net: dsa: sja1105: configure the PTP_CLK pin as EXT_TS or PER_OUT

The SJA1105 switch family has a PTP_CLK pin which emits a signal with
fixed 50% duty cycle, but variable frequency and programmable start time.

On the second generation (P/Q/R/S) switches, this pin supports even more
functionality. The use case described by the hardware documents talks
about synchronization via oneshot pulses: given 2 sja1105 switches,
arbitrarily designated as a master and a slave, the master emits a
single pulse on PTP_CLK, while the slave is configured to timestamp this
pulse received on its PTP_CLK pin (which must obviously be configured as
input). The difference between the timestamps then exactly becomes the
slave offset to the master.

The only trouble with the above is that the hardware is very much tied
into this use case only, and not very generic beyond that:
 - When emitting a oneshot pulse, instead of being told when to emit it,
   the switch just does it "now" and tells you later what time it was,
   via the PTPSYNCTS register. [ Incidentally, this is the same register
   that the slave uses to collect the ext_ts timestamp from, too. ]
 - On the sync slave, there is no interrupt mechanism on reception of a
   new extts, and no FIFO to buffer them, because in the foreseen use
   case, software is in control of both the master and the slave pins,
   so it "knows" when there's something to collect.

These 2 problems mean that:
 - We don't support (at least yet) the quirky oneshot mode exposed by
   the hardware, just normal periodic output.
 - We abuse the hardware a little bit when we expose generic extts.
   Because there's no interrupt mechanism, we need to poll at double the
   frequency we expect to receive a pulse. Currently that means a
   non-configurable "twice a second".

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 247 insertions, 0 deletions

diff --git a/drivers/net/dsa/sja1105/sja1105_ptp.c b/drivers/net/dsa/sja1105/sja1105_ptp.c
index a07aaf55068f..a22f8e3fc06b 100644
--- a/drivers/net/dsa/sja1105/sja1105_ptp.c
+++ b/drivers/net/dsa/sja1105/sja1105_ptp.c
@@ -14,6 +14,17 @@
 #define SJA1105_MAX_ADJ_PPB		32000000
 #define SJA1105_SIZE_PTP_CMD		4
 
+/* PTPSYNCTS has no interrupt or update mechanism, because the intended
+ * hardware use case is for the timestamp to be collected synchronously,
+ * immediately after the CAS_MASTER SJA1105 switch has triggered a CASSYNC
+ * pulse on the PTP_CLK pin. When used as a generic extts source, it needs
+ * polling and a comparison with the old value. The polling interval is just
+ * the Nyquist rate of a canonical PPS input (e.g. from a GPS module).
+ * Anything of higher frequency than 1 Hz will be lost, since there is no
+ * timestamp FIFO.
+ */
+#define SJA1105_EXTTS_INTERVAL		(HZ / 2)
+
 /*            This range is actually +/- SJA1105_MAX_ADJ_PPB
  *            divided by 1000 (ppb -> ppm) and with a 16-bit
  *            "fractional" part (actually fixed point).
@@ -39,6 +50,8 @@ enum sja1105_ptp_clk_mode {
 	PTP_SET_MODE = 0,
 };
 
+#define extts_to_data(d) \
+		container_of((d), struct sja1105_ptp_data, extts_work)
 #define ptp_caps_to_data(d) \
 		container_of((d), struct sja1105_ptp_data, caps)
 #define ptp_data_to_sja1105(d) \
@@ -168,6 +181,8 @@ void sja1105et_ptp_cmd_packing(u8 *buf, struct sja1105_ptp_cmd *cmd,
 	sja1105_packing(buf, &valid,           31, 31, size, op);
 	sja1105_packing(buf, &cmd->ptpstrtsch, 30, 30, size, op);
 	sja1105_packing(buf, &cmd->ptpstopsch, 29, 29, size, op);
+	sja1105_packing(buf, &cmd->startptpcp, 28, 28, size, op);
+	sja1105_packing(buf, &cmd->stopptpcp,  27, 27, size, op);
 	sja1105_packing(buf, &cmd->resptp,      2,  2, size, op);
 	sja1105_packing(buf, &cmd->corrclk4ts,  1,  1, size, op);
 	sja1105_packing(buf, &cmd->ptpclkadd,   0,  0, size, op);
@@ -183,6 +198,8 @@ void sja1105pqrs_ptp_cmd_packing(u8 *buf, struct sja1105_ptp_cmd *cmd,
 	sja1105_packing(buf, &valid,           31, 31, size, op);
 	sja1105_packing(buf, &cmd->ptpstrtsch, 30, 30, size, op);
 	sja1105_packing(buf, &cmd->ptpstopsch, 29, 29, size, op);
+	sja1105_packing(buf, &cmd->startptpcp, 28, 28, size, op);
+	sja1105_packing(buf, &cmd->stopptpcp,  27, 27, size, op);
 	sja1105_packing(buf, &cmd->resptp,      3,  3, size, op);
 	sja1105_packing(buf, &cmd->corrclk4ts,  2,  2, size, op);
 	sja1105_packing(buf, &cmd->ptpclkadd,   0,  0, size, op);
@@ -577,6 +594,227 @@ static int sja1105_ptp_adjtime(struct ptp_clock_info *ptp, s64 delta)
 	return rc;
 }
 
