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

[Yao Zi <ziyao@disroot.org>]

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