[U-Boot] uart test

[Michal Suchanek]

On 22 September 2014 09:39, Wolfgang Denk <wd at denx.de> wrote:
> Dear shobin b,
>
> In message <BAY177-W11FCF8C66874E1EC032984B2B30 at phx.gbl> you wrote:
>>
>> Hi,I am using toradex carrier board with colibri t30 module.In that
>> X13 and X14 are uart.first uart X13 is default serial console.In that
>> i need to check the second uart X14. How can i use second uart or how
>> can i check second uart X14.please help me.Regards,shobin.b
>
> Testing peripherals in U-Boot is part of the POST subsystem.
>
> You probably remember that from our discussions from January through
> April this year.
>
> So far, there is no specific UART test available in POST, so you would
> have to add one.
>
> Alternatively, you could just enable the port in question as
> alternative console device, and switch the console to that port and
> try if it works.  Note that it might be difficult to switch back if it
> doesn't work - if that should be a problem, you might consider to also
> enable netconsole.
>

FWIW there was an issue with incorrectly set uart on some sunxi
devices. When you set uart to non-connected pins, set u-boot console
to that uart, and do not set up termination for the pins u-boot will
receive noise on the uart and stop booting thinking that the user
typed something.

That said if the hardware is present and you have 2pin uart (rx/tx)
only and do not use any particular protocol (like, say, ppp which has
some structure) you cannot tell if the uart is usable or not. On 4pin
uarts you can use the additional pins to sense if a device is attached
or not - that's what the pins were for.

Thanks

Michal