[PATCH] Bluetooth: btusb: hci_event: handle msbc audio over USB Endpoints

[Amit K Bag <amit.k.bag@intel.com>]

For msbc encoded audio stream over usb transport, btusb driver
to be set to alternate settings 6 as per BT core spec 5.0. This
done from  hci_sync_conn_complete_evt.  The type of air mode is known
during this event.  For this reason the btusb is to be notifed
about the TRANSPARENT air mode and the ALT setting 6 is selected.
The changes are made considering some discussion over the similar
patch submitted earlier from Kuba Pawlak(link below)
https://www.spinics.net/lists/linux-bluetooth/msg64577.html

(am from https://www.spinics.net/lists/linux-bluetooth/msg76982.html)

Signed-off-by: Chethan T N <chethan.tumkur.narayan@intel.com>
Signed-off-by: Sathish Narasimman <sathish.narasimman@intel.com>
Signed-off-by: Raghuram Hegde <raghuram.hegde@intel.com>
Signed-off-by: Hsin-Yu Chao <hychao@chromium.org>
Signed-off-by: Amit K Bag <amit.k.bag@intel.com>
---
 drivers/bluetooth/btusb.c   | 145 ++++++++++++++++++++++++++++++--------------
 include/net/bluetooth/hci.h |   1 +
 net/bluetooth/hci_event.c   |   5 ++
 3 files changed, 106 insertions(+), 45 deletions(-)

diff --git a/drivers/bluetooth/btusb.c b/drivers/bluetooth/btusb.c
index a9c35ebb30f8..368cc93cb17e 100644
--- a/drivers/bluetooth/btusb.c
+++ b/drivers/bluetooth/btusb.c
@@ -57,6 +57,9 @@ static struct usb_driver btusb_driver;
 #define BTUSB_IFNUM_2		0x80000
 #define BTUSB_CW6622		0x100000
 #define BTUSB_MEDIATEK		0x200000
+#define BTUSB_ALT6_FLOW_CNTRL	6
+
+static int set_hci_packet_interval_flow = BTUSB_ALT6_FLOW_CNTRL;
 
 static const struct usb_device_id btusb_table[] = {
 	/* Generic Bluetooth USB device */
@@ -974,6 +977,38 @@ static void btusb_isoc_complete(struct urb *urb)
 	}
 }
 
+static inline void __fill_isoc_descriptor_msbc(struct urb *urb, int len,
+					       int mtu)
+{
+	int i, offset = 0;
+
+	/* For msbc ALT 6 setting the host will send the packet at continuous
+	 * flow. As per core spec 5, vol 4, part B, table 2.1. For ALT setting
+	 * 6 the HCI PACKET INTERVAL should be 7.5ms for every usb packets.
+	 * To maintain the rate we send 63bytes of usb packets alternatively for
+	 * 7ms and 8ms to maintain the rate as 7.5ms.
+	 */
+	if (set_hci_packet_interval_flow == 6)
+		set_hci_packet_interval_flow = 7;
+	else if (set_hci_packet_interval_flow == 7)
+		set_hci_packet_interval_flow = 6;
+
+	BT_DBG("len %d mtu %d", len, mtu);
+
+	for (i = 0; i < set_hci_packet_interval_flow; i++) {
+		urb->iso_frame_desc[i].offset = offset;
+		urb->iso_frame_desc[i].length = offset;
+	}
+
+	if (len && i < BTUSB_MAX_ISOC_FRAMES) {
+		urb->iso_frame_desc[i].offset = offset;
+		urb->iso_frame_desc[i].length = len;
+		i++;
+	}
+
+	urb->number_of_packets = i;
+}
+
 static inline void __fill_isoc_descriptor(struct urb *urb, int len, int mtu)
 {
 	int i, offset = 0;
@@ -1376,9 +1411,12 @@ static struct urb *alloc_isoc_urb(struct hci_dev *hdev, struct sk_buff *skb)
 
 	urb->transfer_flags  = URB_ISO_ASAP;
 
-	__fill_isoc_descriptor(urb, skb->len,
+	if (data->isoc_altsetting == 6)
+		__fill_isoc_descriptor_msbc(urb, skb->len,
+			       le16_to_cpu(data->isoc_tx_ep->wMaxPacketSize));
+	else
+		__fill_isoc_descriptor(urb, skb->len,
 			       le16_to_cpu(data->isoc_tx_ep->wMaxPacketSize));
-
 	skb->dev = (void *)hdev;
 
 	return urb;
@@ -1466,18 +1504,6 @@ static int btusb_send_frame(struct hci_dev *hdev, struct sk_buff *skb)
 	return -EILSEQ;
 }
 
-static void btusb_notify(struct hci_dev *hdev, unsigned int evt)
-{
-	struct btusb_data *data = hci_get_drvdata(hdev);
-
-	BT_DBG("%s evt %d", hdev->name, evt);
-
-	if (hci_conn_num(hdev, SCO_LINK) != data->sco_num) {
-		data->sco_num = hci_conn_num(hdev, SCO_LINK);
-		schedule_work(&data->work);
-	}
-}
-
 static inline int __set_isoc_interface(struct hci_dev *hdev, int altsetting)
 {
 	struct btusb_data *data = hci_get_drvdata(hdev);
@@ -1521,6 +1547,65 @@ static inline int __set_isoc_interface(struct hci_dev *hdev, int altsetting)
 	return 0;
 }
 
