Bluetooth: hci_core: Enable buffer flow control for SCO/eSCO

This enables buffer flow control for SCO/eSCO
(see: Bluetooth Core 6.0 spec: 6.22. Synchronous Flow Control Enable),
recently this has caused the following problem and is actually a nice
addition for the likes of Socket TX complete:

< HCI Command: Read Buffer Size (0x04|0x0005) plen 0
> HCI Event: Command Complete (0x0e) plen 11
      Read Buffer Size (0x04|0x0005) ncmd 1
        Status: Success (0x00)
        ACL MTU: 1021 ACL max packet: 5
        SCO MTU: 240  SCO max packet: 8
...
< SCO Data TX: Handle 257 flags 0x00 dlen 120
< SCO Data TX: Handle 257 flags 0x00 dlen 120
< SCO Data TX: Handle 257 flags 0x00 dlen 120
< SCO Data TX: Handle 257 flags 0x00 dlen 120
< SCO Data TX: Handle 257 flags 0x00 dlen 120
< SCO Data TX: Handle 257 flags 0x00 dlen 120
< SCO Data TX: Handle 257 flags 0x00 dlen 120
< SCO Data TX: Handle 257 flags 0x00 dlen 120
< SCO Data TX: Handle 257 flags 0x00 dlen 120
> HCI Event: Hardware Error (0x10) plen 1
        Code: 0x0a

To fix the code will now attempt to enable buffer flow control when
HCI_QUIRK_SYNC_FLOWCTL_SUPPORTED is set by the driver:

< HCI Command: Write Sync Fl.. (0x03|0x002f) plen 1
        Flow control: Enabled (0x01)
> HCI Event: Command Complete (0x0e) plen 4
      Write Sync Flow Control Enable (0x03|0x002f) ncmd 1
        Status: Success (0x00)

On success then HCI_SCO_FLOWCTL would be set which indicates sco_cnt
shall be used for flow contro.

Fixes: 7fedd3bb6b77 ("Bluetooth: Prioritize SCO traffic")
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Tested-by: Pauli Virtanen <pav@iki.fi>

3 files changed, 54 insertions, 34 deletions

diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
index 012fc107901a..94d9147612da 100644
--- a/net/bluetooth/hci_core.c
+++ b/net/bluetooth/hci_core.c
@@ -3552,42 +3552,27 @@ static void __check_timeout(struct hci_dev *hdev, unsigned int cnt, u8 type)
 }
 
 /* Schedule SCO */
-static void hci_sched_sco(struct hci_dev *hdev)
+static void hci_sched_sco(struct hci_dev *hdev, __u8 type)
 {
 	struct hci_conn *conn;
 	struct sk_buff *skb;
-	int quote;
+	int quote, *cnt;
+	unsigned int pkts = hdev->sco_pkts;
 
-	BT_DBG("%s", hdev->name);
+	bt_dev_dbg(hdev, "type %u", type);
 
-	if (!hci_conn_num(hdev, SCO_LINK))
+	if (!hci_conn_num(hdev, type) || !pkts)
 		return;
 
-	while (hdev->sco_cnt && (conn = hci_low_sent(hdev, SCO_LINK, &quote))) {
-		while (quote-- && (skb = skb_dequeue(&conn->data_q))) {
-			BT_DBG("skb %p len %d", skb, skb->len);
-			hci_send_frame(hdev, skb);
-
-			conn->sent++;
-			if (conn->sent == ~0)
-				conn->sent = 0;
-		}
-	}
-}
-
-static void hci_sched_esco(struct hci_dev *hdev)
-{
-	struct hci_conn *conn;
-	struct sk_buff *skb;
-	int quote;
-
-	BT_DBG("%s", hdev->name);
-
-	if (!hci_conn_num(hdev, ESCO_LINK))
-		return;
+	/* Use sco_pkts if flow control has not been enabled which will limit
+	 * the amount of buffer sent in a row.
+	 */
+	if (!hci_dev_test_flag(hdev, HCI_SCO_FLOWCTL))
+		cnt = &pkts;
+	else
+		cnt = &hdev->sco_cnt;
 
