Switching among serial consoles

Tom Rini trini at konsulko.com
Fri Mar 20 19:26:33 CET 2020

On Wed, Mar 18, 2020 at 09:48:36AM +0100, Michal Simek wrote:
> Hi,
> long time ago I was playing with switching among consoles.
> I have two IPs with the same driver where main console is probed and
> used which is visible via dm tree.
>  serial        1  [ + ]   serial_zynq           |   |-- serial at ff000000
>  serial        2  [   ]   serial_zynq           |   |-- serial at ff010000
> then I have also dcc which can be also used as a console
>  serial        0  [   ]   arm_dcc               |-- dcc
> Lastly I have enabled netconsole feature.
> I have no problem to switch between serial at ff000000 and nc but I can't
> switch it to dcc or second instance.
> dhcp
> setenv ncip
> setenv nc 'setenv stdout nc;setenv stdin nc'
> setenv dcc 'setenv stdout dcc;setenv stdin dcc'
> setenv serial0 'setenv stdout serial at ff000000;setenv stdin serial at ff000000'
> setenv serial1 'setenv stdout serial at ff010000;setenv stdin serial at ff010000'
> run nc
> and then via netconsole
> run serial0
> works to get back.
> Console info is showing only available and registered instances.
> ZynqMP> con
> List of available devices:
> serial at ff000000 00000007 IO
> serial   00000003 IO stdin stdout stderr
> nulldev  00000003 IO
> nc       00000003 IO
> It means the question is how to probe second instance of serial_zynq
> serial at ff010000 and dcc. I expect when probe is done it will show up in
> console list and switch is possible.
> I found SERIAL_SEARCH_ALL symbol but it is just search not probe.
> I am quite sure that it was working in past but not sure if this was
> before DM but I would like to know how you are doing it/testing it today.

I think the answer is we don't have any tests for multiple consoles to
start with, so it's not tested.  I'd start by grabbing an old platform
and bisect'ing back the years to see when it did last work as the first
thing.  Sorry!

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