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 <rmk+kernel@armlinux.org.uk> Reviewed-by: Andrew Lunn <andrew@lunn.ch> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -1381,6 +1381,7 @@ static unsigned int get_rx_coal(struct mv643xx_eth_private *mp)
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temp = (val & 0x003fff00) >> 8;
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temp *= 64000000;
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temp += mp->t_clk / 2;
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do_div(temp, mp->t_clk);
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return (unsigned int)temp;
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@ -1417,6 +1418,7 @@ static unsigned int get_tx_coal(struct mv643xx_eth_private *mp)
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temp = (rdlp(mp, TX_FIFO_URGENT_THRESHOLD) & 0x3fff0) >> 4;
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temp *= 64000000;
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temp += mp->t_clk / 2;
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do_div(temp, mp->t_clk);
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return (unsigned int)temp;
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