UART Route setting

[Oskar Senft]

Hi Henbin

I think we should be able to configure default settings for the routing
with the driver that I'm working on. I guess that could be done via DTS or
by just applying settings via /sys during boot.

What do you think?

For my use case, I'll need the setting to be changed back and forth during
runtime from the obmc-console-server.

Oskar.

On Wed, Aug 1, 2018, 8:30 PM Henbin Chang <henbinchang at gmail.com> wrote:

> Hi Oskar,
>
> Thanks your response.
>
> In my machine design, the host uses AST2500 UART2 to implement console
> redirection.
> To make openbmc host consle/ipmi SOL workable, I use the 'local-tty =
> ttyS2' setting and manually change the UART route (UART2<->UART3).
>
> I found  VUART be used for host console after I checked some openpower
> machines. Thus, they didn't meet this problem.
>
> I also tried to look for any related discussion but got nothing.
> To avoid any loss, I sent a mail to ask if any approach to change the UART
> route under openbmc framework.
>
> Currently, I add a hard code (modify HICRA regiser) in u-boot as the
> workaround.
>
> The suggestions you provided are good if the dynamic UART  route changing
> is needed.
>
> I may write a driver to handle the default UART route. It can be
> enabled/disabled and get the the default UART route setting from machine
> dts, and then modify the HICRA register.
>
> Thanks.
> Henbin.
>
> 2018-08-02 0:16 GMT+08:00 Oskar Senft <osk at google.com>:
>
>> Hi Henbin
>>
>> It's funny that you ask, since I had just started to look into the same
>> problem.
>>
>> I'd like to change the UART routing on an AST2500 when a client connects
>> to the obmc-console-server. The use case is to dynamically connect the
>> host's UART to a UART owned by the BMC.
>>
>> I was thinking of writing a kernel driver that would expose the config
>> options from the HICRA register on AST2500 as /sys files. Each file
>> represents the target UART1..5 and IO1..5. The file value represents the
>> source UART1..5 and IO1..5. Not all combinations are supported by the
>> Aspeed, so I'd add the necessary checks and error reporting into the code.
>>
>> An alternative would be to just use /dev/mem to do that, but my
>> understanding is that default support for that is going away or has gone
>> away.
>>
>> Oskar.
>>
>>
>> ---------- Forwarded message ----------
>>> From: Henbin Chang <henbinchang at gmail.com>
>>> Date: Wed, Aug 1, 2018 at 12:11 AM
>>> Subject: UART Route setting
>>> To: OpenBMC Maillist <openbmc at lists.ozlabs.org>
>>>
>>>
>>> Hi,
>>>
>>> Could anyone know how to modify UART Route setting through dts, driver
>>> or other mechanism?
>>>
>>> Or I have to find a point to modify it e.g. board_init() in the u-boot.
>>>
>>> Thanks.
>>>
>>
>
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