ptp: ocp: Add ptp_ocp_adjtime_coarse for large adjustments

In ("ptp: ocp: Have FPGA fold in ns adjustment for adjtime."), the
ns adjustment was written to the FPGA register, so the clock could
accurately perform adjustments.

However, the adjtime() call passes in a s64, while the clock adjustment
registers use a s32.  When trying to perform adjustments with a large
value (37 sec), things fail.

Examine the incoming delta, and if larger than 1 sec, use the original
(coarse) adjustment method.  If smaller than 1 sec, then allow the
FPGA to fold in the changes over a 1 second window.

Fixes: 6d59d4fa ("ptp: ocp: Have FPGA fold in ns adjustment for adjtime.")
Signed-off-by: Jonathan Lemon <jonathan.lemon@gmail.com>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Link: https://lore.kernel.org/r/20220228203957.367371-1-jonathan.lemon@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/ptp/ptp_ocp.c

@@ -607,7 +607,7 @@ ptp_ocp_settime(struct ptp_clock_info *ptp_info, const struct timespec64 *ts)
 }
 
 static void
-__ptp_ocp_adjtime_locked(struct ptp_ocp *bp, u64 adj_val)
+__ptp_ocp_adjtime_locked(struct ptp_ocp *bp, u32 adj_val)
 {
 	u32 select, ctrl;
 
@@ -615,7 +615,7 @@ __ptp_ocp_adjtime_locked(struct ptp_ocp *bp, u64 adj_val)
 	iowrite32(OCP_SELECT_CLK_REG, &bp->reg->select);
 
 	iowrite32(adj_val, &bp->reg->offset_ns);
-	iowrite32(adj_val & 0x7f, &bp->reg->offset_window_ns);
+	iowrite32(NSEC_PER_SEC, &bp->reg->offset_window_ns);
 
 	ctrl = OCP_CTRL_ADJUST_OFFSET | OCP_CTRL_ENABLE;
 	iowrite32(ctrl, &bp->reg->ctrl);
@@ -624,6 +624,22 @@ __ptp_ocp_adjtime_locked(struct ptp_ocp *bp, u64 adj_val)
 	iowrite32(select >> 16, &bp->reg->select);
 }
 
+static void
+ptp_ocp_adjtime_coarse(struct ptp_ocp *bp, u64 delta_ns)
+{
+	struct timespec64 ts;
+	unsigned long flags;
+	int err;
+
+	spin_lock_irqsave(&bp->lock, flags);
+	err = __ptp_ocp_gettime_locked(bp, &ts, NULL);
+	if (likely(!err)) {
+		timespec64_add_ns(&ts, delta_ns);
+		__ptp_ocp_settime_locked(bp, &ts);
+	}
+	spin_unlock_irqrestore(&bp->lock, flags);
+}
+
 static int
 ptp_ocp_adjtime(struct ptp_clock_info *ptp_info, s64 delta_ns)
 {
@@ -631,6 +647,11 @@ ptp_ocp_adjtime(struct ptp_clock_info *ptp_info, s64 delta_ns)
 	unsigned long flags;
 	u32 adj_ns, sign;
 
+	if (delta_ns > NSEC_PER_SEC || -delta_ns > NSEC_PER_SEC) {
+		ptp_ocp_adjtime_coarse(bp, delta_ns);
+		return 0;
+	}
+
 	sign = delta_ns < 0 ? BIT(31) : 0;
 	adj_ns = sign ? -delta_ns : delta_ns;