net: dsa: mv88e6xxx: expose switch time as a PTP hardware clock

This patch adds basic support for exposing the 32-bit timestamp counter
inside the mv88e6xxx switch as a ptp_clock.

Adjfine implemented by Richard Cochran.
Andrew Lunn: fix return value of PTP stub function.

Signed-off-by: Brandon Streiff <brandon.streiff@ni.com>
Signed-off-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/mv88e6xxx/ptp.c

@@ -0,0 +1,197 @@
+/*
+ * Marvell 88E6xxx Switch PTP support
+ *
+ * Copyright (c) 2008 Marvell Semiconductor
+ *
+ * Copyright (c) 2017 National Instruments
+ *      Erik Hons <erik.hons@ni.com>
+ *      Brandon Streiff <brandon.streiff@ni.com>
+ *      Dane Wagner <dane.wagner@ni.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#include "chip.h"
+#include "global2.h"
+#include "ptp.h"
+
+/* Raw timestamps are in units of 8-ns clock periods. */
+#define CC_SHIFT	28
+#define CC_MULT		(8 << CC_SHIFT)
+#define CC_MULT_NUM	(1 << 9)
+#define CC_MULT_DEM	15625ULL
+
+#define TAI_EVENT_WORK_INTERVAL msecs_to_jiffies(100)
+
+#define cc_to_chip(cc) container_of(cc, struct mv88e6xxx_chip, tstamp_cc)
+#define ptp_to_chip(ptp) container_of(ptp, struct mv88e6xxx_chip, \
+				      ptp_clock_info)
+#define dw_overflow_to_chip(dw) container_of(dw, struct mv88e6xxx_chip, \
+					     overflow_work)
+
+static int mv88e6xxx_tai_read(struct mv88e6xxx_chip *chip, int addr,
+			      u16 *data, int len)
+{
+	if (!chip->info->ops->avb_ops->tai_read)
+		return -EOPNOTSUPP;
+
+	return chip->info->ops->avb_ops->tai_read(chip, addr, data, len);
+}
+
+static u64 mv88e6xxx_ptp_clock_read(const struct cyclecounter *cc)
+{
+	struct mv88e6xxx_chip *chip = cc_to_chip(cc);
+	u16 phc_time[2];
+	int err;
+
+	err = mv88e6xxx_tai_read(chip, MV88E6XXX_TAI_TIME_LO, phc_time,
+				 ARRAY_SIZE(phc_time));
+	if (err)
+		return 0;
+	else
+		return ((u32)phc_time[1] << 16) | phc_time[0];
+}
+
+static int mv88e6xxx_ptp_adjfine(struct ptp_clock_info *ptp, long scaled_ppm)
+{
+	struct mv88e6xxx_chip *chip = ptp_to_chip(ptp);
+	int neg_adj = 0;
+	u32 diff, mult;
+	u64 adj;
+
+	if (scaled_ppm < 0) {
+		neg_adj = 1;
+		scaled_ppm = -scaled_ppm;
+	}
+	mult = CC_MULT;
+	adj = CC_MULT_NUM;
+	adj *= scaled_ppm;
+	diff = div_u64(adj, CC_MULT_DEM);
+
+	mutex_lock(&chip->reg_lock);
+
+	timecounter_read(&chip->tstamp_tc);
+	chip->tstamp_cc.mult = neg_adj ? mult - diff : mult + diff;
+
+	mutex_unlock(&chip->reg_lock);
+
+	return 0;
+}
+
+static int mv88e6xxx_ptp_adjtime(struct ptp_clock_info *ptp, s64 delta)
+{
+	struct mv88e6xxx_chip *chip = ptp_to_chip(ptp);
+
+	mutex_lock(&chip->reg_lock);
+	timecounter_adjtime(&chip->tstamp_tc, delta);
+	mutex_unlock(&chip->reg_lock);
+
+	return 0;
+}
+
+static int mv88e6xxx_ptp_gettime(struct ptp_clock_info *ptp,
+				 struct timespec64 *ts)
+{
+	struct mv88e6xxx_chip *chip = ptp_to_chip(ptp);