+static void sja1105_ptp_extts_work(struct work_struct *work)
+{
+	struct delayed_work *dw = to_delayed_work(work);
+	struct sja1105_ptp_data *ptp_data = extts_to_data(dw);
+	struct sja1105_private *priv = ptp_data_to_sja1105(ptp_data);
+	const struct sja1105_regs *regs = priv->info->regs;
+	struct ptp_clock_event event;
+	u64 ptpsyncts = 0;
+	int rc;
+
+	mutex_lock(&ptp_data->lock);
+
+	rc = sja1105_xfer_u64(priv, SPI_READ, regs->ptpsyncts, &ptpsyncts,
+			      NULL);
+	if (rc < 0)
+		dev_err_ratelimited(priv->ds->dev,
+				    "Failed to read PTPSYNCTS: %d\n", rc);
+
+	if (ptpsyncts && ptp_data->ptpsyncts != ptpsyncts) {
+		event.index = 0;
+		event.type = PTP_CLOCK_EXTTS;
+		event.timestamp = ns_to_ktime(sja1105_ticks_to_ns(ptpsyncts));
+		ptp_clock_event(ptp_data->clock, &event);
+
+		ptp_data->ptpsyncts = ptpsyncts;
+	}
+
+	mutex_unlock(&ptp_data->lock);
+
+	schedule_delayed_work(&ptp_data->extts_work, SJA1105_EXTTS_INTERVAL);
+}
+
+static int sja1105_change_ptp_clk_pin_func(struct sja1105_private *priv,
+					   enum ptp_pin_function func)
+{
+	struct sja1105_avb_params_entry *avb;
+	enum ptp_pin_function old_func;
+
+	avb = priv->static_config.tables[BLK_IDX_AVB_PARAMS].entries;
+
+	if (priv->info->device_id == SJA1105E_DEVICE_ID ||
+	    priv->info->device_id == SJA1105T_DEVICE_ID ||
+	    avb->cas_master)
+		old_func = PTP_PF_PEROUT;
+	else
+		old_func = PTP_PF_EXTTS;
+
+	if (func == old_func)
+		return 0;
+
+	avb->cas_master = (func == PTP_PF_PEROUT);
+
+	return sja1105_dynamic_config_write(priv, BLK_IDX_AVB_PARAMS, 0, avb,
+					    true);
+}
+
+/* The PTP_CLK pin may be configured to toggle with a 50% duty cycle and a
+ * frequency f:
+ *
+ *           NSEC_PER_SEC
+ * f = ----------------------
+ *     (PTPPINDUR * 8 ns) * 2
+ */
+static int sja1105_per_out_enable(struct sja1105_private *priv,
+				  struct ptp_perout_request *perout,
+				  bool on)
+{
+	struct sja1105_ptp_data *ptp_data = &priv->ptp_data;
+	const struct sja1105_regs *regs = priv->info->regs;
+	struct sja1105_ptp_cmd cmd = ptp_data->cmd;
+	int rc;
+
+	/* We only support one channel */
+	if (perout->index != 0)
+		return -EOPNOTSUPP;
+
+	/* Reject requests with unsupported flags */
+	if (perout->flags)
+		return -EOPNOTSUPP;
+
+	mutex_lock(&ptp_data->lock);
+
+	rc = sja1105_change_ptp_clk_pin_func(priv, PTP_PF_PEROUT);
+	if (rc)
+		goto out;
+
+	if (on) {
+		struct timespec64 pin_duration_ts = {
+			.tv_sec = perout->period.sec,
+			.tv_nsec = perout->period.nsec,
+		};
+		struct timespec64 pin_start_ts = {
+			.tv_sec = perout->start.sec,
+			.tv_nsec = perout->start.nsec,
+		};
+		u64 pin_duration = timespec64_to_ns(&pin_duration_ts);
+		u64 pin_start = timespec64_to_ns(&pin_start_ts);
+		u32 pin_duration32;
+		u64 now;
+
+		/* ptppindur: 32 bit register which holds the interval between
+		 * 2 edges on PTP_CLK. So check for truncation which happens
+		 * at periods larger than around 68.7 seconds.
+		 */
+		pin_duration = ns_to_sja1105_ticks(pin_duration / 2);
+		if (pin_duration > U32_MAX) {
+			rc = -ERANGE;
+			goto out;
+		}
+		pin_duration32 = pin_duration;
+
+		/* ptppins: 64 bit register which needs to hold a PTP time
+		 * larger than the current time, otherwise the startptpcp
+		 * command won't do anything. So advance the current time
+		 * by a number of periods in a way that won't alter the
+		 * phase offset.
+		 */
+		rc = __sja1105_ptp_gettimex(priv->ds, &now, NULL);
+		if (rc < 0)
+			goto out;
+
