linux-kernel - Re: [PATCH v1 3/4] Bluetooth: hci_qca: clear HCI_QUIRK_RESET_ON

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Date:   Tue, 6 Nov 2018 14:02:03 +0100
From:   Marcel Holtmann <marcel@...tmann.org>
To:     Balakrishna Godavarthi <bgodavar@...eaurora.org>
Cc:     Johan Hedberg <johan.hedberg@...il.com>,
        Matthias Kaehlcke <mka@...omium.org>,
        open list <linux-kernel@...r.kernel.org>,
        linux-bluetooth@...r.kernel.org, hemantg@...eaurora.org,
        linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v1 3/4] Bluetooth: hci_qca: clear HCI_QUIRK_RESET_ON_CLOSE
 flag

Hi Balakrishna,

>>> During hci down we are sending reset command to chip, which
>>> is not required for wcn3990, as hdev->shutdown() will turn off the
>>> regulators.
>>> Signed-off-by: Balakrishna Godavarthi <bgodavar@...eaurora.org>
>>> ---
>>> drivers/bluetooth/hci_qca.c | 1 +
>>> 1 file changed, 1 insertion(+)
>>> diff --git a/drivers/bluetooth/hci_qca.c b/drivers/bluetooth/hci_qca.c
>>> index 8301663f0004..97b57e0f4725 100644
>>> --- a/drivers/bluetooth/hci_qca.c
>>> +++ b/drivers/bluetooth/hci_qca.c
>>> @@ -1190,6 +1190,7 @@ static int qca_setup(struct hci_uart *hu)
>>> 		 */
>>> 		set_bit(HCI_QUIRK_NON_PERSISTENT_SETUP, &hdev->quirks);
>>> 		set_bit(HCI_QUIRK_USE_BDADDR_PROPERTY, &hdev->quirks);
>>> +		clear_bit(HCI_QUIRK_RESET_ON_CLOSE, &hdev->quirks);
>>> 		hu->hdev->shutdown = qca_power_off;
>>> 		ret = qca_wcn3990_init(hu);
>>> 		if (ret)
>> I am pretty certain that you didn’t want this quirk:
>>        /* When this quirk is set, the HCI Reset command is send when
>>         * closing the transport instead of when opening it.
>> This quirk is for Bluetooth 1.0b devices where the HCI_Reset behavior
>> was not clear or for devices that actually misbehave with the initial
>> HCI_Reset.
>> In addition, you commit message is totally misleading. That is not
>> what is happening with this quirk.
>> Regards
>> Marcel
> 
> My intention was reset command is not required when we do an hci down.
> this is because of hdev->shutdown will turn off the regulators.
> It is like turning off the chip. sending reset command after turning off the chip is not required.
> 
> I understand the usage of the quirk, will update the commit text.

you are papering over the issue. Actually hci_serdev.c:hci_uart_register_device() is the culprit with the legacy code copied over from hci_ldisc.c:hci_uart_register_dev(). I think there is no point doing all this legacy line discipline quirk handling until it is really needed. The serdev drivers are all for recent hardware.

That said, having moved over to a btuart.c approach and killed the whole hci_serdev.c thing would have been a lot better here. You will keep running in weird situations where 18 year old code keeps surprising you.

Regards

Marcel