Bluetooth: ISO: Support SCM_TIMESTAMPING for ISO TS

User-space applications (e.g. PipeWire) depend on
ISO-formatted timestamps for precise audio sync.

The ISO ts is based on the controller’s clock domain,
so hardware timestamping (hwtimestamp) must be used.

Ref: Documentation/networking/timestamping.rst,
section 3.1 Hardware Timestamping.

Signed-off-by: Yang Li <yang.li@amlogic.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

Author: Yang Li

net/bluetooth/iso.c

@@ -2289,6 +2289,7 @@ static void iso_disconn_cfm(struct hci_conn *hcon, __u8 reason)
 void iso_recv(struct hci_conn *hcon, struct sk_buff *skb, u16 flags)
 {
 	struct iso_conn *conn = hcon->iso_data;
+	struct skb_shared_hwtstamps *hwts;
 	__u16 pb, ts, len, sn;
 
 	if (!conn)
@@ -2312,13 +2313,16 @@ void iso_recv(struct hci_conn *hcon, struct sk_buff *skb, u16 flags)
 		if (ts) {
 			struct hci_iso_ts_data_hdr *hdr;
 
-			/* TODO: add timestamp to the packet? */
 			hdr = skb_pull_data(skb, HCI_ISO_TS_DATA_HDR_SIZE);
 			if (!hdr) {
 				BT_ERR("Frame is too short (len %d)", skb->len);
 				goto drop;
 			}
 
+			/*  Record the timestamp to skb*/
+			hwts = skb_hwtstamps(skb);
+			hwts->hwtstamp = us_to_ktime(le32_to_cpu(hdr->ts));
+
 			sn = __le16_to_cpu(hdr->sn);
 			len = __le16_to_cpu(hdr->slen);
 		} else {