[linux-sunxi] [PATCH] Disable HS-DDR mode for Olimex A64-OLinuXino variants with eMMC

[Clément Péron]

Hi Maxime,

On Thu, 22 Oct 2020 at 11:13, Maxime Ripard <maxime at cerno.tech> wrote:
>
> Hi,
>
> On Thu, Oct 22, 2020 at 09:52:29AM +0200, Clément Péron wrote:
> > Hi Philipp,
> >
> > On Thu, 22 Oct 2020 at 00:10, Philip Rinn <rinni at inventati.org> wrote:
> > >
> > > Hi,
> > >
> > > the Olimex A64-OLinuXino board comes in various variants, three with eMMC.
> > > While MMC HS-DDR mode works fine on one of them (A64-OLinuXino-1Ge4GW) it
> > > doesn't work on the A64-OLinuXino-2Ge8G-IND variant (I don't have the
> > > third variant so I can't check if it works there).
> >
> > We got similar situations for Allwinner H6 (Beelink GS1 and Tanix TX6).
> >
> > There is definitely an issue in the MMC sunxi driver with HS-DDR mode
> > and it's not limited to "olimex,a64-olinuxino-emmc".
> >
> > Have a look at this this message posted by Jernej:
> > https://www.spinics.net/lists/arm-kernel/msg846093.html
> >
> > I think we should disable the HS-DDR mode for A64 / H6 like it's done
> > for H5 and not disable board per board until the issue is resolved.
>
> I'm not opposed to that on principle, but "it doesn't work on some
> board" is not a proper justification to do so. It does on some others,
> so surely there's more to it and this would just paper over whatever
> issue we have instead of properly fixing it.

Maybe the term board is not correct, maybe it's the eMMC chip which is
different.
I don't know if all Beelink GS1/Tanix TX6 use the same eMMC chip for
all the boards.

>
> > If you want to disable only for your board you can set in your
> > device-tree: mmc-hs200-1_8v; This will switch to HS200 mode without
> > using the HS-DDR mode.
>
> Sigh. Can we at least work on a fix instead of providing terrible
> workarounds?

I agree with you on this, but my board doesn't have this issue and I
tried to read the vendor kernel and spot a difference but didn't find
anything relevant.

Regards,
Clement

>
> Maxime