Bluetooth: Enter active mode before establishing a SCO link.

When in sniff mode with a long interval time (1.28s) it can take 4+ seconds
to establish a SCO link. Fix by requesting active mode before requesting
SCO connection. This improves SCO setup time to ~500ms.

Bluetooth headsets that use a long interval time, and exhibit the long
SCO connection time include Motorola H790, HX1 and H17. They have a
CSR 2.1 chipset.

Verified this behavior and fix with host Bluetooth chipsets: BCM4329 and
TI1271.

2009-10-13 14:17:46.183722 > HCI Event: Mode Change (0x14) plen 6
    status 0x00 handle 1 mode 0x02 interval 2048
    Mode: Sniff
2009-10-13 14:17:53.436285 < HCI Command: Setup Synchronous Connection (0x01|0x0028) plen 17
    handle 1 voice setting 0x0060
2009-10-13 14:17:53.445593 > HCI Event: Command Status (0x0f) plen 4
    Setup Synchronous Connection (0x01|0x0028) status 0x00 ncmd 1
2009-10-13 14:17:57.788855 > HCI Event: Synchronous Connect Complete 0x2c) plen 17
    status 0x00 handle 257 bdaddr 00:1A:0E:F1:A4:7F type eSCO
    Air mode: CVSD
Signed-off-by: NNick Pelly <npelly@google.com>
Signed-off-by: NMarcel Holtmann <marcel@holtmann.org>

net/bluetooth/hci_conn.c

@@ -377,6 +377,9 @@ struct hci_conn *hci_connect(struct hci_dev *hdev, int type, bdaddr_t *dst, __u8
 
 	if (acl->state == BT_CONNECTED &&
 			(sco->state == BT_OPEN || sco->state == BT_CLOSED)) {
+		acl->power_save = 1;
+		hci_conn_enter_active_mode(acl);
+
 		if (lmp_esco_capable(hdev))
 			hci_setup_sync(sco, acl->handle);
 		else