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

[Maxime Ripard]

On Tue, Oct 13, 2020 at 11:27:33PM +0200, Jernej Škrabec wrote:
> Dne petek, 09. oktober 2020 ob 09:36:51 CEST je Maxime Ripard napisal(a):
> > On Thu, Oct 08, 2020 at 10:00:06PM +0200, Clément Péron wrote:
> > > Hi Maxime,
> > > 
> > > Adding linux-sunxi and Jernej Skrabec to this discussion.
> > > 
> > > On Thu, 8 Oct 2020 at 17:10, Maxime Ripard <maxime at cerno.tech> wrote:
> > > >
> > > > Hi Clément,
> > > >
> > > > On Mon, Oct 05, 2020 at 08:47:19PM +0200, Clément Péron wrote:
> > > > > On Mon, 5 Oct 2020 at 11:21, Maxime Ripard <maxime at cerno.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 at gmail.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?
> > > >
> > > > If HS-DDR works, yes, but I assume it doesn't?
> > > 
> > > After discussing with Jernej about this issue, I understood that:
> > > - Automatic delay calibration is not implemented
> > > - We also miss some handling of DDR related bits in control register
> > > 
> > > So none of H5/H6 boards should actually work.
> > > (Some 'lucky' boards seem to work enough to switch to HS200 mode...)
> > > 
> > > To "fix" this the H5 disable the HS-DDR mode in sunxi mmc driver :
> > > https://github.com/torvalds/linux/blob/master/drivers/mmc/host/sunxi-mmc.c#L1409
> > 
> > I find it suspicious that some boards would have traces not good enough
> > for HS-DDR (50MHz in DDR) but would work fine in HS200 (200MHz in SDR).
> > If there's some mismatch on the traces, it will only be worse in HS200.
> 
> FYI, similar situation is also with Tanix TX6 board. Mine works well in HS-DDR 
> mode, but some people reported that it doesn't work for them. The only 
> possible difference could be different eMMC IC. I'll try to confirm that.
> 
> Anyway, I did some tests on OrangePi 3 board which also have eMMC. Both modes 
> (HS-DDR and HS200) are supported and work well.

The Orange Pi 3 has an HS400-capable eMMC ?!

That's really good news, I've initially done the HS200 support on a
custom board I had to give back and couldn't find any board with
HS200/HS400 since.

> Interesting observation is that speed test (hdparm -t) reported 80.58
> MB/sec for HS-DDR mode and 43.40 MB/sec for HS200. As it can be seen
> here, HS-DDR is quicker by a factor of 2, but it should be the other
> way around. Reason for this is that both modes use same base clock and
> thus HS-DDR produces higher speed. If I change f_max to 150 MHz (max.
> per datasheet for SDR @ 1.8 V) then naturally HS200 mode is faster
> (124.63 MB/sec) as HS-DDR as it should be.

If it work fine on the H6, we should set the max-frequency property on
the DT, just like I did on the A64.

> This would be actually correct test for problematic boards but
> unfortunately I don't have it. I also hacked in support for HS400
> (~143 MB/s) and this mode is the only one which really needs
> calibration on my board.
> 
> Two observations from BSP driver:
> 1. Module clock is disabled before adjusting DDR bit and afterwards it's re-
> enabled . That could fix some kind of glitches.
> 2. SDMMC peripheral runs on higher clock than on mainline.
> 
> > And for the delay calibration, iirc, that's only necessary for HS400
> > that we don't support?
> 
> According to BSP driver and its DT, HS200 also needs calibration. However, it 
> seems that using it on lower speed it isn't needed.

Which calibration do you mean? IIRC, the data strobe signal is only used
(optionally) in HS400. The controller might have some internal
calibration for other modes though.

Maxime
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