[PATCH net-next v7 1/2] net: ethernet: ti: am65-cpts: Enable RX HW timestamp for PTP packets using CPTS FIFO

[Chintan Vankar]

Add a new function "am65_cpts_rx_timestamp()" which checks for PTP
packets from header and timestamps them.

Add another function "am65_cpts_find_rx_ts()" which finds CPTS FIFO
Event to get the timestamp of received PTP packet.

Signed-off-by: Chintan Vankar <c-vankar@xxxxxx>
---

Link to v6:
- Due to some issue in my email client [PATCH v6 1/1] is missing from v6.

Link to v5:
https://lore.kernel.org/r/20240402114405.219100-2-c-vankar@xxxxxx/

Changes from v6 to v7:
- No changes.

Changes from v5 to v6:
- Defined lockless variant of "am65_cpts_fifo_read()" as
  "__am65_cpts_fifo_read()", suggested by Paolo to avoid acquiring the
  same lock on cpts again in "am65_cpts_fifo_read()".
- Replaced "list_del_entry()" and "list_add()" functions with equivalent
  "list_move()"  function.
- Replaced "list_del_init()" and "list_add_tail()" functions with
  equivalent "list_move_tail()" function.

 drivers/net/ethernet/ti/am65-cpts.c | 84 ++++++++++++++++++++++++++---
 drivers/net/ethernet/ti/am65-cpts.h |  6 +++
 2 files changed, 83 insertions(+), 7 deletions(-)

diff --git a/drivers/net/ethernet/ti/am65-cpts.c b/drivers/net/ethernet/ti/am65-cpts.c
index c66618d91c28..599454c1d19f 100644
--- a/drivers/net/ethernet/ti/am65-cpts.c
+++ b/drivers/net/ethernet/ti/am65-cpts.c
@@ -275,15 +275,13 @@ static bool am65_cpts_fifo_pop_event(struct am65_cpts *cpts,
 	return true;
 }
 
-static int am65_cpts_fifo_read(struct am65_cpts *cpts)
+static int __am65_cpts_fifo_read(struct am65_cpts *cpts)
 {
 	struct ptp_clock_event pevent;
 	struct am65_cpts_event *event;
 	bool schedule = false;
 	int i, type, ret = 0;
-	unsigned long flags;
 
-	spin_lock_irqsave(&cpts->lock, flags);
 	for (i = 0; i < AM65_CPTS_FIFO_DEPTH; i++) {
 		event = list_first_entry_or_null(&cpts->pool,
 						 struct am65_cpts_event, list);
@@ -312,8 +310,7 @@ static int am65_cpts_fifo_read(struct am65_cpts *cpts)
 			event->tmo = jiffies +
 				msecs_to_jiffies(AM65_CPTS_EVENT_RX_TX_TIMEOUT);
 
-			list_del_init(&event->list);
-			list_add_tail(&event->list, &cpts->events);
+			list_move_tail(&event->list, &cpts->events);
 
 			dev_dbg(cpts->dev,
 				"AM65_CPTS_EV_TX e1:%08x e2:%08x t:%lld\n",
@@ -356,14 +353,24 @@ static int am65_cpts_fifo_read(struct am65_cpts *cpts)
 	}
 
 out:
-	spin_unlock_irqrestore(&cpts->lock, flags);
-
 	if (schedule)
 		ptp_schedule_worker(cpts->ptp_clock, 0);
 
 	return ret;
 }
 
+static int am65_cpts_fifo_read(struct am65_cpts *cpts)
+{
+	unsigned long flags;
+	int ret = 0;
+
+	spin_lock_irqsave(&cpts->lock, flags);
+	ret = __am65_cpts_fifo_read(cpts);
+	spin_unlock_irqrestore(&cpts->lock, flags);
+
+	return ret;
+}
+
 static u64 am65_cpts_gettime(struct am65_cpts *cpts,
 			     struct ptp_system_timestamp *sts)
 {
@@ -906,6 +913,69 @@ static int am65_skb_get_mtype_seqid(struct sk_buff *skb, u32 *mtype_seqid)
 	return 1;
 }
 
