Re: [PATCH RFC 09/15] ARM: dts: sun6i: sina31s: Switch to mmc3 for onboard eMMC

[Hans de Goede]

Hi,

On 21-01-16 13:28, Chen-Yu Tsai wrote:
> On Thu, Jan 21, 2016 at 8:25 PM, Hans de Goede <hdegoede@xxxxxxxxxx> wrote:
> > Hi,
> >
> > On 21-01-16 13:23, Chen-Yu Tsai wrote:
> > > On Thu, Jan 21, 2016 at 7:16 PM, Hans de Goede <hdegoede@xxxxxxxxxx>
> > > wrote:
> > > > Hi,
> > > >
> > > > On 21-01-16 06:26, Chen-Yu Tsai wrote:
> > > > > According to Allwinner, only mmc3 supports 8 bit DDR transfers for eMMC.
> > > > > Switch to mmc3 for the onboard eMMC, and also assign vqmmc for signal
> > > > > voltage sensing/switching, and "cap-mmc-hw-reset" to denote this
> > > > > instance can use eMMC hardware reset.
> > > >
> > > >
> > > >
> > > > This is going to need some more explanation, does this mean
> > > > that the old dtsi is wrong and the emmc does not work there are all ?
> > >
> > >
> > > mmc2 works fine for either 4 bit SDR/DDR or 8 bit SDR only. It does
> > > not work for 8 bit DDR. I actually tested all the above combinations.
> > >
> > > Also see
> > > https://groups.google.com/d/msg/linux-sunxi/pMzwMWwLALw/6WGgCN1eAQAJ
> > >
> > > About old DTs not working:
> > >
> > > a) The old DT will not work with the mmc patches, as it will try 8 bit DDR
> > >      and fail. Also, the old DT does not use the highest drive strength for
> > >      the mmc pins, meaning it might not work for the other chip families.
> > >
> > > b) Old DT + old kernel works fine (8 bit high-speed), just slower.
> > >
> > > An alternative would be to drop MMC_CAP_1_8V_DDR from the driver, and
> > > use the "mmc-ddr-1_8v" DT capability flag at the dtsi or board level.
> > > There's no real way to describe "don't use 8 bit with MMC DDR" in the DT.
> >
> >
> > OK, so what is confusing me, is how can we choose between the emmc being
> > connected to mmc2 resp mmc3, are there dipswitches on the board? Or can both
> > mmc controllers be routed to the outside on the same port/pins ?
>
> They are on the same pins, just with a different mux value/function.
> I believe the previous patch explains this.

Ah yes, I see the remark about them sharing pins in the previous
patch commit msg now, weird.

Regards,

Hans


> ChenYu
>
> > Regards,
> >
> > Hans
> >
> >
> >
> > > Regards
> > > ChenYu
> > >
> > > > Regards,
> > > >
> > > > Hans
> > > >
> > > >
> > > >
> > > > > Signed-off-by: Chen-Yu Tsai <wens@xxxxxxxx>
> > > > > ---
> > > > >     arch/arm/boot/dts/sun6i-a31s-sina31s-core.dtsi | 6 ++++--
> > > > >     1 file changed, 4 insertions(+), 2 deletions(-)
> > > > >
> > > > > diff --git a/arch/arm/boot/dts/sun6i-a31s-sina31s-core.dtsi
> > > > > b/arch/arm/boot/dts/sun6i-a31s-sina31s-core.dtsi
> > > > > index ea69fb8ad4d8..4ec0c8679b2e 100644
> > > > > --- a/arch/arm/boot/dts/sun6i-a31s-sina31s-core.dtsi
> > > > > +++ b/arch/arm/boot/dts/sun6i-a31s-sina31s-core.dtsi
> > > > > @@ -61,12 +61,14 @@
> > > > >     };
> > > > >
> > > > >     /* eMMC on core board */
> > > > > -&mmc2 {
> > > > > +&mmc3 {
> > > > >           pinctrl-names = "default";
> > > > > -       pinctrl-0 = <&mmc2_8bit_emmc_pins>;
> > > > > +       pinctrl-0 = <&mmc3_8bit_emmc_pins>;
> > > > >           vmmc-supply = <&reg_dcdc1>;
> > > > > +       vqmmc-supply = <&reg_dcdc1>;
> > > > >           bus-width = <8>;
> > > > >           non-removable;
> > > > > +       cap-mmc-hw-reset;
> > > > >           status = "okay";
> > > > >     };