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

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Date:   Tue, 13 Nov 2018 18:14:04 -0800
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Balakrishna Godavarthi <bgodavar@...eaurora.org>
Cc:     Marcel Holtmann <marcel@...tmann.org>,
        Johan Hedberg <johan.hedberg@...il.com>,
        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

On Tue, Nov 06, 2018 at 06:44:07PM +0530, 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);

This patch doesn't apply cleanly against bluetooth-next, looks like
you have the unrelated "Bluetooth: hci_qca: Set
HCI_QUIRK_USE_BDADDR_PROPERTY for wcn3990"
(https://lore.kernel.org/patchwork/patch/1004372/) in your tree.

> > > > > 		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

btuart was initially part of the 'add support for Bluetooth on MT7622
SoC' series (https://lore.kernel.org/patchwork/patch/960806/), but was
dropped with v6
(https://lore.kernel.org/patchwork/project/lkml/list/?series=360046)
upon Marcel's request: 'Frankly I prefer to keep the btuart.c driver
for drivers that really just use H:4 as transport protocol. If the
protocol is only H:4 alike and has extra headers, then it should be a
separate driver.' (https://lore.kernel.org/patchwork/patch/960806/#1148426).

Cheers

Matthias