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Subject: Re: Question about SC16IS752 device tree.
From:   "H. Nikolaus Schaller" <hns@goldelico.com>
In-Reply-To: <8533f999-f584-ea31-0c44-1ce29c066d88@wanyeetech.com>
Date:   Tue, 10 May 2022 17:31:13 +0200
Cc:     Paul Cercueil <paul@crapouillou.net>, jringle@gridpoint.com,
        shc_work@mail.ru, Rob Herring <robh@kernel.org>,
        Paul Boddie <paul@boddie.org.uk>,
        Jiaxun Yang <jiaxun.yang@flygoat.com>,
        linux-serial@vger.kernel.org,
        linux-mips <linux-mips@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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Message-Id: <1B523C47-1F9C-42EE-B242-EF63F89B94F9@goldelico.com>
References: <7c89db86-4055-90b5-6a67-611410f5759f@wanyeetech.com>
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 <04bd0853-7e34-5210-f1b5-f3ea8c35e484@wanyeetech.com>
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To:     Zhou Yanjie <zhouyanjie@wanyeetech.com>
Precedence: bulk

Hi,

> Am 10.05.2022 um 04:29 schrieb Zhou Yanjie =
<zhouyanjie@wanyeetech.com>:
>=20
> Hi Nikolaus,
>=20
> On 2022/5/10 =E4=B8=8A=E5=8D=884:19, H. Nikolaus Schaller wrote:
>> Hi,
>>=20
>>> Am 09.05.2022 um 20:41 schrieb Zhou Yanjie =
<zhouyanjie@wanyeetech.com>:
>>>=20
>>> Hi Paul,
>>>=20
>>> On 2022/5/10 =E4=B8=8A=E5=8D=882:13, Paul Cercueil wrote:
>>>> I can't say for sure that it's your problem, but your bluetooth =
nodes are missing "reg" properties.
>>>=20
>>> Unfortunately it doesn't seem to be the problem here, I added "reg" =
and
>>> the problem persists, and I've looked at other device trees that =
contain
>>> "brcm,bcm43438-bt", none of them use "reg", and "reg" is not =
mentioned in
>>> neither "Documentation/devicetree/bindings/serial/nxp,sc16is7xx.txt" =
nor
>>> "Documentation/devicetree/bindings/net/broadcom-bluetooth.yaml".
>> what happens if you remove the serdev children from DTS? Does the =
driver create two separate /dev/tty ports? And do they work?
>=20
>=20
> Yes, there will be two separate /dev/tty ports (ttySC0 and ttySC1), =
and
> both ports can work normally, but at this time the two bluetooth =
modules
> are not working.
>=20
> I guess it is because the driver does not detect bluetooth module =
nodes,
> so the inability to operate "reset-gpios" and "device-wakeup-gpios" =
causes
> the bluetooth module to work incorrectly.

I would assume that it is not prepared to handle two serdev subnodes and
assign the right gpios.

>=20
>=20
>>=20
>> Maybe the sc16is752 driver does not separate them for child nodes, =
i.e. while "reg" should be added it may not be handled?
>=20
>=20
> I'm not too sure, I'm not very familiar with serial port systems.
> If the truth is what you think, how should I improve it?

Unfortunately I also don't know how the serdev implementation really =
works.

It was my nagging to make it happen by persistently proposing a =
non-universal
solutionsome years ago until one of the maintainers had mercy to write a =
general
solution. So I could switch my driver to simply use the serdev API. It =
was for a GPS
client device but not a tty side driver.

I think if you look up the first patches for the serdev interface this =
should
reveal the original author an he should be able to help.

BR,
Nikolaus