2018-06-06 06:22:48

by Amit K Bag

Subject: [PATCH] Bluetooth: btusb: Avoid race condition during controller recovery

From: Chethan T N <[email protected]>

Observed race condition during controller recovery mechanism
resulting the controller not responding to the reset command.

To avoid such race condition need a delay of 2ms soon after the
USB re-enumeration and before sending the Reset command which shall
allow controller to completely recover and process the Reset command.

BUG=b:64035404
TEST=Magic tethering, P0 and P1 santiy test cases, kernel-boot log

Signed-off-by: Chethan T N <[email protected]>
Signed-off-by: Amit K Bag <[email protected]>
---
drivers/bluetooth/btusb.c | 9 +++++++++
1 file changed, 9 insertions(+)

diff --git a/drivers/bluetooth/btusb.c b/drivers/bluetooth/btusb.c
index f73a27ea28cc..2303ac037240 100644
--- a/drivers/bluetooth/btusb.c
+++ b/drivers/bluetooth/btusb.c
@@ -1743,6 +1743,15 @@ static int btusb_setup_intel(struct hci_dev *hdev)

BT_DBG("%s", hdev->name);

+ /* Observed race condition during controller recovery mechanism
+ * resulting the controller not responding to the reset command.
+ *
+ * To avoid such race condition need a delay of 2ms soon after the
+ * USB re-enumeration and before sending the Reset command which shall
+ * allow controller to completely recover and process the Reset command.
+ */
+ mdelay(5);
+
/* The controller has a bug with the first HCI command sent to it
* returning number of completed commands as zero. This would stall the
* command processing in the Bluetooth core.
--
2.7.4

2018-06-06 06:23:00

by Amit K Bag

Subject: RE: [PATCH] Bluetooth: btusb: Avoid race condition during controller recovery

Hello Marcel,

> Observed race condition during controller recovery mechanism resulting the controller not responding to the reset command.
>
> To avoid such race condition need a delay of 2ms soon after the USB re-enumeration and before sending the Reset command which shall allow controller to completely recover and process the Reset command.
>
> BUG=b:64035404
> TEST=Magic tethering, P0 and P1 santiy test cases, kernel-boot log
>
> Signed-off-by: Chethan T N <[email protected]>
> Signed-off-by: Amit K Bag <[email protected]>
> ---
> drivers/bluetooth/btusb.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/drivers/bluetooth/btusb.c b/drivers/bluetooth/btusb.c index f73a27ea28cc..c7fce9c11889 100644
> --- a/drivers/bluetooth/btusb.c
> +++ b/drivers/bluetooth/btusb.c
> @@ -1743,6 +1743,15 @@ static int btusb_setup_intel(struct hci_dev *hdev)
>
> BT_DBG("%s", hdev->name);
>
> + /* Observed race condition during controller recovery mechanism
> + * resulting the controller not responding to the reset command.
> + *
> + * To avoid such race condition need a delay of 2ms soon after the
> + * USB re-enumeration and before sending the Reset command which shall
> + * allow controller to completely recover and process the Reset command.
> + */
> + mdelay(2);
> +

I will provide a new patch. Please ignore this patch.

Thanks & Regards,
Amit Bag