On 2015-06-07, Ian Campbell wrote:
> On Mon, 2015-05-04 at 12:01 -0700, Vagrant Cascadian wrote:
>> I can confirm that wandboard, cubox-i and hummingboard all default to
>> console=ttymxc0, and several other boards by grepping through u-boot's
>> include/configs. Some actually do "setenv bootargs
>> console=ttymxc0,${baudrate}" before their various boot commands.
>>
>> If you prefer a more specific comment, maybe "Workaround lack of
>> baudrate included with console on various iMX systems (e.g. wandboard,
>> cubox-i, hummingboard)." An exhaustive list might prove more trouble
>> than it's worth. :)
>
> For sure!
>
> I was thinking about this some more and it occurred to me that
> console=ttymxc0 (or indeed any console=ttyFOO) ought really to be
> inheriting the existing baud rate etc settings from the bootloader and
> Just Work(tm).
It defaults to 9600 baud (u-boot defaults to 115200), and consequently
the serial console looks like gibberish.
> That lead me to drivers/tty/serial/imx.c:imx_console_get_options() in
> the kernel which is called if no options are given.
>
> That code has been there since the beginning of git history. Did you try
> with just console=ttymxc0 and it didn't work? (Sorry if this is a silly
> question, I think many people don't realise the baud etc is optional so
> it never gets tried).
>
> If you've tried without and it doesn't work then either that code isn't
> called when I think, or it is broken. In either case I'm not too
> inclined to investigate further than "does console=ttymxc0 work" and if
> not then apply that bit of the patch.
I haven't investigated the kernel code, but my experience shows that
without specifying the baud rate it defaults to 9600.
9600 baud seems a bit antiquated at this point... :)
live well,
vagrant
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