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Message-ID: <c5998fbd-bd63-4f7d-8f51-3dd081913449@quicinc.com>
Date: Sat, 4 May 2024 04:18:04 +0800
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Subject: Re: [PATCH v1] Bluetooth: qca: Fix BT enable failure again for
 QCA6390 after warm reboot
To: Luiz Augusto von Dentz <luiz.dentz@gmail.com>
CC: <luiz.von.dentz@intel.com>, <marcel@holtmann.org>,
        <linux-bluetooth@vger.kernel.org>, <wt@penguintechs.org>,
        <regressions@lists.linux.dev>, <stable@vger.kernel.org>
References: <1714658761-15326-1-git-send-email-quic_zijuhu@quicinc.com>
 <CABBYNZJc=Pzt02f0L3KOSLqkJ+2SwO=OZibA=0S0T3vKPDwPyw@mail.gmail.com>
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From: quic_zijuhu <quic_zijuhu@quicinc.com>
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On 5/4/2024 3:22 AM, Luiz Augusto von Dentz wrote:
> Hi Zijun,
> 
> On Thu, May 2, 2024 at 10:06 AM Zijun Hu <quic_zijuhu@quicinc.com> wrote:
>>
>> Commit 272970be3dab ("Bluetooth: hci_qca: Fix driver shutdown on closed
>> serdev") will cause below regression issue:
>>
>> BT can't be enabled after below steps:
>> cold boot -> enable BT -> disable BT -> warm reboot -> BT enable failure
>> if property enable-gpios is not configured within DT|ACPI for QCA6390.
>>
>> The commit is to fix a use-after-free issue within qca_serdev_shutdown()
>> during reboot, but also introduces this regression issue regarding above
>> steps since the VSC is not sent to reset controller during warm reboot.
>>
>> Fixed by sending the VSC to reset controller within qca_serdev_shutdown()
>> once BT was ever enabled, and the use-after-free issue is also be fixed
>> by this change since serdev is still opened when send to serdev.
>>
>> Fixes: 272970be3dab ("Bluetooth: hci_qca: Fix driver shutdown on closed serdev")
>> Cc: stable@vger.kernel.org
>> Reported-by: Wren Turkal <wt@penguintechs.org>
>> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218726
>> Signed-off-by: Zijun Hu <quic_zijuhu@quicinc.com>
>> Tested-by: Wren Turkal <wt@penguintechs.org>
>> ---
>>  drivers/bluetooth/hci_qca.c | 5 ++---
>>  1 file changed, 2 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/bluetooth/hci_qca.c b/drivers/bluetooth/hci_qca.c
>> index 0c9c9ee56592..8e35c9091486 100644
>> --- a/drivers/bluetooth/hci_qca.c
>> +++ b/drivers/bluetooth/hci_qca.c
>> @@ -2450,13 +2450,12 @@ static void qca_serdev_shutdown(struct device *dev)
>>         struct qca_serdev *qcadev = serdev_device_get_drvdata(serdev);
>>         struct hci_uart *hu = &qcadev->serdev_hu;
>>         struct hci_dev *hdev = hu->hdev;
>> -       struct qca_data *qca = hu->priv;
>>         const u8 ibs_wake_cmd[] = { 0xFD };
>>         const u8 edl_reset_soc_cmd[] = { 0x01, 0x00, 0xFC, 0x01, 0x05 };
>>
>>         if (qcadev->btsoc_type == QCA_QCA6390) {
>> -               if (test_bit(QCA_BT_OFF, &qca->flags) ||
>> -                   !test_bit(HCI_RUNNING, &hdev->flags))
> 
> This probably deserves a comment on why you end up with
> HCI_QUIRK_NON_PERSISTENT_SETUP and HCI_SETUP flags here, also why you
> are removing the flags above since that was introduce to prevent
> use-after-free this sort of revert it so I do wonder how serdev can
> still be open if you haven't tested for QCA_BT_OFF for example?
> 
okay, let me give comments at next version.
this design logic is shown below. you maybe review it.

if HCI_QUIRK_NON_PERSISTENT_SETUP is set, it means that hdev->setup()
is able to be invoked by every open() to initializate SoC without any
help. so we don't need to send the VSC to reset SoC into initial and
clean state for the next hdev->setup() call success.

otherwise, namely, HCI_QUIRK_NON_PERSISTENT_SETUP is not set.

if HCI_SETUP is set, it means hdev->setup() was never be invoked, so the
SOC is already in the initial and clean state, so we also don't need to
send the VSC to reset SOC.

otherwise, we need to send the VSC to reset Soc into a initial and clean
state for hdev->setup() call success after "warm reboot -> enable BT"

for the case commit message cares about, the only factor which decide to
send the VSC is that SoC is a initial and clean state or not after warm
reboot, any other factors are irrelevant to this decision.

why the serdev is still open after go through
(test_bit(HCI_QUIRK_NON_PERSISTENT_SETUP, &hdev->quirks)
|| hci_dev_test_flag(hdev, HCI_SETUP) checking is that
serdev is not closed by hci_uart_close().

see hci_uart_close() within drivers/bluetooth/hci_serdev.c
static int hci_uart_close(struct hci_dev *hdev)
{
......
	/* When QUIRK HCI_QUIRK_NON_PERSISTENT_SETUP is set by driver,
	 * BT SOC is completely powered OFF during BT OFF, holding port
	 * open may drain the battery.
	 */
	if (test_bit(HCI_QUIRK_NON_PERSISTENT_SETUP, &hdev->quirks)) {
		clear_bit(HCI_UART_PROTO_READY, &hu->flags);
		serdev_device_close(hu->serdev);
	}

	return 0;
}

>> +               if (test_bit(HCI_QUIRK_NON_PERSISTENT_SETUP, &hdev->quirks) ||
>> +                   hci_dev_test_flag(hdev, HCI_SETUP))
>>                         return;
>>
>>                 serdev_device_write_flush(serdev);
>> --
>> 2.7.4
>>
> 
>