Re: [PATCH] pinctrl: sh-pfc: r8a7796: Add group for AVB MDIO and MII pins

[Geert Uytterhoeven <geert@linux-m68k.org>]

On Tue, May 2, 2017 at 4:33 PM, Niklas Söderlund
<niklas.soderlund@ragnatech.se> wrote:
> On 2017-04-20 13:47:19 +0200, Geert Uytterhoeven wrote:
>> On Thu, Apr 20, 2017 at 1:44 PM, Laurent Pinchart
>> <laurent.pinchart@ideasonboard.com> wrote:
>> > On Thursday 20 Apr 2017 13:37:27 Geert Uytterhoeven wrote:
>> >> On Thu, Apr 20, 2017 at 12:18 PM, Laurent Pinchart wrote:
>> >> > On Thursday 20 Apr 2017 12:11:41 Geert Uytterhoeven wrote:
>> >> >> On Thu, Apr 20, 2017 at 12:02 PM, Laurent Pinchart wrote:
>> >> >>> On Thursday 20 Apr 2017 11:49:06 Geert Uytterhoeven wrote:
>> >> >>>> Group the AVB pins into similar groups as found in other
>> >> >>>> sh-pfc
>> >> >>>> drivers. The pins can not be muxed between functions other than AVB,
>> >> >>>> but their drive strengths can be controlled.
>> >> >>>>
>> >> >>>> The group avb_mdc containing ADV_MDC and ADV_MDIO is called avb_mdio
>> >> >>>> on other SoCs. In pfc-r8a7796 the avb_mdc group already existed and is
>> >> >>>> in use in DT. Therefore add the ADV_MDIO pin to the existing group
>> >> >>>> instead of renaming it.
>> >> >>>
>> >> >>> This clearly shows that we need a few kernel releases to test
>> >> >>> PFC-related code and DT before we can commit to an ABI. How do you
>> >> >>> think we should handle this ?
>> >> >>
>> >> >> That's a difficult question
>> >> >>
>> >> >> For now I'd like to treat R-Car M3-W the same as H3.
>> >> >
>> >> > I still believe we should introduce some kind of unstable period for DT
>> >> > bindings, during which they will be merged in mainline but still subject
>> >> > to modification. It could just be a few kernel releases.
>> >>
>> >> Like, from v4.4 (when avb_mdc was added for H3) until v4.12 (earliest
>> >> we can correct this)?
>> >
>> > Sorry, I misread you, I thought that H3 named the group mdio (you might want
>> > to clarify this in the commit message). I was referring to when M3 PFC support
>>
>> Sorry, this was a bit unclear (I reused the description from the H3 patch).
>> This was actually referring to R-Car Gen2. Will fix.
>>
>> > was introduced, which was v4.10, so that's just two releases. We obviously
>> > can't rename mdc to mdio on H3 if we want to keep backward compatibility.
>>
>> And because of pin-compatibility and board sharing of H3 and M3-W, I
>> want both to use identical group naming.
>
> I also think it's a benefit if the group names are identical on H3 and
> M3-W. And I think it is unfortunate that the name do not match Gen2
> naming.
>
> When adding the pins to r8a7795 I thought of instead adding AVB_MDIO to
> the group avb_mdc add a new group with the Gen2 naming (avb_mdio) and
> add both AVB_MDC and AVB_MDIO to this group but still also keep the
> group avb_mdc. If I had done that it would be compatible with Gen2
> naming and backward compatible with old H3 DT. Maybe I was wrong of not
> doing it like this and perhaps that solution should be revisited? That
> is keep avb_mdc as is on H3 for backward compatibility but add avb_mdio to
> both H3 and M3-W and update H3 DT to use avb_mdio.

We can do that later... For now I like to move forward with M3-W like H3.

> In any case I reviewed the pins as it is identical to how it's done on
> H3. So if you choose to move forward with this approach feel free to
> add:
>
> Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>

Thanks, applied to sh-pfc-for-v4.13 with reference to R-Car Gen2 SoC
and Reviewed-by.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@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