linux-kernel - Re: [PATCH] arm64: dts: rockchip: Explicitly set pclk_pmu

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Date:   Mon, 29 Aug 2016 11:18:42 -0700
From:   Brian Norris <briannorris@...omium.org>
To:     Douglas Anderson <dianders@...omium.org>
Cc:     Heiko Stuebner <heiko@...ech.de>,
        linux-rockchip@...ts.infradead.org, zhengxing@...k-chips.com,
        robh+dt@...nel.org, mark.rutland@....com, catalin.marinas@....com,
        will.deacon@....com, wxt@...k-chips.com, jay.xu@...k-chips.com,
        zhangqing@...k-chips.com, david.wu@...k-chips.com,
        yamada.masahiro@...ionext.com, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64: dts: rockchip: Explicitly set pclk_pmu_src on
 rk3399

On Mon, Aug 29, 2016 at 11:11:24AM -0700, Doug Anderson wrote:
> On rk3399 we explicitly set ppll in the device tree to 676000000.  The
> ppll has one major child, pclk_pmu_src, that is the parent of lots of
> other clocks.  Right now nobody is setting that clock rate and we're
> relying on the divider to just happen to be something sane.  Let's be
> explicit in our request so we're not relying on the firmware.
> 
> With the current firmware I tested with this patch has no expected
> impact but it's probably good to do anyway.
> 
> Signed-off-by: Douglas Anderson <dianders@...omium.org>
> ---
>  arch/arm64/boot/dts/rockchip/rk3399.dtsi | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/boot/dts/rockchip/rk3399.dtsi b/arch/arm64/boot/dts/rockchip/rk3399.dtsi
> index 62d450935a57..ffb3faa8c176 100644
> --- a/arch/arm64/boot/dts/rockchip/rk3399.dtsi
> +++ b/arch/arm64/boot/dts/rockchip/rk3399.dtsi
> @@ -908,8 +908,8 @@
>  		reg = <0x0 0xff750000 0x0 0x1000>;
>  		#clock-cells = <1>;
>  		#reset-cells = <1>;
> -		assigned-clocks = <&pmucru PLL_PPLL>;
> -		assigned-clock-rates = <676000000>;
> +		assigned-clocks = <&pmucru PLL_PPLL>, <&pmucru PCLK_SRC_PMU>;
> +		assigned-clock-rates = <676000000>, <112666667>;

I think this makes sense and is a good idea. One alternative would be to
have the various children actually set a rate that they expect, but
several of them don't have a separate driver at all, and that would be
of dubious value anyway I think.

Reviewed-by: Brian Norris <briannorris@...omium.org>

>  	};
>  
>  	cru: clock-controller@...60000 {
> -- 
> 2.8.0.rc3.226.g39d4020
>