Re: [PATCH] ARM: MXS: duckbill: set duart to serial0

[Sascha Hauer <s.hauer@pengutronix.de>]

On Fri, May 29, 2020 at 03:56:53PM +0200, Lucas Stach wrote:
> Am Freitag, den 29.05.2020, 14:51 +0200 schrieb Michael Grzeschik:
> > In the imx28.dtsi the serial0 is set to auart0 which is not the one
> > used on the duckbill. We set duart to serial0 so the console will be
> > properly set.
> 
> If the aliases are the same in the Barebox and Linux DTs there should
> be no need to override the alias numbering in the individual board DTs.
> 
> Is the Linux driver ignoring the alias, or what is the issue being
> fixed here?

There are two different UARTs on the i.MX23/28, the duart ends up as
ttyAMAx in the kernel, the auart as ttyAPPx. Both drivers honor the
alias in the device tree. The upstream dtsi has:

                serial0 = &auart0;
                serial1 = &auart1;
                serial2 = &auart2;
                serial3 = &auart3;
                serial4 = &auart4;

With this we can't assign an alias to the duart anymore, serial0 is
already used. We could add a serial5 alias, but then we would get
ttyAMA5 instead of the desired ttyAMA0.

barebox tries to get an alias for the duart to set the proper console=
string for it. Now Michael changes the serial0 alias from &auart0 to
&duart. With this barebox can assign the correct console= string. Would
Linux be started with this device tree, &auart0 would still end up with
ttyAPP0 because it's the first free one.

This looks awful, but works for now. We are open for better suggestions
;)

Regards,
 Sascha


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