[U-Boot] [PATCH 1/2] serial: mxc: support DTE mode

[Ryan Harkin]

Hi Simon,

On 22 January 2018 at 00:29, Simon Glass <sjg at chromium.org> wrote:

> Hi Ryan,
>
> On 19 January 2018 at 06:21, Ryan Harkin <ryan.harkin at linaro.org> wrote:
> > Hi Stefan,
> >
> > Thanks for looking so quickly.
> >
> > On 19 January 2018 at 12:23, Stefan Agner <stefan.agner at toradex.com>
> wrote:
> >>
> >> Hi Ryan,
> >>
> >>
> >> On 19.01.2018 10:53, Ryan Harkin wrote:
> >> > Add DTE mode support via Kconfig on the MXC uart.
> >>
> >> Make use of the driver model, there DTE is supported already today:
> >> https://lists.denx.de/pipermail/u-boot/2016-July/259573.html
> >
> >
> > My change would be useful for other non-DM users of serial_mxc.c, of
> course.
> > Not just WaRP7.
> >
> > I don't have any objection to WaRP7 moving to DM, although that isn't my
> > call, but moving using the driver model is not a straight-forward
> change, is
> > it? WaRP7 today doesn't use it.
>
> We are planning to require that board use CONFIG_BLK fairly soon, and
> that likely means conversion to device tree I don't think it makes
> sense to accept patches like this. If the board can be converted, then
> let's do it!
>

I'm not the maintainer of this board. I'm only making this patch so I can
put it into our test farm. But I'm interested in giving it a go. In fact, I
started already after Stefan's email. And bricked my board :-)


> >
> > Do you have an example of a board using this driver that switched using
> the
> > driver model? I'd like to see the scale of the changes needed.
>
> It probably requires:
>
> - Adding a DT (with u-boot,dm-pre-reloc as needed)
>

I take it we add the DT from the upstream linux kernel? The upstream DT
doesn't define UART6, the one I want to use. I have a patch for the kernel
that I have not attempted to send upstream yet.

What approach should I take?
- upstream my patch to the kernel first
- use the DT from upstream kernel as-is and add a separate patch in the
u-boot tree
- use the DT from upstream kernel as-is and squash in my patch

Or something else?

Updating the DT from upstream will possibly mean updating the DTs for all
other iMX7 boards [1], because the include/dt-bindings stuff has changed
slightly, as well as the imx7s.dtsi file. I have no way of testing the
other boards, but I guess their maintainers can help there.


- Checking that stdio-path is correct
>

That's probably what bricked my board...

Cheers,
Ryan.

[1] There only appear to be two iMX7 board in u-boot already:
arch/arm/dts/imx7d.dtsi:44:#include "imx7s.dtsi"
arch/arm/dts/imx7-colibri.dts:9:#include "imx7d.dtsi"
arch/arm/dts/imx7d-sdb.dts:9:#include "imx7d.dtsi"



> Regards,
> Simon
>