Re: [linux-sunxi] [PATCH 5/7] arm64: dts: allwinner: A64: Limit MMC2 bus frequency to 150 MHz

[Chen-Yu Tsai <wens@xxxxxxxx>]

On Wed, Jan 6, 2021 at 11:06 PM Andre Przywara <andre.przywara@xxxxxxx> wrote:
>
> In contrast to the H6 (and later) manuals, the A64 datasheet does not
> specify any limitations in the maximum possible frequency for eMMC
> controllers.
> However experimentation has found that a 150 MHz limit similar to other
> SoCs and also the MMC0 and MMC1 controllers on the A64 seems to exist
> for the MMC2 controller.
>
> Limit the frequency for the MMC2 controller to 150 MHz in the SoC .dtsi.
> The Pinebook seems to be the an odd exception, since it apparently seems
> to work with 200 MHz as well, so overwrite this in its board .dts file.
>
> Tested on a Pine64-LTS: 200 MHz HS-200 fails, 150 MHz HS-200 works.
>
> Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>

Please add a fixes tag. This helps with finding the original commit
that introduced the issue and backporting.

This would benefit SoPine / Pine64-LTS users that are using eMMC.

ChenYu

> ---
>  arch/arm64/boot/dts/allwinner/sun50i-a64-pinebook.dts | 1 +
>  arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi         | 2 +-
>  2 files changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/boot/dts/allwinner/sun50i-a64-pinebook.dts b/arch/arm64/boot/dts/allwinner/sun50i-a64-pinebook.dts
> index d07cf05549c3..7ae16541d14f 100644
> --- a/arch/arm64/boot/dts/allwinner/sun50i-a64-pinebook.dts
> +++ b/arch/arm64/boot/dts/allwinner/sun50i-a64-pinebook.dts
> @@ -167,6 +167,7 @@
>         pinctrl-0 = <&mmc2_pins>, <&mmc2_ds_pin>;
>         vmmc-supply = <&reg_dcdc1>;
>         vqmmc-supply = <&reg_eldo1>;
> +       max-frequency = <200000000>;
>         bus-width = <8>;
>         non-removable;
>         cap-mmc-hw-reset;
> diff --git a/arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi b/arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi
> index 19e9b8ca8432..57786fc120c3 100644
> --- a/arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi
> +++ b/arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi
> @@ -514,7 +514,7 @@
>                         resets = <&ccu RST_BUS_MMC2>;
>                         reset-names = "ahb";
>                         interrupts = <GIC_SPI 62 IRQ_TYPE_LEVEL_HIGH>;
> -                       max-frequency = <200000000>;
> +                       max-frequency = <150000000>;
>                         status = "disabled";
>                         #address-cells = <1>;
>                         #size-cells = <0>;
> --
> 2.17.5
>
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