linux-kernel - Re: [PATCH 3/3] arm64: dts: rockchip: set rk3399 dynamic CPU power coefficients

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Message-ID: <20170623184956.GA107165@google.com>
Date:   Fri, 23 Jun 2017 11:49:57 -0700
From:   Brian Norris <briannorris@...omium.org>
To:     Heiko Stuebner <heiko@...ech.de>
Cc:     linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Caesar Wang <wxt@...k-chips.com>,
        Doug Anderson <dianders@...omium.org>,
        linux-arm-kernel@...ts.infradead.org,
        Matthias Kaehlcke <mka@...omium.org>
Subject: Re: [PATCH 3/3] arm64: dts: rockchip: set rk3399 dynamic CPU power
 coefficients

On Fri, Jun 23, 2017 at 08:39:25PM +0200, Heiko Stuebner wrote:
> Am Freitag, 23. Juni 2017, 10:07:37 CEST schrieb Brian Norris:
> > Provide the dynamic power coefficient of the big and little CPU
> > clusters. These numbers are currently in use on the Samsung Chromebook
> > Plus ("Kevin").
> > 
> > The power allocator thermal governor doesn't know how to do anything if
> > it doesn't get power parameters from its cooling devices (in this case,
> > CPUfreq). So this effectively enables the power-allocator governor.
> > 
> > Signed-off-by: Brian Norris <briannorris@...omium.org>
> > ---
> >  arch/arm64/boot/dts/rockchip/rk3399.dtsi | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/arch/arm64/boot/dts/rockchip/rk3399.dtsi b/arch/arm64/boot/dts/rockchip/rk3399.dtsi
> > index 69c56f7316c4..4f6667547814 100644
> > --- a/arch/arm64/boot/dts/rockchip/rk3399.dtsi
> > +++ b/arch/arm64/boot/dts/rockchip/rk3399.dtsi
> > @@ -109,6 +109,7 @@
> >  			reg = <0x0 0x0>;
> >  			enable-method = "psci";
> >  			#cooling-cells = <2>; /* min followed by max */
> > +			dynamic-power-coefficient = <100>;
> >  			clocks = <&cru ARMCLKL>;
> >  		};
> >  
> > @@ -142,6 +143,7 @@
> >  			reg = <0x0 0x100>;
> >  			enable-method = "psci";
> >  			#cooling-cells = <2>; /* min followed by max */
> > +			dynamic-power-coefficient = <100>;
> >  			clocks = <&cru ARMCLKB>;
> >  		};
> >  
> > 
> 
> I think these should be set for all cores, similar to clocks. While
> cpufreq and friends regularly only take the first number, in a
> hw-description sense, it should be part of every core in the dt.

It's kinda paired with the cooling information (e.g., #cooling-cells)
which are only present in the first CPU in the cluster, currently.

I can copy this definitely real, empirical value into the other CPUs if
you really think that's necessary :)

Brian