linux-kernel - Re: [PATCH v2] arm64: dts: allwinner: h6: Use dummy regulator for Tanix TX6

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Message-ID: <CAJiuCcevho5fGxW+WLHtJAqfYw+desy5-PipBvtz_vbH6EXVPQ@mail.gmail.com>
Date:   Tue, 28 Apr 2020 16:30:06 +0200
From:   Clément Péron <peron.clem@...il.com>
To:     Maxime Ripard <mripard@...nel.org>, Chen-Yu Tsai <wens@...e.org>,
        Rob Herring <robh+dt@...nel.org>
Cc:     linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        devicetree <devicetree@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-sunxi <linux-sunxi@...glegroups.com>,
        Piotr Oniszczuk <warpme@...pl>
Subject: Re: [PATCH v2] arm64: dts: allwinner: h6: Use dummy regulator for
 Tanix TX6

Hi Maxime, Warpme,

On Tue, 28 Apr 2020 at 16:26, Clément Péron <peron.clem@...il.com> wrote:
>
> Tanix TX6 has a fixed regulator. As DVFS is instructed to change
> voltage to meet OPP table, the DVFS is not working as expected.
>
> Avoid to introduce a new dedicated OPP Table where voltage are
> equals to the fixed regulator as it will only duplicate all the OPPs.
> Instead remove the fixed regulator so the DVFS framework will create
> dummy regulator and will have the same behavior.
>
> Add some comments to explain this in the device-tree.

Changes since v1:
I have change this patch to use dummy regulator and add comment about
this choice.
I think it's a bit better than just dropping the regulator.

@Piotr Oniszczuk:
Please add your tested-by tag, to be sure this is working as expected !

Thanks & Regards
Clement

>
> Reported-by: Piotr Oniszczuk <warpme@...pl>
> Fixes: add1e27fb703 ("arm64: dts: allwinner: h6: Enable CPU opp tables for Tanix TX6")
> Signed-off-by: Clément Péron <peron.clem@...il.com>
> ---
>  .../boot/dts/allwinner/sun50i-h6-tanix-tx6.dts | 18 ++++++++++++++++--
>  1 file changed, 16 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/boot/dts/allwinner/sun50i-h6-tanix-tx6.dts b/arch/arm64/boot/dts/allwinner/sun50i-h6-tanix-tx6.dts
> index be81330db14f..3e96fcb317ea 100644
> --- a/arch/arm64/boot/dts/allwinner/sun50i-h6-tanix-tx6.dts
> +++ b/arch/arm64/boot/dts/allwinner/sun50i-h6-tanix-tx6.dts
> @@ -48,7 +48,15 @@
>  };
>
>  &cpu0 {
> -       cpu-supply = <&reg_vdd_cpu_gpu>;
> +       /*
> +        * Don't specify the CPU regulator, as it's a fixed
> +        * regulator DVFS will not work as it is intructed
> +        * to reach a voltage which can't be reached.
> +        * Not specifying a regulator will create a dummy
> +        * regulator allowing all OPPs.
> +        *
> +        * cpu-supply = <&reg_vdd_cpu_gpu>;
> +        */
>  };
>
>  &de {
> @@ -68,7 +76,13 @@
>  };
>
>  &gpu {
> -       mali-supply = <&reg_vdd_cpu_gpu>;
> +       /*
> +        * Don't specify the GPU regulator, see comment
> +        * above for the CPU supply.
> +        *
> +        * mali-supply = <&reg_vdd_cpu_gpu>;
> +        */
> +
>         status = "okay";
>  };
>
> --
> 2.20.1
>