On Tue, Mar 23, 2021 at 04:02:29PM +0800, Yangbo Lu wrote: > 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...@nxp.com> > Acked-by: Richard Cochran <richardcoch...@gmail.com> > --- > drivers/ptp/ptp_qoriq.c | 13 +++++++------ > 1 file changed, 7 insertions(+), 6 deletions(-) > > diff --git a/drivers/ptp/ptp_qoriq.c b/drivers/ptp/ptp_qoriq.c > index 68beb1bd07c0..f7f220700cb5 100644 > --- a/drivers/ptp/ptp_qoriq.c > +++ b/drivers/ptp/ptp_qoriq.c > @@ -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);
mul_u64_u64_div_u64() is not exported. As result, every build with CONFIG_PTP_1588_CLOCK_QORIQ=m (ie every allmodconfig build) fails with: ERROR: modpost: "mul_u64_u64_div_u64" [drivers/ptp/ptp-qoriq.ko] undefined! or a similar error. Guenter
