[PATCH 1/2] ARM: ux500: define serial port aliases

[Linus Walleij]

On Sun, Jul 12, 2015 at 11:02 PM, Arnd Bergmann <arnd at arndb.de> wrote:
> On Friday 10 July 2015 11:32:15 Linus Walleij wrote:
>> This enumerates the PL011 serial ports on the Ux500. This is
>> necessary to do if we want to remove one of the serial ports,
>> since userspace depends on console to be present on ttyAMA2
>> and we must not break userspace.
>>
>> Cc: Ulf Hansson <ulf.hansson at linaro.org>
>> Signed-off-by: Linus Walleij <linus.walleij at linaro.org>
>> ---
>> ChangeLog v1->v2:
>> - Moved the alias definitions from the core SoC file
>>   to the toplevel DTS file, as requested by Arnd.
>>
>>
>
> Do all of the boards expose all three uarts in the same order?

Yes and that is the reason the patch series needs this one
to come first.

What happened historically was that userspace was hard-coded
to use ttyAMA2 as console. So for this reason, all boards had
to define ttyAMA0, 1, 2 in their board file (later device tree) so they
would be enumerated in the right order, relying on the DT to
be parsed top to bottom of course.

So when I realized (in patch 2/2) that ttyAMA1 was not really
used on some boards, it was impossible to remove it
as userspace relied on the enumeration.

However I have to remove ttyAMA1 because it is fundamentally
wrong (the RC pin is used for MMC!). Incidentally it worked
to steal

But that breaks userspace since