| Message ID | E1c1Wdl-0000tO-Ql@rmk-PC.armlinux.org.uk |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
On Tue, Nov 01, 2016 at 10:50:01AM +0000, Russell King wrote: > 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 <rmk+kernel@armlinux.org.uk> Reviewed-by: Andrew Lunn <andrew@lunn.ch> Andrew
From: Russell King <rmk+kernel@armlinux.org.uk> Date: Tue, 01 Nov 2016 10:50:01 +0000 > 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 <rmk+kernel@armlinux.org.uk> Applied, thanks.
diff --git a/drivers/net/ethernet/marvell/mv643xx_eth.c b/drivers/net/ethernet/marvell/mv643xx_eth.c index 2a85202de6da..8a472cbfda09 100644 --- a/drivers/net/ethernet/marvell/mv643xx_eth.c +++ b/drivers/net/ethernet/marvell/mv643xx_eth.c @@ -1429,6 +1429,7 @@ 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; @@ -1465,6 +1466,7 @@ 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;
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 <rmk+kernel@armlinux.org.uk> --- drivers/net/ethernet/marvell/mv643xx_eth.c | 2 ++ 1 file changed, 2 insertions(+)