive read-modify-write The coalesce settings behave badly when changing just one value: ... # ethtool -c eth0 rx-usecs: 249 ... # ethtool -C eth0 tx-usecs 250 ... # ethtool -c eth0 rx-usecs: 248 This occurs due to rounding errors when calculating the microseconds value - the divisons round down. This causes (eg) the rx-usecs to decrease by one every time the tx-usecs value is set as per the above. Fix this by making the divison round-to-nearest. Signed-off-by: Russell King Reviewed-by: Andrew Lunn Signed-off-by: David S. Miller --- drivers/net/ethernet/marvell/mv643xx_eth.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/net/ethernet/marvell/mv643xx_eth.c b/drivers/net/ethernet/marvell/mv643xx_eth.c index bf5cc55ba24c..5b12022adf1f 100644 --- a/drivers/net/ethernet/marvell/mv643xx_eth.c +++ b/drivers/net/ethernet/marvell/mv643xx_eth.c @@ -1381,6 +1381,7 @@ static unsigned int get_rx_coal(struct mv643xx_eth_private *mp) temp = (val & 0x003fff00) >> 8; temp *= 64000000; + temp += mp->t_clk / 2; do_div(temp, mp->t_clk); return (unsigned int)temp; @@ -1417,6 +1418,7 @@ static unsigned int get_tx_coal(struct mv643xx_eth_private *mp) temp = (rdlp(mp, TX_FIFO_URGENT_THRESHOLD) & 0x3fff0) >> 4; temp *= 64000000; + temp += mp->t_clk / 2; do_div(temp, mp->t_clk); return (unsigned int)temp; -- cgit v1.2.3