On Mon, Oct 19, 2020 at 07:24:34PM +0200, Christian Eggers wrote:

 static int ksz9477_ptp_enable(struct ptp_clock_info *ptp, struct ptp_clock_request *req, int on)
 {
-	return -ENOTTY;
+	struct ksz_device *dev = container_of(ptp, struct ksz_device, ptp_caps);
+	int ret;
+
+	switch (req->type) {
+	case PTP_CLK_REQ_PPS:
+		mutex_lock(&dev->ptp_mutex);
+		ret = ksz9477_ptp_enable_pps(dev, on);
+		mutex_unlock(&dev->ptp_mutex);
+		return ret;
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
 }

Nope, this is not what you're looking for. Please implement
PTP_CLK_REQ_PEROUT.