linux-kernel - Re: [PATCH v2] arm64: dts: allwinner: h6: add eMMC voltage property for Beelink GS1

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Date:   Mon, 5 Oct 2020 20:47:19 +0200
From:   Clément Péron <peron.clem@...il.com>
To:     Maxime Ripard <maxime@...no.tech>
Cc:     Rob Herring <robh+dt@...nel.org>, Chen-Yu Tsai <wens@...e.org>,
        devicetree <devicetree@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] arm64: dts: allwinner: h6: add eMMC voltage property
 for Beelink GS1

Hi Maxime,


On Mon, 5 Oct 2020 at 11:21, Maxime Ripard <maxime@...no.tech> wrote:
>
> Hi Clément,
>
> On Sat, Oct 03, 2020 at 11:20:01AM +0200, Clément Péron wrote:
> > Sunxi MMC driver can't distinguish at runtime what's the I/O voltage
> > for HS200 mode.
>
> Unfortunately, that's not true (or at least, that's not related to your patch).
>
> > Add a property in the device-tree to notify MMC core about this
> > configuration.
> >
> > Fixes: 089bee8dd119 ("arm64: dts: allwinner: h6: Introduce Beelink GS1 board")
> > Signed-off-by: Clément Péron <peron.clem@...il.com>
> > ---
> >  arch/arm64/boot/dts/allwinner/sun50i-h6-beelink-gs1.dts | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/arch/arm64/boot/dts/allwinner/sun50i-h6-beelink-gs1.dts b/arch/arm64/boot/dts/allwinner/sun50i-h6-beelink-gs1.dts
> > index 049c21718846..3f20d2c9bbbb 100644
> > --- a/arch/arm64/boot/dts/allwinner/sun50i-h6-beelink-gs1.dts
> > +++ b/arch/arm64/boot/dts/allwinner/sun50i-h6-beelink-gs1.dts
> > @@ -145,6 +145,7 @@ &mmc2 {
> >       vqmmc-supply = <&reg_bldo2>;
> >       non-removable;
> >       cap-mmc-hw-reset;
> > +     mmc-hs200-1_8v;
> >       bus-width = <8>;
> >       status = "okay";
> >  };
>
> I'm not really sure what you're trying to fix here, but as far as MMC
> goes, eMMC's can support io voltage of 3.3, 1.8 and 1.2V. Modes up until
> HS DDR (50MHz in DDR) will use an IO voltage of 3.3V, higher speed modes
> (HS200 and HS400) supporting 1.8V and 1.2V.

Some users report that the eMMC is not working properly on their
Beelink GS1 boards.

>
> The mmc-hs200-1_8v property states that the MMC controller supports the
> HS200 mode at 1.8V. Now, I can only assume that since BLDO2 is set up at
> 1.8V then otherwise, the MMC core will rightfully decide to use the
> highest supported mode. In this case, since the driver sets it, it would
> be HS-DDR at 3.3V, which won't work with that fixed regulator.
>
> I can only assume that enabling HS200 at 1.8V only fixes the issue you
> have because otherwise it would use HS-DDR at 3.3V, ie not actually
> fixing the issue but sweeping it under the rug.
>
> Trying to add mmc-ddr-1_8v would be a good idea

Thanks for the explanation, this is indeed the correct one.
So It looks like the SDIO controller has an issue on some boards when
using HS-DDR mode.

Is this patch acceptable with the proper commit log?

It looks like the same issue is happening on A64 Pinebook board.

Thanks
Clement


>
> Maxime