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

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Date:   Tue, 06 Nov 2018 19:06:25 +0530
From:   Balakrishna Godavarthi <bgodavar@...eaurora.org>
To:     Marcel Holtmann <marcel@...tmann.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 Marcel,

On 2018-11-06 18:44, Balakrishna Godavarthi wrote:
> Hi Marcel,
> 
> On 2018-11-06 18:32, Marcel Holtmann wrote:
>> 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.
> 
> [Bala]: even i feel the same. they are lot such kind of HACK's we need
> to do with current arch.
>         when can we expect btuart.c merged to bt-next. i think having
> btuart will helps us to have the control of
>         vendor porto's call's like in btusb.c
> 
>> 
>> Regards
>> 
>> Marcel

I need some clarification, do you expect some thing like this 
https://github.com/torvalds/linux/blob/master/drivers/bluetooth/btmtkuart.c 
for Qualcomm BT chip too.
it looks it is completely avoided hci_serdev.c interface.

-- 
Regards
Balakrishna.