+		pin_start = future_base_time(pin_start, pin_duration,
+					     now + 1ull * NSEC_PER_SEC);
+		pin_start = ns_to_sja1105_ticks(pin_start);
+
+		rc = sja1105_xfer_u64(priv, SPI_WRITE, regs->ptppinst,
+				      &pin_start, NULL);
+		if (rc < 0)
+			goto out;
+
+		rc = sja1105_xfer_u32(priv, SPI_WRITE, regs->ptppindur,
+				      &pin_duration32, NULL);
+		if (rc < 0)
+			goto out;
+	}
+
+	if (on)
+		cmd.startptpcp = true;
+	else
+		cmd.stopptpcp = true;
+
+	rc = sja1105_ptp_commit(priv->ds, &cmd, SPI_WRITE);
+
+out:
+	mutex_unlock(&ptp_data->lock);
+
+	return rc;
+}
+
+static int sja1105_extts_enable(struct sja1105_private *priv,
+				struct ptp_extts_request *extts,
+				bool on)
+{
+	int rc;
+
+	/* We only support one channel */
+	if (extts->index != 0)
+		return -EOPNOTSUPP;
+
+	/* Reject requests with unsupported flags */
+	if (extts->flags)
+		return -EOPNOTSUPP;
+
+	rc = sja1105_change_ptp_clk_pin_func(priv, PTP_PF_EXTTS);
+	if (rc)
+		return rc;
+
+	if (on)
+		schedule_delayed_work(&priv->ptp_data.extts_work,
+				      SJA1105_EXTTS_INTERVAL);
+	else
+		cancel_delayed_work_sync(&priv->ptp_data.extts_work);
+
+	return 0;
+}
+
+static int sja1105_ptp_enable(struct ptp_clock_info *ptp,
+			      struct ptp_clock_request *req, int on)
+{
+	struct sja1105_ptp_data *ptp_data = ptp_caps_to_data(ptp);
+	struct sja1105_private *priv = ptp_data_to_sja1105(ptp_data);
+	int rc = -EOPNOTSUPP;
+
+	if (req->type == PTP_CLK_REQ_PEROUT)
+		rc = sja1105_per_out_enable(priv, &req->perout, on);
+	else if (req->type == PTP_CLK_REQ_EXTTS)
+		rc = sja1105_extts_enable(priv, &req->extts, on);
+
+	return rc;
+}
+
+static int sja1105_ptp_verify_pin(struct ptp_clock_info *ptp, unsigned int pin,
+				  enum ptp_pin_function func, unsigned int chan)
+{
+	struct sja1105_ptp_data *ptp_data = ptp_caps_to_data(ptp);
+	struct sja1105_private *priv = ptp_data_to_sja1105(ptp_data);
+
+	if (chan != 0 || pin != 0)
+		return -1;
+
+	switch (func) {
+	case PTP_PF_NONE:
+	case PTP_PF_PEROUT:
+		break;
+	case PTP_PF_EXTTS:
+		if (priv->info->device_id == SJA1105E_DEVICE_ID ||
+		    priv->info->device_id == SJA1105T_DEVICE_ID)
+			return -1;
+		break;
+	default:
+		return -1;
+	}
+	return 0;
+}
+
+static struct ptp_pin_desc sja1105_ptp_pin = {
+	.name = "ptp_clk",
+	.index = 0,
+	.func = PTP_PF_NONE,
+};
+
 int sja1105_ptp_clock_register(struct dsa_switch *ds)
 {
 	struct sja1105_private *priv = ds->priv;
@@ -590,8 +828,14 @@ int sja1105_ptp_clock_register(struct dsa_switch *ds)
 		.adjtime	= sja1105_ptp_adjtime,
 		.gettimex64	= sja1105_ptp_gettimex,
 		.settime64	= sja1105_ptp_settime,
+		.enable		= sja1105_ptp_enable,
+		.verify		= sja1105_ptp_verify_pin,
 		.do_aux_work	= sja1105_rxtstamp_work,
 		.max_adj	= SJA1105_MAX_ADJ_PPB,
+		.pin_config	= &sja1105_ptp_pin,
+		.n_pins		= 1,
+		.n_ext_ts	= 1,
+		.n_per_out	= 1,
 	};
 
 	skb_queue_head_init(&ptp_data->skb_rxtstamp_queue);
@@ -604,6 +848,8 @@ int sja1105_ptp_clock_register(struct dsa_switch *ds)
 	ptp_data->cmd.corrclk4ts = true;
 	ptp_data->cmd.ptpclkadd = PTP_SET_MODE;
 
+	INIT_DELAYED_WORK(&ptp_data->extts_work, sja1105_ptp_extts_work);
+
 	return sja1105_ptp_reset(ds);
 }
 
@@ -615,6 +861,7 @@ void sja1105_ptp_clock_unregister(struct dsa_switch *ds)
 	if (IS_ERR_OR_NULL(ptp_data->clock))
 		return;
 
+	cancel_delayed_work_sync(&ptp_data->extts_work);
 	ptp_cancel_worker_sync(ptp_data->clock);
 	skb_queue_purge(&ptp_data->skb_rxtstamp_queue);
 	ptp_clock_unregister(ptp_data->clock);