[PATCH/RFC v2 0/2] arm64: dts: r8a7795: Add support for R-Car H3 ES2.0

[Geert Uytterhoeven]

Hi Sjoerd,

On Thu, Mar 30, 2017 at 1:50 PM, Sjoerd Simons
<sjoerd.simons at collabora.co.uk> wrote:
> On Thu, 2017-03-30 at 13:13 +0200, Geert Uytterhoeven wrote:
>> On Thu, Mar 30, 2017 at 12:48 PM, Sjoerd Simons
>> <sjoerd.simons at collabora.co.uk> wrote:
>> > On Fri, 2017-03-24 at 14:37 +0100, Geert Uytterhoeven wrote:
>> > > This patch series adds preliminary support for Renesas Salvator-X
>> > > development boards equipped with revision ES2.0 of the R-Car H3
>> > > Soc.
>> > >
>> > >   - Patch 1 adds support for the R-Car H3 ES2.0 Soc,
>> > >     While this patch is safe as-is, as it doesn't affect any
>> > > existing
>> > >     setups, it's probably a bit premature to apply it.
>> > >   - Patch 2 adds support for Salvator-X boards with R-Car H3
>> > > ES2.0.
>> > >     This patch does affect existing development setups, as it
>> > > changes
>> > > the
>> > >     name of the DTB for Salvator-X boards equipped with ES1.x
>> > > SoCs.
>> > >     Given most developers have access to ES1.x only, this patch
>> > > must
>> > > not be
>> > >     applied yet.
>> >
>> > Would it make more sense to add a new r8a7795-es2.dtsi and keep the
>> > current dtsi for es1? Having to load different device-trees based
>> > on
>> > which kernel is used would be rather nasty.
>>
>> We definitely considered that option.
>> However, we concluded that in the end, we want to mainly support
>> production
>> SoCs.  Hence the default files should represent the production
>> version.
>> Using a preproduction SoC can be considered a special case, and thus
>> needs
>> a file with a special esX ID in its name.
>
> The problem is that even though they are pre-production, these are out
> there and in active use, e.g. kernelci is at least doing automated
> testing on one of those in Kevins lab and should be an additional
> soonish in the Collabora lab.
>
> And for developers it'll be extra fun if halfway through a bisect the
> dts name changes..
>
> Having a es2 in your dtb name might be a bit quirky, but it's really
> just a name without other meaning :).
>
>> We do realize this can cause some inconveniences during the
>> transition period,
>> when most developers don't have access to ES2.0 SoCs yet, or have
>> mixed
>> environments of ES1.x and ES2.0.
>
> Heh yeah, i'd expect we'd have a mixed environment for quite a while
> given these boards are a bit too expensive to just throw in the trash..
>
>> Of course you can keep on using the current DTB (binary) on your H3
>> ES1.x
>> boards, as long as you don't need to use devices not yet described in
>> that DTB.

We can keep on discussing this for a while, this is definitely v4.13+ material.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds