Re: [PATCH v4] Bluetooth: qca: Fix delayed hw_error handling due to missing wakeup during SSR

[Shuai Zhang <shuai.zhang@oss.qualcomm.com>]

Hi Luiz

Thanks for the suggestion.

On 3/28/2026 1:51 AM, Luiz Augusto von Dentz wrote:
> Hi Shuai,
>
> On Fri, Mar 27, 2026 at 4:33 AM Shuai Zhang
> <shuai.zhang@oss.qualcomm.com> wrote:
>> From: Shuai Zhang <quic_shuaz@quicinc.com>
>>
>> When Bluetooth controller encounters a coredump, it triggers
>> the Subsystem Restart (SSR) mechanism. The controller first
>> reports the coredump data, and once the data upload is complete,
>> it sends a hw_error event. The host relies on this event to
>> proceed with subsequent recovery actions.
>>
>> If the host has not finished processing the coredump data
>> when the hw_error event is received,
>> it sets a timer to wait until either the data processing is complete
>> or the timeout expires before handling the event.
>>
>> The current implementation lacks a wakeup trigger. As a result,
>> even if the coredump data has already been processed, the host
>> continues to wait until the timer expires, causing unnecessary
>> delays in handling the hw_error event.
>>
>> To fix this issue, adds a `wake_up_bit()` call after the host finishes
>> processing the coredump data. This ensures that the waiting thread is
>> promptly notified and can proceed to handle the hw_error event without
>> waiting for the timeout.
>>
>> Test case:
>> - Trigger controller coredump using the command: `hcitool cmd 0x3f 0c 26`.
>> - Use `btmon` to capture HCI logs.
>> - Observe the time interval between receiving the hw_error event
>> and the execution of the power-off sequence in the HCI log.
>>
>> Signed-off-by: Shuai Zhang <quic_shuaz@quicinc.com>
>> Link: https://lore.kernel.org/stable/20251107033924.3707495-2-quic_shuaz%40quicinc.com
>> Acked-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
>> ---
>> Changes v4:
>> - add Acked-by signoff
>> - Link to v3
>>    https://lore.kernel.org/all/20251107033924.3707495-1-quic_shuaz@quicinc.com/
>>
>> Changes v3:
>> - add Fixes tag
>> - Link to v2
>>    https://lore.kernel.org/all/20251106140103.1406081-1-quic_shuaz@quicinc.com/
>>
>> Changes v2:
>> - Split timeout conversion into a separate patch.
>> - Clarified commit messages and added test case description.
>> - Link to v1
>>    https://lore.kernel.org/all/20251104112601.2670019-1-quic_shuaz@quicinc.com/
>> ---
>>   drivers/bluetooth/hci_qca.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/bluetooth/hci_qca.c b/drivers/bluetooth/hci_qca.c
>> index c17a462ae..228a754a9 100644
>> --- a/drivers/bluetooth/hci_qca.c
>> +++ b/drivers/bluetooth/hci_qca.c
>> @@ -1108,7 +1108,7 @@ static void qca_controller_memdump(struct work_struct *work)
>>                                  qca->qca_memdump = NULL;
>>                                  qca->memdump_state = QCA_MEMDUMP_COLLECTED;
>>                                  cancel_delayed_work(&qca->ctrl_memdump_timeout);
>> -                               clear_bit(QCA_MEMDUMP_COLLECTION, &qca->flags);
>> +                               clear_and_wake_up_bit(QCA_MEMDUMP_COLLECTION, &qca->flags);
>>                                  clear_bit(QCA_IBS_DISABLED, &qca->flags);
>>                                  mutex_unlock(&qca->hci_memdump_lock);
>>                                  return;
>> @@ -1186,7 +1186,7 @@ static void qca_controller_memdump(struct work_struct *work)
>>                          kfree(qca->qca_memdump);
>>                          qca->qca_memdump = NULL;
>>                          qca->memdump_state = QCA_MEMDUMP_COLLECTED;
>> -                       clear_bit(QCA_MEMDUMP_COLLECTION, &qca->flags);
>> +                       clear_and_wake_up_bit(QCA_MEMDUMP_COLLECTION, &qca->flags);
>>                  }
>>
>>                  mutex_unlock(&qca->hci_memdump_lock);
>> --
>> 2.34.1
> https://sashiko.dev/#/patchset/20260327083258.1398450-1-shuai.zhang%40oss.qualcomm.com
>
> Not saying the feedback is actually valid, but if there are other part
> of the code still using clear_bit(QCA_MEMDUMP_COLLECTION then perhaps
> they should be updated as well?


Only these two locations incorrectly use clear_bit instead of 
clear_and_wake_up_bit.

  All other uses of QCA_MEMDUMP_COLLECTION only involve set_bit and 
test_bit.


Thanks,

Shuai