Bluetooth: btusb: check conditions before enabling USB ALT 3 for WBS

Signed-off-by: Mike Pagano <mpagano@gentoo.org>

2 files changed, 88 insertions, 0 deletions

diff --git a/0000_README b/0000_README
index 2619131d..99766a30 100644
--- a/0000_README
+++ b/0000_README
@@ -55,6 +55,10 @@ Patch:  2000_BT-Check-key-sizes-only-if-Secure-Simple-Pairing-enabled.patch
 From:   https://lore.kernel.org/linux-bluetooth/20190522070540.48895-1-marcel@holtmann.org/raw
 Desc:   Bluetooth: Check key sizes only when Secure Simple Pairing is enabled. See bug #686758
 
+Patch:  2700_Bluetooth-usb-alt-3-for-WBS.patch
+From:   https://git.kernel.org/pub/scm/linux/kernel/git/bluetooth/bluetooth-next.git/commit/?id=55981d3541812234e687062926ff199c83f79a39
+Desc:   Bluetooth: btusb: check conditions before enabling USB ALT 3 for WBS
+
 Patch:  2900_tmp513-Fix-build-issue-by-selecting-CONFIG_REG.patch
 From:   https://bugs.gentoo.org/710790
 Desc:   tmp513 requies REGMAP_I2C to build.  Select it by default in Kconfig. See bug #710790. Thanks to Phil Stracchino
diff --git a/2700_Bluetooth-usb-alt-3-for-WBS.patch b/2700_Bluetooth-usb-alt-3-for-WBS.patch
new file mode 100644
index 00000000..e0a67ea2
--- /dev/null
+++ b/2700_Bluetooth-usb-alt-3-for-WBS.patch
@@ -0,0 +1,84 @@
+From 55981d3541812234e687062926ff199c83f79a39 Mon Sep 17 00:00:00 2001
+From: Pauli Virtanen <pav@iki.fi>
+Date: Mon, 26 Jul 2021 21:02:06 +0300
+Subject: Bluetooth: btusb: check conditions before enabling USB ALT 3 for WBS
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+Some USB BT adapters don't satisfy the MTU requirement mentioned in
+commit e848dbd364ac ("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: Pauli Virtanen <pav@iki.fi>
+Fixes: e848dbd364ac ("Bluetooth: btusb: Add support USB ALT 3 for WBS")
+Tested-by: Michał Kępień <kernel@kempniu.pl>
+Tested-by: Jonathan Lampérth <jon@h4n.dev>
+Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
+---
+ drivers/bluetooth/btusb.c | 22 ++++++++++++++--------
+ 1 file changed, 14 insertions(+), 8 deletions(-)
+
+diff --git a/drivers/bluetooth/btusb.c b/drivers/bluetooth/btusb.c
+index 488f110e17e27..2336f731dbc7e 100644
+--- a/drivers/bluetooth/btusb.c
++++ b/drivers/bluetooth/btusb.c
+@@ -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)
+-- 
+cgit 1.2.3-1.el7
+