Serial console via USB (USBTTY) ...

[Herbert Poetzl]

Hello Andy!

Thanks for the quick feedback!

On Thu, Apr 01, 2021 at 04:10:57PM +0300, Andy Shevchenko wrote:
> On Thu, Apr 1, 2021 at 2:19 PM Herbert Poetzl <herbert at 13thfloor.at> wrote:


>> I'm trying to get a serial console via USB working on
>> STM32MP1 but I'm encountering some problems there ...

>> The u-boot README suggests to add the following config
>> entries to the board specific .h file:

>>  CONFIG_USB_DEVICE
>>  CONFIG_USB_TTY
>>  CONFIG_USBD_HS (for high speed support)
>>  CONFIG_SYS_CONSOLE_IS_IN_ENV

>> ... but when doing so, I get a number of linker errors
>> which suggest that there is something missing:
>> https://pastebin.com/raw/bbpCu8jy

>> Marek (via IRC) suggested that this is because the
>> USB_TTY seems to be based on the old gadget framework
>> and needs to be updated to the new one.

> Precisely!

Are there any examples of such a conversion or is there
some guide how to convert drivers from the 'old' framework
to the 'new' one?

>> It was also suggested that a port of the Linux serial
>> function driver would be a good alternative to get
>> CDC/ACM functionality into u-boot and that Andy might
>> already be working on this ...

> I abandoned that, but I can send what I have (it still doesn't
> properly work to me).

Would definitely be interesting to see, as it seems that
other function drivers (those are the f_* ones, as far
as I understood) seem to work just fine.

>> So my questions are:

>>  - What is currently the best/easiest approach to
>>    get a serial console via USB working?

> Create a support for it. 
> You may consider it as there is no support.

Okay, how do I best start with that?

>>  - Is the port from Linux in a stage that it can
>>    be tested and/or finalized within a easonable
>>    amount of time?

> Not from me (I started but encountered so many issues here and
> there, besides the fact that it's really time consuming).

I understand ...

>>  - Can I help getting this working?

> If you do it yourself. I can help with testing on my platform.

Great! Thanks in advance!

Best,
Herbert

> -- 
> With Best Regards,
> Andy Shevchenko