+static u64 am65_cpts_find_rx_ts(struct am65_cpts *cpts, u32 skb_mtype_seqid)
+{
+	struct list_head *this, *next;
+	struct am65_cpts_event *event;
+	unsigned long flags;
+	u32 mtype_seqid;
+	u64 ns = 0;
+
+	spin_lock_irqsave(&cpts->lock, flags);
+	__am65_cpts_fifo_read(cpts);
+	list_for_each_safe(this, next, &cpts->events) {
+		event = list_entry(this, struct am65_cpts_event, list);
+		if (time_after(jiffies, event->tmo)) {
+			list_move(&event->list, &cpts->pool);
+			continue;
+		}
+
+		mtype_seqid = event->event1 &
+			      (AM65_CPTS_EVENT_1_MESSAGE_TYPE_MASK |
+			       AM65_CPTS_EVENT_1_SEQUENCE_ID_MASK |
+			       AM65_CPTS_EVENT_1_EVENT_TYPE_MASK);
+
+		if (mtype_seqid == skb_mtype_seqid) {
+			ns = event->timestamp;
+			list_move(&event->list, &cpts->pool);
+			break;
+		}
+	}
+	spin_unlock_irqrestore(&cpts->lock, flags);
+
+	return ns;
+}
+
+void am65_cpts_rx_timestamp(struct am65_cpts *cpts, struct sk_buff *skb)
+{
+	struct am65_cpts_skb_cb_data *skb_cb = (struct am65_cpts_skb_cb_data *)skb->cb;
+	struct skb_shared_hwtstamps *ssh;
+	int ret;
+	u64 ns;
+
+	/* am65_cpts_rx_timestamp() is called before eth_type_trans(), so
+	 * skb MAC Hdr properties are not configured yet. Hence need to
+	 * reset skb MAC header here
+	 */
+	skb_reset_mac_header(skb);
+	ret = am65_skb_get_mtype_seqid(skb, &skb_cb->skb_mtype_seqid);
+	if (!ret)
+		return; /* if not PTP class packet */
+
+	skb_cb->skb_mtype_seqid |= (AM65_CPTS_EV_RX << AM65_CPTS_EVENT_1_EVENT_TYPE_SHIFT);
+
+	dev_dbg(cpts->dev, "%s mtype seqid %08x\n", __func__, skb_cb->skb_mtype_seqid);
+
+	ns = am65_cpts_find_rx_ts(cpts, skb_cb->skb_mtype_seqid);
+	if (!ns)
+		return;
+
+	ssh = skb_hwtstamps(skb);
+	memset(ssh, 0, sizeof(*ssh));
+	ssh->hwtstamp = ns_to_ktime(ns);
+}
+EXPORT_SYMBOL_GPL(am65_cpts_rx_timestamp);
+
 /**
  * am65_cpts_tx_timestamp - save tx packet for timestamping
  * @cpts: cpts handle
diff --git a/drivers/net/ethernet/ti/am65-cpts.h b/drivers/net/ethernet/ti/am65-cpts.h
index 6e14df0be113..90296968a75c 100644
--- a/drivers/net/ethernet/ti/am65-cpts.h
+++ b/drivers/net/ethernet/ti/am65-cpts.h
@@ -22,6 +22,7 @@ void am65_cpts_release(struct am65_cpts *cpts);
 struct am65_cpts *am65_cpts_create(struct device *dev, void __iomem *regs,
 				   struct device_node *node);
 int am65_cpts_phc_index(struct am65_cpts *cpts);
+void am65_cpts_rx_timestamp(struct am65_cpts *cpts, struct sk_buff *skb);
 void am65_cpts_tx_timestamp(struct am65_cpts *cpts, struct sk_buff *skb);
 void am65_cpts_prep_tx_timestamp(struct am65_cpts *cpts, struct sk_buff *skb);
 void am65_cpts_rx_enable(struct am65_cpts *cpts, bool en);
@@ -48,6 +49,11 @@ static inline int am65_cpts_phc_index(struct am65_cpts *cpts)
 	return -1;
 }
 
+static inline void am65_cpts_rx_timestamp(struct am65_cpts *cpts,
+					  struct sk_buff *skb)
+{
+}
+
 static inline void am65_cpts_tx_timestamp(struct am65_cpts *cpts,
 					  struct sk_buff *skb)
 {
-- 
2.34.1