[U-Boot] [PATCH v3 9/9] arm: dts: sunxi: Enumerate MMC2 as MMC1

[Jagan Teki]

On Mon, Jan 21, 2019 at 4:12 PM Chen-Yu Tsai <wens at csie.org> wrote:
>
> On Mon, Jan 21, 2019 at 6:32 PM Jagan Teki <jagan at amarulasolutions.com> wrote:
> >
> > Environment and fastboot MMC devices are configured based number
> > of mmc slots defined on particular board in sunxi platform.
> >
> > If number of slots are not more than 1, it assigns 0 which usually mmc
> > device on SD slot. With DM_MMC it is detected as 0 since mmc0 node always
> > be an mmc device.
> >
> > If number of slots are more than 1, it assigns 1 which assumes 0 is mmc
> > device and 1 is emmc device. But with DM_MMC there is chance of detecting
> > emmc as device 2 since mmc1 is SDIO as per devicetree definition.
> >
> > So override mmc2 to mmc1 in sunxi dtsi, this will eventually detect mmc2
> > as mmc 1 device even if the board dts has mmc0, mmc1, mmc2.
> >
> > Some platforms like A20 has mmc0...mmc3, but there is no usecases now for
> > enabling all mmc controllers in any of A20 board dts files.
> >
> > Signed-off-by: Jagan Teki <jagan at amarulasolutions.com>
> > ---
> >  arch/arm/dts/sunxi-u-boot.dtsi | 4 ++++
> >  1 file changed, 4 insertions(+)
> >
> > diff --git a/arch/arm/dts/sunxi-u-boot.dtsi b/arch/arm/dts/sunxi-u-boot.dtsi
> > index 8a9f2a6417..fdd4c80aa4 100644
> > --- a/arch/arm/dts/sunxi-u-boot.dtsi
> > +++ b/arch/arm/dts/sunxi-u-boot.dtsi
> > @@ -1,6 +1,10 @@
> >  #include <config.h>
> >
> >  / {
> > +       aliases {
> > +               mmc1 = &mmc2;
> > +       };
> > +
> >         binman {
> >                 filename = "u-boot-sunxi-with-spl.bin";
> >                 pad-byte = <0xff>;
> > --
> > 2.18.0.321.gffc6fa0e3
> >
>
> Slightly curious. What happens when mmc1 (the real mmc1) is enabled
> and probes before mmc2 does? Does it take mmc1? What happens then
> when mmc2 probes and wants mmc1?

Existing sunxi code has MMC_SUNXI_SLOT_EXTRA if the board has second
MMC device, like eMMC which make default env or fastboot device as 1.
But with DT definitions eMMC can be probed as mmc2 which can fail to
get env and fastboot setups.

This override mmc2 to as mmc1 can satisfy the existing code
identification. I did many code changes to get rid of DT changes but
it became hard to get via those[1], patch 27 to 31

>
> Also, on the A31, we use mmc3 instead of mmc2 for eMMC. Only mmc3
> supports DDR transfer modes.

Yes, but as per current usage no board is using all together, if some
board is using then, it's their duty to enable the same via defconfig
in future.

[1] https://patchwork.ozlabs.org/cover/959324/