ptp: ocp: Have FPGA fold in ns adjustment for adjtime.

The current implementation of adjtime uses gettime/settime to
perform nanosecond adjustments.  This introduces addtional phase
errors due to delays.

Instead, use the FPGA's ability to just apply the nanosecond
adjustment to the clock directly.
Signed-off-by: Jonathan Lemon <jonathan.lemon@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/ptp/ptp_ocp.c

@@ -594,9 +594,6 @@ ptp_ocp_settime(struct ptp_clock_info *ptp_info, const struct timespec64 *ts)
 	struct ptp_ocp *bp = container_of(ptp_info, struct ptp_ocp, ptp_info);
 	unsigned long flags;
 
-	if (ioread32(&bp->reg->status) & OCP_STATUS_IN_SYNC)
-		return 0;
-
 	spin_lock_irqsave(&bp->lock, flags);
 	__ptp_ocp_settime_locked(bp, ts);
 	spin_unlock_irqrestore(&bp->lock, flags);
@@ -604,26 +601,39 @@ ptp_ocp_settime(struct ptp_clock_info *ptp_info, const struct timespec64 *ts)
 	return 0;
 }
 
+static void
+__ptp_ocp_adjtime_locked(struct ptp_ocp *bp, u64 adj_val)
+{
+	u32 select, ctrl;
+
+	select = ioread32(&bp->reg->select);
+	iowrite32(OCP_SELECT_CLK_REG, &bp->reg->select);
+
+	iowrite32(adj_val, &bp->reg->offset_ns);
+	iowrite32(adj_val & 0x7f, &bp->reg->offset_window_ns);
+
+	ctrl = OCP_CTRL_ADJUST_OFFSET | OCP_CTRL_ENABLE;
+	iowrite32(ctrl, &bp->reg->ctrl);
+
+	/* restore clock selection */
+	iowrite32(select >> 16, &bp->reg->select);
+}
+
 static int
 ptp_ocp_adjtime(struct ptp_clock_info *ptp_info, s64 delta_ns)
 {
 	struct ptp_ocp *bp = container_of(ptp_info, struct ptp_ocp, ptp_info);
-	struct timespec64 ts;
 	unsigned long flags;
-	int err;
+	u32 adj_ns, sign;
 
-	if (ioread32(&bp->reg->status) & OCP_STATUS_IN_SYNC)
-		return 0;
+	sign = delta_ns < 0 ? BIT(31) : 0;
+	adj_ns = sign ? -delta_ns : delta_ns;
 
 	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);
-	}
+	__ptp_ocp_adjtime_locked(bp, sign | adj_ns);
 	spin_unlock_irqrestore(&bp->lock, flags);
 
-	return err;
+	return 0;
 }
 
 static int
@@ -636,7 +646,7 @@ ptp_ocp_null_adjfine(struct ptp_clock_info *ptp_info, long scaled_ppm)
 }
 
 static int
-ptp_ocp_adjphase(struct ptp_clock_info *ptp_info, s32 phase_ns)
+ptp_ocp_null_adjphase(struct ptp_clock_info *ptp_info, s32 phase_ns)
 {
 	return -EOPNOTSUPP;
 }
@@ -699,7 +709,7 @@ static const struct ptp_clock_info ptp_ocp_clock_info = {
 	.settime64	= ptp_ocp_settime,
 	.adjtime	= ptp_ocp_adjtime,
 	.adjfine	= ptp_ocp_null_adjfine,
-	.adjphase	= ptp_ocp_adjphase,
+	.adjphase	= ptp_ocp_null_adjphase,
 	.enable		= ptp_ocp_enable,
 	.pps		= true,
 	.n_ext_ts	= 4,