Re: [PATCH 8/8] arm64: dts: rockchip: Enable SD-card interface on Radxa E20C

Yao Zi
2025-03-01T15:17:52Z

On Sat, Mar 01, 2025 at 02:01:05PM +0100, Jonas Karlman wrote:
> Hi,
>
> On 2025-03-01 11:48, Yao Zi wrote:
> > SD-card is available on Radxa E20C board.
> >
> > Signed-off-by: Yao Zi <ziyao@disroot.org>
> > ---
> > arch/arm64/boot/dts/rockchip/rk3528-radxa-e20c.dts | 14 ++++++++++++++
> > 1 file changed, 14 insertions(+)
> >
> > diff --git a/arch/arm64/boot/dts/rockchip/rk3528-radxa-e20c.dts b/arch/arm64/boot/dts/rockchip/rk3528-radxa-e20c.dts
> > index d2cdb63d4a9d..473065aa4228 100644
> > --- a/arch/arm64/boot/dts/rockchip/rk3528-radxa-e20c.dts
> > +++ b/arch/arm64/boot/dts/rockchip/rk3528-radxa-e20c.dts
> > @@ -12,6 +12,10 @@ / {
> > model = "Radxa E20C";
> > compatible = "radxa,e20c", "rockchip,rk3528";
> >
> > + aliases {
> > + mmc0 = &sdmmc;
>
> Suggest using mmc1 for sd-card because the e20c typically have onboard
> emmc, compared to removable sd-card.

My board doesn't have an eMMC: it's optional as well, but all variants
of Radxa E20C come with an SD-card interface. The vendor devicetree sets
sdmmc as mmc0 as well[1].

I won't insist on it and am willing to take the change if you still
consider mmc0 is better.

> > + };
> > +
> > chosen {
> > stdout-path = "serial0:1500000n8";
> > };
> > @@ -20,3 +24,13 @@ chosen {
> > &uart0 {
> > status = "okay";
> > };
> > +
> > +&sdmmc {
> > + bus-width = <4>;
> > + cap-mmc-highspeed;
> > + cap-sd-highspeed;
> > + disable-wp;
> > + rockchip,default-sample-phase = <90>;
> > + sd-uhs-sdr104;
>
> Are you sure uhs-sdr104 works as is should?

In fact yes, tuning succeeds at 148.5MHz and results in 66MB/s reading
speed.

> Vendor kernel use a different "v2" tuning

This isn't a problem. IMHO V2 tuning is more like a quick path, which
tries inheritting the phase from firmware and then re-tunes roughly.
Fine tunning is still a fallback here in case of failure, see the commit
message in the downstream kernel[2]. And testing proves it's okay for
RK3528 to issue fine-tuning always.

> and this is also missing the vccio_sd vqmmc-supply to switch between
> 3v3 and 1v8.

But this is a problem, thanks for catching it! Somehow my card managed
to run at 148.5MHz with 3v3 voltage level, but it's definitely a
compatiblity issue. I'm surprised that the driver doesn't complain when
switching to SDR modes without a regulator configured.

> You could add following regulator for sdmmc:
>
> vccio_sd: regulator-vccio-sd {
> compatible = "regulator-gpio";
> gpios = <&gpio4 RK_PB6 GPIO_ACTIVE_HIGH>;
> pinctrl-names = "default";
> pinctrl-0 = <&sdmmc_vol_ctrl_h>;
> regulator-name = "vccio_sd";
> regulator-min-microvolt = <1800000>;
> regulator-max-microvolt = <3300000>;
> states = <1800000 0x0>, <3300000 0x1>;
> };
>
> and following pinctrl:
>
> sdmmc {
> sdmmc_vol_ctrl_h: sdmmc-vol-ctrl-h {
> rockchip,pins = <4 RK_PB6 RK_FUNC_GPIO &pcfg_pull_none>;
> };
> };
>
> add then the power supplies to the sdmmc node:
>
> vmmc-supply = <&vcc_3v3>;
> vqmmc-supply = <&vccio_sd>;
>
> That matches the schematics for e20c, and works when testing non-uhs modes.

Thanks for the hints. Will rebase on your pinctrl series and get
regulators and pinctrl settings applied in the next version.

> Regards,
> Jonas
>
> > + status = "okay";
> > +};
>

Cheers,
Yao Zi

[1]: https://github.com/radxa/kernel/blob/2b0c8de7dc4c68947cda206dcc2e457e9677e426/arch/arm64/boot/dts/rockchip/rk3528-radxa-e20c.dts#L22-L26
[2]: https://github.com/rockchip-linux/kernel/commit/795e052cc8610aa59a64b104f975cc4a45493d5d