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ptp_qoriq: fix overflow in ptp_qoriq_adjfine() u64 calcalation

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Current calculation for diff of TMR_ADD register value may have
64-bit overflow in this code line, when long type scaled_ppm is
large.

adj *= scaled_ppm;

This patch is to resolve it by using mul_u64_u64_div_u64().

Signed-off-by: Yangbo Lu <yangbo.lu@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Yangbo Lu 2021-03-23 16:02:29 +08:00 committed by David S. Miller
parent 6ab4c3117a
commit f51d7bf1db
1 changed files with 7 additions and 6 deletions
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13
drivers/ptp/ptp_qoriq.c
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@ -189,15 +189,16 @@ int ptp_qoriq_adjfine(struct ptp_clock_info *ptp, long scaled_ppm)
tmr_add = ptp_qoriq->tmr_add;
adj = tmr_add;
/* calculate diff as adj*(scaled_ppm/65536)/1000000
* and round() to the nearest integer
/*
* Calculate diff and round() to the nearest integer
*
* diff = adj * (ppb / 1000000000)
* = adj * scaled_ppm / 65536000000
*/
adj *= scaled_ppm;
diff = div_u64(adj, 8000000);
diff = (diff >> 13) + ((diff >> 12) & 1);
diff = mul_u64_u64_div_u64(adj, scaled_ppm, 32768000000);
diff = DIV64_U64_ROUND_UP(diff, 2);
tmr_add = neg_adj ? tmr_add - diff : tmr_add + diff;
ptp_qoriq->write(&regs->ctrl_regs->tmr_add, tmr_add);
return 0;