+	u64 ns;
+
+	mutex_lock(&chip->reg_lock);
+	ns = timecounter_read(&chip->tstamp_tc);
+	mutex_unlock(&chip->reg_lock);
+
+	*ts = ns_to_timespec64(ns);
+
+	return 0;
+}
+
+static int mv88e6xxx_ptp_settime(struct ptp_clock_info *ptp,
+				 const struct timespec64 *ts)
+{
+	struct mv88e6xxx_chip *chip = ptp_to_chip(ptp);
+	u64 ns;
+
+	ns = timespec64_to_ns(ts);
+
+	mutex_lock(&chip->reg_lock);
+	timecounter_init(&chip->tstamp_tc, &chip->tstamp_cc, ns);
+	mutex_unlock(&chip->reg_lock);
+
+	return 0;
+}
+
+static int mv88e6xxx_ptp_enable(struct ptp_clock_info *ptp,
+				struct ptp_clock_request *rq, int on)
+{
+	return -EOPNOTSUPP;
+}
+
+static int mv88e6xxx_ptp_verify(struct ptp_clock_info *ptp, unsigned int pin,
+				enum ptp_pin_function func, unsigned int chan)
+{
+	return -EOPNOTSUPP;
+}
+
+/* With a 125MHz input clock, the 32-bit timestamp counter overflows in ~34.3
+ * seconds; this task forces periodic reads so that we don't miss any.
+ */
+#define MV88E6XXX_TAI_OVERFLOW_PERIOD (HZ * 16)
+static void mv88e6xxx_ptp_overflow_check(struct work_struct *work)
+{
+	struct delayed_work *dw = to_delayed_work(work);
+	struct mv88e6xxx_chip *chip = dw_overflow_to_chip(dw);
+	struct timespec64 ts;
+
+	mv88e6xxx_ptp_gettime(&chip->ptp_clock_info, &ts);
+
+	schedule_delayed_work(&chip->overflow_work,
+			      MV88E6XXX_TAI_OVERFLOW_PERIOD);
+}
+
+int mv88e6xxx_ptp_setup(struct mv88e6xxx_chip *chip)
+{
+	/* Set up the cycle counter */
+	memset(&chip->tstamp_cc, 0, sizeof(chip->tstamp_cc));
+	chip->tstamp_cc.read	= mv88e6xxx_ptp_clock_read;
+	chip->tstamp_cc.mask	= CYCLECOUNTER_MASK(32);
+	chip->tstamp_cc.mult	= CC_MULT;
+	chip->tstamp_cc.shift	= CC_SHIFT;
+
+	timecounter_init(&chip->tstamp_tc, &chip->tstamp_cc,
+			 ktime_to_ns(ktime_get_real()));
+
+	INIT_DELAYED_WORK(&chip->overflow_work, mv88e6xxx_ptp_overflow_check);
+
+	chip->ptp_clock_info.owner = THIS_MODULE;
+	snprintf(chip->ptp_clock_info.name, sizeof(chip->ptp_clock_info.name),
+		 dev_name(chip->dev));
+	chip->ptp_clock_info.max_adj	= 1000000;
+
+	chip->ptp_clock_info.adjfine	= mv88e6xxx_ptp_adjfine;
+	chip->ptp_clock_info.adjtime	= mv88e6xxx_ptp_adjtime;
+	chip->ptp_clock_info.gettime64	= mv88e6xxx_ptp_gettime;
+	chip->ptp_clock_info.settime64	= mv88e6xxx_ptp_settime;
+	chip->ptp_clock_info.enable	= mv88e6xxx_ptp_enable;
+	chip->ptp_clock_info.verify	= mv88e6xxx_ptp_verify;
+
+	chip->ptp_clock = ptp_clock_register(&chip->ptp_clock_info, chip->dev);
+	if (IS_ERR(chip->ptp_clock))
+		return PTR_ERR(chip->ptp_clock);
+
+	schedule_delayed_work(&chip->overflow_work,
+			      MV88E6XXX_TAI_OVERFLOW_PERIOD);
+
+	return 0;
+}
+
+void mv88e6xxx_ptp_free(struct mv88e6xxx_chip *chip)
+{
+	if (chip->ptp_clock) {
+		cancel_delayed_work_sync(&chip->overflow_work);
+
+		ptp_clock_unregister(chip->ptp_clock);
+		chip->ptp_clock = NULL;
+	}
+}