-	while (hdev->sco_cnt && (conn = hci_low_sent(hdev, ESCO_LINK,
-						     &quote))) {
+	while (*cnt && (conn = hci_low_sent(hdev, type, &quote))) {
 		while (quote-- && (skb = skb_dequeue(&conn->data_q))) {
 			BT_DBG("skb %p len %d", skb, skb->len);
 			hci_send_frame(hdev, skb);
@@ -3595,8 +3580,17 @@ static void hci_sched_esco(struct hci_dev *hdev)
 			conn->sent++;
 			if (conn->sent == ~0)
 				conn->sent = 0;
+			(*cnt)--;
 		}
 	}
+
+	/* Rescheduled if all packets were sent and flow control is not enabled
+	 * as there could be more packets queued that could not be sent and
+	 * since no HCI_EV_NUM_COMP_PKTS event will be generated the reschedule
+	 * needs to be forced.
+	 */
+	if (!pkts && !hci_dev_test_flag(hdev, HCI_SCO_FLOWCTL))
+		queue_work(hdev->workqueue, &hdev->tx_work);
 }
 
 static void hci_sched_acl_pkt(struct hci_dev *hdev)
@@ -3632,8 +3626,8 @@ static void hci_sched_acl_pkt(struct hci_dev *hdev)
 			chan->conn->sent++;
 
 			/* Send pending SCO packets right away */
-			hci_sched_sco(hdev);
-			hci_sched_esco(hdev);
+			hci_sched_sco(hdev, SCO_LINK);
+			hci_sched_sco(hdev, ESCO_LINK);
 		}
 	}
 
@@ -3688,8 +3682,8 @@ static void hci_sched_le(struct hci_dev *hdev)
 			chan->conn->sent++;
 
 			/* Send pending SCO packets right away */
-			hci_sched_sco(hdev);
-			hci_sched_esco(hdev);
+			hci_sched_sco(hdev, SCO_LINK);
+			hci_sched_sco(hdev, ESCO_LINK);
 		}
 	}
 
@@ -3734,8 +3728,8 @@ static void hci_tx_work(struct work_struct *work)
 
 	if (!hci_dev_test_flag(hdev, HCI_USER_CHANNEL)) {
 		/* Schedule queues and send stuff to HCI driver */
-		hci_sched_sco(hdev);
-		hci_sched_esco(hdev);
+		hci_sched_sco(hdev, SCO_LINK);
+		hci_sched_sco(hdev, ESCO_LINK);
 		hci_sched_iso(hdev);
 		hci_sched_acl(hdev);
 		hci_sched_le(hdev);
diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
index 19e19c9f5e68..6d0138b778aa 100644
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -4445,9 +4445,11 @@ static void hci_num_comp_pkts_evt(struct hci_dev *hdev, void *data,
 			break;
 
 		case SCO_LINK:
+		case ESCO_LINK:
 			hdev->sco_cnt += count;
 			if (hdev->sco_cnt > hdev->sco_pkts)
 				hdev->sco_cnt = hdev->sco_pkts;
+
 			break;
 
 		case ISO_LINK:
diff --git a/net/bluetooth/hci_sync.c b/net/bluetooth/hci_sync.c
index c4c2cf51b219..609b035e5c90 100644
--- a/net/bluetooth/hci_sync.c
+++ b/net/bluetooth/hci_sync.c
@@ -3769,6 +3769,28 @@ static int hci_write_ca_timeout_sync(struct hci_dev *hdev)
 				     sizeof(param), &param, HCI_CMD_TIMEOUT);
 }
 
+/* Enable SCO flow control if supported */
+static int hci_write_sync_flowctl_sync(struct hci_dev *hdev)
+{
+	struct hci_cp_write_sync_flowctl cp;
+	int err;
+
+	/* Check if the controller supports SCO and HCI_OP_WRITE_SYNC_FLOWCTL */
+	if (!lmp_sco_capable(hdev) || !(hdev->commands[10] & BIT(4)) ||
+	    !test_bit(HCI_QUIRK_SYNC_FLOWCTL_SUPPORTED, &hdev->quirks))
+		return 0;
+
+	memset(&cp, 0, sizeof(cp));
+	cp.enable = 0x01;
+
+	err = __hci_cmd_sync_status(hdev, HCI_OP_WRITE_SYNC_FLOWCTL,
+				    sizeof(cp), &cp, HCI_CMD_TIMEOUT);
+	if (!err)
+		hci_dev_set_flag(hdev, HCI_SCO_FLOWCTL);
+
+	return err;
+}
+
 /* BR Controller init stage 2 command sequence */
 static const struct hci_init_stage br_init2[] = {
 	/* HCI_OP_READ_BUFFER_SIZE */
@@ -3787,6 +3809,8 @@ static const struct hci_init_stage br_init2[] = {
 	HCI_INIT(hci_clear_event_filter_sync),
 	/* HCI_OP_WRITE_CA_TIMEOUT */
 	HCI_INIT(hci_write_ca_timeout_sync),
+	/* HCI_OP_WRITE_SYNC_FLOWCTL */
+	HCI_INIT(hci_write_sync_flowctl_sync),
 	{}
 };