[PATCH net] ptp: ocp: have adjtime handle negative delta_ns correctly

[Jonathan Lemon <jonathan.lemon@gmail.com>]

delta_ns is a s64, but it was being passed ptp_ocp_adjtime_coarse
as an u64.  Also, it turns out that timespec64_add_ns() only handles
positive values, so the math needs to be updated.

Fix by passing in the correct signed value, then adding to a
nanosecond version of the timespec.

Fixes: '90f8f4c0e3ce ("ptp: ocp: Add ptp_ocp_adjtime_coarse for large adjustments")'
Signed-off-by: Jonathan Lemon <jonathan.lemon@gmail.com>
---
 drivers/ptp/ptp_ocp.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/ptp/ptp_ocp.c b/drivers/ptp/ptp_ocp.c
index dd45471f6780..65e592ec272e 100644
--- a/drivers/ptp/ptp_ocp.c
+++ b/drivers/ptp/ptp_ocp.c
@@ -841,16 +841,18 @@ __ptp_ocp_adjtime_locked(struct ptp_ocp *bp, u32 adj_val)
 }
 
 static void
-ptp_ocp_adjtime_coarse(struct ptp_ocp *bp, u64 delta_ns)
+ptp_ocp_adjtime_coarse(struct ptp_ocp *bp, s64 delta_ns)
 {
 	struct timespec64 ts;
 	unsigned long flags;
 	int err;
+	s64 ns;
 
 	spin_lock_irqsave(&bp->lock, flags);
 	err = __ptp_ocp_gettime_locked(bp, &ts, NULL);
 	if (likely(!err)) {
-		timespec64_add_ns(&ts, delta_ns);
+		ns = timespec64_to_ns(&ts) + delta_ns;
+		ts = ns_to_timespec64(ns);
 		__ptp_ocp_settime_locked(bp, &ts);
 	}
 	spin_unlock_irqrestore(&bp->lock, flags);
-- 
2.31.1