[PATCH] net: macb: Fix ptp time adjustment for large negative delta

When delta passed to gem_ptp_adjtime is negative, the sign is
maintained in the ns_to_timespec64 conversion. Hence timespec_add
should be used directly. timespec_sub will just subtract the negative
value thus increasing the time difference.

Signed-off-by: Harini Katakam <redacted>
---
 drivers/net/ethernet/cadence/macb_ptp.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/cadence/macb_ptp.c b/drivers/net/ethernet/cadence/macb_ptp.c
index 2220c77..6788351 100644
--- a/drivers/net/ethernet/cadence/macb_ptp.c
+++ b/drivers/net/ethernet/cadence/macb_ptp.c

@@ -170,10 +170,7 @@ static int gem_ptp_adjtime(struct ptp_clock_info *ptp, s64 delta)
 
 	if (delta > TSU_NSEC_MAX_VAL) {
 		gem_tsu_get_time(&bp->ptp_clock_info, &now);
-		if (sign)
-			now = timespec64_sub(now, then);
-		else
-			now = timespec64_add(now, then);
+		now = timespec64_add(now, then);
 
 		gem_tsu_set_time(&bp->ptp_clock_info,
 				 (const struct timespec64 *)&now);

-- 
2.7.4

On 20/06/2018 at 13:34, Harini Katakam wrote:

When delta passed to gem_ptp_adjtime is negative, the sign is
maintained in the ns_to_timespec64 conversion. Hence timespec_add
should be used directly. timespec_sub will just subtract the negative
value thus increasing the time difference.

Signed-off-by: Harini Katakam <redacted>

Makes sense:
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>

-- 
Nicolas Ferre

From: Harini Katakam <redacted>
Date: Wed, 20 Jun 2018 17:04:20 +0530

When delta passed to gem_ptp_adjtime is negative, the sign is
maintained in the ns_to_timespec64 conversion. Hence timespec_add
should be used directly. timespec_sub will just subtract the negative
value thus increasing the time difference.

Signed-off-by: Harini Katakam <redacted>

Applied and queued up for -stable.