linux-kernel - Re: [PATCH v6 0/2] usb: serial: add support for CH348

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Date: Wed, 3 Apr 2024 15:27:25 +0200
From: David Heidelberg <david@...t.cz>
To: Corentin LABBE <clabbe@...libre.com>,
 Nicolas Frattaroli <frattaroli.nicolas@...il.com>
Cc: gregkh@...uxfoundation.org, johan@...nel.org,
 linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: [PATCH v6 0/2] usb: serial: add support for CH348

Hello Corentin,

is there chance you find some time to upstream this?
In the worst case I would try to find some time to look into this, so it 
would have chance to get merged.

Thanks
David

On 20/11/2023 13:29, Corentin LABBE wrote:
> Le Wed, Aug 30, 2023 at 07:43:03PM +0200, Nicolas Frattaroli a écrit :
>> On Mittwoch, 28. Juni 2023 15:38:32 CEST Corentin Labbe wrote:
>>> Hello
>>>
>>> The CH348 is an octo serial to USB adapter.
>>> The following patch adds a driver for supporting it.
>>> Since there is no public datasheet, unfortunatly it remains some magic values.
>>>
>>> It was tested with a large range of baud from 1200 to 1500000 and used with
>>> success in one of our kernel CI testlab.
>>>
>>> Regards
>>>
>>> [...]
>> Hello,
>>
>> thank you for your work on this. I recently made myself a CH348
>> board and used this patchset with a small test application[1]
>> to see how it performs. Specifically, I ran this on an RK3566
>> single board computer, connecting one serial adapter to the
>> other, with the test as follows:
>>
>>   ./serialtest /dev/ttyUSB0 9600 # UART0 of 1st CH348 board
>>   ./serialtest /dev/ttyUSB8 9600 # UART0 of 2nd CH348 board
>>
>> One problem I've noticed is that writes to the tty fd never
>> seem to block. On two CH340 adapters I have, they do seem to
>> block, whereas here, you can see from the statistics at the
>> end that magnitudes more bytes were written than read, with
>> seemingly most of them being discarded. From my reading of
>> the termios parameters I set, this shouldn't be the case,
>> right?
>>
>> You can see from the error percentage that it gets less
>> bad as you increase the serial baudrate; I've tested up
>> to 6 mbaud like this. I assume that's because less written
>> bytes get discarded.
>>
>> Any ideas on whether I'm relying on weird driver behaviour
>> with the blocking here or if this driver actually has a
>> defect whereby it never signals to userspace that less
>> bytes were written than have been submitted?
>>
>> Kind regards,
>> Nicolas Frattaroli
>>
>> [1]: https://github.com/CounterPillow/serialtest
>>
> Hello
>
> Sorry for the very long delay of the answer.
> I have reproduced the problem on my board.
> My reproducer is https://github.com/montjoie/lava-tests/blob/master/test2a2.py
>
> This problem seems to be here since the v1 of my patchset.
> The vendor driver seems to work so it is not an hardware problem.
>
> I have no clue at the moment, it is hard to diff with vendor driver since it create tty directly and do not use usbserial.
>
> Regards

-- 
David Heidelberg