Re: [PATCH 2/2] ARM: dts: rockchip: add extra cpu opp points to rk3288-miqi

From: "Heiko Stübner" <heiko@sntech.de>
To: Rob Herring <robh+dt@kernel.org>,
	linux-arm-kernel@lists.infradead.org,
	linux-rockchip@lists.infradead.org, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	Demetris Ierokipides <ierokipides.dem@gmail.com>
Cc: Demetris Ierokipides <ierokipides.dem@gmail.com>
Subject: Re: [PATCH 2/2] ARM: dts: rockchip: add extra cpu opp points to rk3288-miqi
Date: Sat, 09 Jan 2021 14:40:55 +0100	[thread overview]
Message-ID: <1680769.VLH7GnMWUR@diego> (raw)
In-Reply-To: <20210108151036.36434-3-ierokipides.dem@gmail.com>

Hi Demetris,

Am Freitag, 8. Januar 2021, 16:10:36 CET schrieb Demetris Ierokipides:
> Add extra 1.7GHz and 1.8GHz opp points to the MiQi device-tree to improve
> performance.
> 
> Signed-off-by: Demetris Ierokipides <ierokipides.dem@gmail.com>
> ---
>  arch/arm/boot/dts/rk3288-miqi.dts | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/arch/arm/boot/dts/rk3288-miqi.dts b/arch/arm/boot/dts/rk3288-miqi.dts
> index 713f55e143c6..1b48855db6ff 100644
> --- a/arch/arm/boot/dts/rk3288-miqi.dts
> +++ b/arch/arm/boot/dts/rk3288-miqi.dts
> @@ -96,6 +96,18 @@ &cpu3 {
>  	cpu-supply = <&vdd_cpu>;
>  };
>  
> +&cpu_opp_table {
> +	opp-1704000000 {
> +		opp-hz = /bits/ 64 <1704000000>;
> +		opp-microvolt = <1350000>;
> +	};
> +
> +	opp-1800000000 {
> +		opp-hz = /bits/ 64 <1800000000>;
> +		opp-microvolt = <1350000>;
> +	};
> +};
> +

sorry, but no .

The OPPs in the mainline kernel match the specifications released by the
soc vendor. Going outside these specs _may_ affect things like stability
on some boards or in general simply the lifetime of the chip itself.

So yes, while boards may generally work with these higher frequencies
I don't think this should be the default coming from the mainline kernel.

If board-owners feel the need to exceed the specs they can still modify
the dts, but we shouldn't force this decision on everyone.

Heiko