Commit 55981d35 authored by Pauli Virtanen's avatar Pauli Virtanen Committed by Luiz Augusto von Dentz
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Bluetooth: btusb: check conditions before enabling USB ALT 3 for WBS

Some USB BT adapters don't satisfy the MTU requirement mentioned in
commit e848dbd3

 ("Bluetooth: btusb: Add support USB ALT 3 for WBS")
and have ALT 3 setting that produces no/garbled audio. Some adapters
with larger MTU were also reported to have problems with ALT 3.

Add a flag and check it and MTU before selecting ALT 3, falling back to
ALT 1. Enable the flag for Realtek, restoring the previous behavior for
non-Realtek devices.

Tested with USB adapters (mtu<72, no/garbled sound with ALT3, ALT1
works) BCM20702A1 0b05:17cb, CSR8510A10 0a12:0001, and (mtu>=72, ALT3
works) RTL8761BU 0bda:8771, Intel AX200 8087:0029 (after disabling
ALT6). Also got reports for (mtu>=72, ALT 3 reported to produce bad
audio) Intel 8087:0a2b.
Signed-off-by: default avatarPauli Virtanen <pav@iki.fi>
Fixes: e848dbd3

 ("Bluetooth: btusb: Add support USB ALT 3 for WBS")
Tested-by: default avatarMichał Kępień <kernel@kempniu.pl>
Tested-by: default avatarJonathan Lampérth <jon@h4n.dev>
Signed-off-by: default avatarLuiz Augusto von Dentz <luiz.von.dentz@intel.com>
parent e1dee2c1
......@@ -528,6 +528,7 @@ static const struct dmi_system_id btusb_needs_reset_resume_table[] = {
#define BTUSB_HW_RESET_ACTIVE 12
#define BTUSB_TX_WAIT_VND_EVT 13
#define BTUSB_WAKEUP_DISABLE 14
#define BTUSB_USE_ALT3_FOR_WBS 15
struct btusb_data {
struct hci_dev *hdev;
......@@ -1761,16 +1762,20 @@ static void btusb_work(struct work_struct *work)
/* Bluetooth USB spec recommends alt 6 (63 bytes), but
* many adapters do not support it. Alt 1 appears to
* work for all adapters that do not have alt 6, and
* which work with WBS at all.
* which work with WBS at all. Some devices prefer
* alt 3 (HCI payload >= 60 Bytes let air packet
* data satisfy 60 bytes), requiring
* MTU >= 3 (packets) * 25 (size) - 3 (headers) = 72
* see also Core spec 5, vol 4, B 2.1.1 & Table 2.1.
*/
new_alts = btusb_find_altsetting(data, 6) ? 6 : 1;
/* Because mSBC frames do not need to be aligned to the
* SCO packet boundary. If support the Alt 3, use the
* Alt 3 for HCI payload >= 60 Bytes let air packet
* data satisfy 60 bytes.
*/
if (new_alts == 1 && btusb_find_altsetting(data, 3))
if (btusb_find_altsetting(data, 6))
new_alts = 6;
else if (btusb_find_altsetting(data, 3) &&
hdev->sco_mtu >= 72 &&
test_bit(BTUSB_USE_ALT3_FOR_WBS, &data->flags))
new_alts = 3;
else
new_alts = 1;
}
if (btusb_switch_alt_setting(hdev, new_alts) < 0)
......@@ -3882,6 +3887,7 @@ static int btusb_probe(struct usb_interface *intf,
* (DEVICE_REMOTE_WAKEUP)
*/
set_bit(BTUSB_WAKEUP_DISABLE, &data->flags);
set_bit(BTUSB_USE_ALT3_FOR_WBS, &data->flags);
}
if (!reset)
......
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