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

[Shuai Zhang]

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@xxxxxxxxxxxxxxxx> wrote:
> > From: Shuai Zhang <quic_shuaz@xxxxxxxxxxx>
> >
> > 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@xxxxxxxxxxx>
> > Link: https://lore.kernel.org/stable/20251107033924.3707495-2-quic_shuaz%40quicinc.com
> > Acked-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>
> > ---
> > Changes v4:
> > - add Acked-by signoff
> > - Link to v3
> >    https://lore.kernel.org/all/20251107033924.3707495-1-quic_shuaz@xxxxxxxxxxx/
> >
> > Changes v3:
> > - add Fixes tag
> > - Link to v2
> >    https://lore.kernel.org/all/20251106140103.1406081-1-quic_shuaz@xxxxxxxxxxx/
> >
> > 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@xxxxxxxxxxx/
> > ---
> >   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