Commit f51d7bf1 authored by Yangbo Lu's avatar Yangbo Lu Committed by David S. Miller
Browse files

ptp_qoriq: fix overflow in ptp_qoriq_adjfine() u64 calcalation 



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: default avatarYangbo Lu <yangbo.lu@nxp.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 6ab4c311

drivers/ptp/ptp_qoriq.c

+7 −6
Original line number Diff line number Diff line
@@ -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;