Re: [PATCH] arm64: rk3399: Add capacity-dmips-mhz attributes

[Robin Murphy <robin.murphy@arm.com>]

Hi Marc,

On 2019-02-24 2:35 pm, Marc Zyngier wrote:
> The RK3399 has the interesting property to be a so called "big-little"
> system, where not all the CPUs are equal (the A53s are much weaker
> than the A72s).
> 
> So far, we're not telling the OS that there is such a difference in
> processing capacity, and Linux assumes that they are equal. Too bad.
> 
> Let's tell the OS about this by using the capacity-dmips-mhz
> property. The values used here are those used on the Juno platform,
> which is quite similar. This leads to the scheduler knowing that
> it can pack more tasks on the A72s, and leads to a better interactive
> experience.
> 
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
> ---
>   arch/arm64/boot/dts/rockchip/rk3399.dtsi | 7 ++++++-
>   1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/boot/dts/rockchip/rk3399.dtsi b/arch/arm64/boot/dts/rockchip/rk3399.dtsi
> index 6cc1c9fa4ea6..7eab31184aee 100644
> --- a/arch/arm64/boot/dts/rockchip/rk3399.dtsi
> +++ b/arch/arm64/boot/dts/rockchip/rk3399.dtsi
> @@ -75,6 +75,7 @@
>   			#cooling-cells = <2>; /* min followed by max */
>   			dynamic-power-coefficient = <100>;
>   			cpu-idle-states = <&CPU_SLEEP &CLUSTER_SLEEP>;
> +			capacity-dmips-mhz = <578>;

Probably better to use the value from Juno r2 (485) which should more 
appropriately represent A53 vs. A72, rather than A53 vs. A57.

>   		};
>   
>   		cpu_l1: cpu@1 {
> @@ -86,6 +87,7 @@
>   			#cooling-cells = <2>; /* min followed by max */
>   			dynamic-power-coefficient = <100>;
>   			cpu-idle-states = <&CPU_SLEEP &CLUSTER_SLEEP>;
> +			capacity-dmips-mhz = <578>;
>   		};
>   
>   		cpu_l2: cpu@2 {
> @@ -97,6 +99,7 @@
>   			#cooling-cells = <2>; /* min followed by max */
>   			dynamic-power-coefficient = <100>;
>   			cpu-idle-states = <&CPU_SLEEP &CLUSTER_SLEEP>;
> +			capacity-dmips-mhz = <578>;
>   		};
>   
>   		cpu_l3: cpu@3 {
> @@ -108,6 +111,7 @@
>   			#cooling-cells = <2>; /* min followed by max */
>   			dynamic-power-coefficient = <100>;
>   			cpu-idle-states = <&CPU_SLEEP &CLUSTER_SLEEP>;
> +			capacity-dmips-mhz = <578>;
>   		};
>   
>   		cpu_b0: cpu@100 {
> @@ -118,7 +122,7 @@
>   			clocks = <&cru ARMCLKB>;
>   			#cooling-cells = <2>; /* min followed by max */
>   			dynamic-power-coefficient = <436>;
> -			cpu-idle-states = <&CPU_SLEEP &CLUSTER_SLEEP>;

Oops.

Otherwise, though, I was on the verge of tackling this myself now that 
my 3399 board is building its own kernels - annoyance at the linking 
bottleneck steadfastly refusing to move off CPU0 (except occasionally to 
another little core) has been growing steadily :) With the nits fixed,

Tested-by: Robin Murphy <robin.murphy@arm.com>

Cheers,
Robin.

> +			capacity-dmips-mhz = <1024>;
>   		};
>   
>   		cpu_b1: cpu@101 {
> @@ -130,6 +134,7 @@
>   			#cooling-cells = <2>; /* min followed by max */
>   			dynamic-power-coefficient = <436>;
>   			cpu-idle-states = <&CPU_SLEEP &CLUSTER_SLEEP>;
> +			capacity-dmips-mhz = <1024>;
>   		};
>   
>   		idle-states {
>