Bluetooth: hci_event: Fix setting of unicast qos interval

qos->ucast interval reffers to the SDU interval, and should not
be set to the interval value reported by the LE CIS Established
event since the latter reffers to the ISO interval. These two
interval are not the same thing:

BLUETOOTH CORE SPECIFICATION Version 5.3 | Vol 6, Part G

Isochronous interval:
The time between two consecutive BIS or CIS events (designated
ISO_Interval in the Link Layer)

SDU interval:
The nominal time between two consecutive SDUs that are sent or
received by the upper layer.

So this instead uses the following formula from the spec to calculate
the resulting SDU interface:

BLUETOOTH CORE SPECIFICATION Version 5.4 | Vol 6, Part G
page 3075:

Transport_Latency_C_To_P = CIG_Sync_Delay + (FT_C_To_P) ×
ISO_Interval + SDU_Interval_C_To_P
Transport_Latency_P_To_C = CIG_Sync_Delay + (FT_P_To_C) ×
ISO_Interval + SDU_Interval_P_To_C

Link: bluez/bluez#823
Fixes: 2be22f1 ("Bluetooth: hci_event: Fix parsing of CIS Established Event")
Signed-off-by: Luiz Augusto von Dentz <[email protected]>

net/bluetooth/hci_event.c

@@ -6667,6 +6667,7 @@ static void hci_le_cis_estabilished_evt(struct hci_dev *hdev, void *data,
 	struct bt_iso_qos *qos;
 	bool pending = false;
 	u16 handle = __le16_to_cpu(ev->handle);
+	u32 c_sdu_interval, p_sdu_interval;
 
 	bt_dev_dbg(hdev, "status 0x%2.2x", ev->status);
 
@@ -6691,12 +6692,25 @@ static void hci_le_cis_estabilished_evt(struct hci_dev *hdev, void *data,
 
 	pending = test_and_clear_bit(HCI_CONN_CREATE_CIS, &conn->flags);
 
-	/* Convert ISO Interval (1.25 ms slots) to SDU Interval (us) */
-	qos->ucast.in.interval = le16_to_cpu(ev->interval) * 1250;
-	qos->ucast.out.interval = qos->ucast.in.interval;
+	/* BLUETOOTH CORE SPECIFICATION Version 5.4 | Vol 6, Part G
+	 * page 3075:
+	 * Transport_Latency_C_To_P = CIG_Sync_Delay + (FT_C_To_P) ×
+	 * ISO_Interval + SDU_Interval_C_To_P
+	 * ...
+	 * SDU_Interval = (CIG_Sync_Delay + (FT) x ISO_Interval) -
+	 *					Transport_Latency
+	 */
+	c_sdu_interval = (get_unaligned_le24(ev->cig_sync_delay) +
+			 (ev->c_ft * le16_to_cpu(ev->interval) * 1250)) -
+			get_unaligned_le24(ev->c_latency);
+	p_sdu_interval = (get_unaligned_le24(ev->cig_sync_delay) +
+			 (ev->p_ft * le16_to_cpu(ev->interval) * 1250)) -
+			get_unaligned_le24(ev->p_latency);
 
 	switch (conn->role) {
 	case HCI_ROLE_SLAVE:
+		qos->ucast.in.interval = c_sdu_interval;
+		qos->ucast.out.interval = p_sdu_interval;
 		/* Convert Transport Latency (us) to Latency (msec) */
 		qos->ucast.in.latency =
 			DIV_ROUND_CLOSEST(get_unaligned_le24(ev->c_latency),
@@ -6710,6 +6724,8 @@ static void hci_le_cis_estabilished_evt(struct hci_dev *hdev, void *data,
 		qos->ucast.out.phy = ev->p_phy;
 		break;
 	case HCI_ROLE_MASTER:
+		qos->ucast.in.interval = p_sdu_interval;
+		qos->ucast.out.interval = c_sdu_interval;
 		/* Convert Transport Latency (us) to Latency (msec) */
 		qos->ucast.out.latency =
 			DIV_ROUND_CLOSEST(get_unaligned_le24(ev->c_latency),