+static int bt_switch_alt_setting(struct hci_dev *hdev, int new_alts)
+{
+	struct btusb_data *data = hci_get_drvdata(hdev);
+	int err;
+
+	if (data->isoc_altsetting != new_alts) {
+		unsigned long flags;
+
+		clear_bit(BTUSB_ISOC_RUNNING, &data->flags);
+		usb_kill_anchored_urbs(&data->isoc_anchor);
+
+		/* When isochronous alternate setting needs to be
+		 * changed, because SCO connection has been added
+		 * or removed, a packet fragment may be left in the
+		 * reassembling state. This could lead to wrongly
+		 * assembled fragments.
+		 *
+		 * Clear outstanding fragment when selecting a new
+		 * alternate setting.
+		 */
+		spin_lock_irqsave(&data->rxlock, flags);
+		kfree_skb(data->sco_skb);
+		data->sco_skb = NULL;
+		spin_unlock_irqrestore(&data->rxlock, flags);
+
+		err = __set_isoc_interface(hdev, new_alts);
+		if (err < 0)
+			return err;
+	}
+	if (!test_and_set_bit(BTUSB_ISOC_RUNNING, &data->flags)) {
+		if (btusb_submit_isoc_urb(hdev, GFP_KERNEL) < 0)
+			clear_bit(BTUSB_ISOC_RUNNING, &data->flags);
+		else
+			btusb_submit_isoc_urb(hdev, GFP_KERNEL);
+	}
+
+	return 0;
+}
+
+static void btusb_notify(struct hci_dev *hdev, unsigned int evt)
+{
+	struct btusb_data *data = hci_get_drvdata(hdev);
+
+	BT_DBG("%s evt %d", hdev->name, evt);
+
+	if (hci_conn_num(hdev, SCO_LINK) != data->sco_num) {
+		data->sco_num = hci_conn_num(hdev, SCO_LINK);
+		schedule_work(&data->work);
+	}
+
+	if (evt == HCI_NOTIFY_AIR_MODE_TRANSP) {
+		/* Alt setting 6 is used for msbc encoded
+		 * audio channel
+		 */
+		if (bt_switch_alt_setting(hdev, 6) < 0)
+			BT_ERR("%s Set USB Alt6 failed", hdev->name);
+	}
+}
+
 static void btusb_work(struct work_struct *work)
 {
 	struct btusb_data *data = container_of(work, struct btusb_data, work);
@@ -1547,37 +1632,7 @@ static void btusb_work(struct work_struct *work)
 		} else {
 			new_alts = data->sco_num;
 		}
-
-		if (data->isoc_altsetting != new_alts) {
-			unsigned long flags;
-
-			clear_bit(BTUSB_ISOC_RUNNING, &data->flags);
-			usb_kill_anchored_urbs(&data->isoc_anchor);
-
-			/* When isochronous alternate setting needs to be
-			 * changed, because SCO connection has been added
-			 * or removed, a packet fragment may be left in the
-			 * reassembling state. This could lead to wrongly
-			 * assembled fragments.
-			 *
-			 * Clear outstanding fragment when selecting a new
-			 * alternate setting.
-			 */
-			spin_lock_irqsave(&data->rxlock, flags);
-			kfree_skb(data->sco_skb);
-			data->sco_skb = NULL;
-			spin_unlock_irqrestore(&data->rxlock, flags);
-
-			if (__set_isoc_interface(hdev, new_alts) < 0)
-				return;
-		}
-
-		if (!test_and_set_bit(BTUSB_ISOC_RUNNING, &data->flags)) {
-			if (btusb_submit_isoc_urb(hdev, GFP_KERNEL) < 0)
-				clear_bit(BTUSB_ISOC_RUNNING, &data->flags);
-			else
-				btusb_submit_isoc_urb(hdev, GFP_KERNEL);
-		}
+		bt_switch_alt_setting(hdev, new_alts);
 	} else {
 		clear_bit(BTUSB_ISOC_RUNNING, &data->flags);
 		usb_kill_anchored_urbs(&data->isoc_anchor);
diff --git a/include/net/bluetooth/hci.h b/include/net/bluetooth/hci.h
index 5bc1e30dedde..89ac29f1dffa 100644
--- a/include/net/bluetooth/hci.h
+++ b/include/net/bluetooth/hci.h
@@ -52,6 +52,7 @@
 #define HCI_NOTIFY_CONN_ADD		1
 #define HCI_NOTIFY_CONN_DEL		2
 #define HCI_NOTIFY_VOICE_SETTING	3
+#define HCI_NOTIFY_AIR_MODE_TRANSP	4
 
 /* HCI bus types */
 #define HCI_VIRTUAL	0
diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
index c1d3a303d97f..1c268932422c 100644
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -4231,6 +4231,11 @@ static void hci_sync_conn_complete_evt(struct hci_dev *hdev,
 		break;
 	}
 
+	if (ev->air_mode == SCO_AIRMODE_TRANSP) {
+		if (hdev->notify)
+			hdev->notify(hdev, HCI_NOTIFY_AIR_MODE_TRANSP);
+	}
+
 	hci_connect_cfm(conn, ev->status);
 	if (ev->status)
 		hci_conn_del(conn);
-- 
2.7.4