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stmmac: fix signed 64-bit division

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I link error on 32-bit ARM points to yet another arithmetic bug:

drivers/net/ethernet/stmicro/stmmac/stmmac_tc.o: In function `tc_setup_cbs':
stmmac_tc.c:(.text+0x148): undefined reference to `__aeabi_uldivmod'
stmmac_tc.c:(.text+0x1fc): undefined reference to `__aeabi_uldivmod'
stmmac_tc.c:(.text+0x308): undefined reference to `__aeabi_uldivmod'
stmmac_tc.c:(.text+0x320): undefined reference to `__aeabi_uldivmod'
stmmac_tc.c:(.text+0x33c): undefined reference to `__aeabi_uldivmod'
drivers/net/ethernet/stmicro/stmmac/stmmac_tc.o:stmmac_tc.c:(.text+0x3a4): more undefined references to `__aeabi_uldivmod' follow

I observe that the last change to add the 'ul' prefix was incorrect,
as it did not turn the result of the multiplication into a 64-bit
expression on 32-bit architectures. Further, it seems that the
do_div() macro gets confused by the fact that we pass a signed
variable rather than unsigned into it.

This changes the code to instead use the div_s64() helper that is
meant for signed division, along with changing the constant suffix
to 'll' to actually make it a 64-bit argument everywhere, fixing
both of the issues I pointed out.

I'm not completely convinced that this makes the code correct, but
I'm fairly sure that we have two problems less than before.

Fixes: 1f705bc61aee ("net: stmmac: Add support for CBS QDISC")
Fixes: c18a9c096683 ("net: stmmac_tc: use 64-bit arithmetic instead of 32-bit")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Arnd Bergmann 2018-07-06 15:36:07 +02:00 committed by David S. Miller
parent a4dc70d46c
commit 8f704ef666
1 changed files with 4 additions and 6 deletions
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10
drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c
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@ -321,18 +321,16 @@ static int tc_setup_cbs(struct stmmac_priv *priv,
speed_div = (priv->speed == SPEED_100) ? 100000 : 1000000;
/* Final adjustments for HW */
value = qopt->idleslope * 1024UL * ptr;
do_div(value, speed_div);
value = div_s64(qopt->idleslope * 1024ll * ptr, speed_div);
priv->plat->tx_queues_cfg[queue].idle_slope = value & GENMASK(31, 0);
value = -qopt->sendslope * 1024UL * ptr;
do_div(value, speed_div);
value = div_s64(-qopt->sendslope * 1024ll * ptr, speed_div);
priv->plat->tx_queues_cfg[queue].send_slope = value & GENMASK(31, 0);
value = qopt->hicredit * 1024UL * 8;
value = qopt->hicredit * 1024ll * 8;
priv->plat->tx_queues_cfg[queue].high_credit = value & GENMASK(31, 0);
value = qopt->locredit * 1024UL * 8;
value = qopt->locredit * 1024ll * 8;
priv->plat->tx_queues_cfg[queue].low_credit = value & GENMASK(31, 0);
ret = stmmac_config_cbs(priv, priv->hw,