Re: [PATCH v2] arm64: dts: allwinner: a64: Enable eMMC on A64-OLinuXino

[Maxime Ripard <maxime.ripard@bootlin.com>]

Hi,

On Wed, Aug 07, 2019 at 08:09:19PM +0800, Chen-Yu Tsai wrote:
> On Wed, Aug 7, 2019 at 8:01 PM Maxime Ripard <maxime.ripard@bootlin.com> wrote:
> >
> > On Tue, Aug 06, 2019 at 02:25:17PM +0800, Chen-Yu Tsai wrote:
> > > On Mon, Aug 5, 2019 at 8:58 PM Martin Ayotte <martinayotte@gmail.com> wrote:
> > > >
> > > > Fine for me too.
> > > >
> > > > Thanks .
> > > >
> > > > -----Message d'origine-----
> > > > De : Sunil Mohan Adapa [mailto:sunil@medhas.org]
> > > > Envoyé : Monday, August 05, 2019 1:25 AM
> > > > Ą : Chen-Yu Tsai
> > > > Cc : Maxime Ripard; Martin Ayotte; linux-arm-kernel
> > > > Objet : Re: [PATCH v2] arm64: dts: allwinner: a64: Enable eMMC on
> > > > A64-OLinuXino
> > > >
> > > > On 04/08/19 8:33 pm, Chen-Yu Tsai wrote:
> > > > > On Fri, Aug 2, 2019 at 2:47 AM Sunil Mohan Adapa <sunil@medhas.org> wrote:
> > > > >>
> > > > >> On 01/08/19 6:49 am, Martin Ayotte wrote:
> > > > >>> If my SOB could help here, I don't mind since I've done the commit
> > > > >>> more than a year ago for Armbian ...
> > > > >>>
> > > > >>> Signed-off-by: Martin Ayotte <martinayotte@gmai.com>
> > > > >>> Tested-by: Martin Ayotte <martinayotte@gmai.com>
> > > > >> gmai.com is likely a typo.
> > > > >>
> > > > >>> On Wed, Jul 31, 2019 at 10:42 PM Chen-Yu Tsai <wens@csie.org
> > > > >>>
> > > > >>>> Thanks. The patch looks good overall. The authorship is a little
> > > > >>>> confusing though. If it was initially done by Martin (CC-ed), then
> > > > >>>> he should be the author, and we should get his Signed-off-by if
> > > > >>>> possible.
> > > > >>
> > > > >> Martin is indeed the original author of the patch. Thank you for
> > > > reviewing.
> > > > >
> > > > > I'd like to apply this patch with Martin as the author, if that's OK with
> > > > you
> > > > > both?
> > > >
> > > > That is completely okay with me.
> > >
> > > Applied for 5.4.
> > >
> > > I reordered the tags so they make more sense:
> > >
> > > https://git.kernel.org/pub/scm/linux/kernel/git/sunxi/linux.git/commit/?h=sunxi/dt-for-5.4&id=0834887732df5af41b59b2e4d530fc1f5478965f
> >
> > Sorry for being late on this, but it looks like the eMMC, NAND and SPI
> > pins are conflicting on the A64-Olinuxino design.
> >
> > There's no configuration with a NAND, so we don't really need to worry
> > about that, but if we merge this in the main DT, we'll prevent anyone
> > from using that DT on an olinuxino with a SPI flash.
> >
> > I think we should just create emmc and SPI-flash variants of that DT.
>
> Actually they aren't. Olimex specifically uses eMMC modules that don't
> use the data strobe line, so SPI can be used together.

Ah, right.

Still, this creates a precedent that I'm not really comfortable
with. Three actually.

Merging this in the main DT means three things:
  - We're not consistent anymore, including within the olinuxino
    boards only. A20 Olinuxino is pretty much in the same situation,
    yet we dealt with it differently.
  - This means that this will create a spurious device and report
    errors in the kernel message and whenever someone will try to
    access the device on boards that don't have it wired. This
    shouldn't happen and we really shouldn't expose devices that just
    aren't there, just like you don't have all the devices that are
    not connected on your USB connector.
  - Finally, this means that in order to keep it somewhat consistent,
    we would have to merge the SPI flash in the main DT too. This will
    prevent people without a SPI flash to use the SPI signals on the
    UEXT connector for something else, which again goes against the
    policy we've had for basically any other board.

Maxime

--
Maxime Ripard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

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