linux-kernel - Re: [PATCH 3/5] ARC: AXS103: DTS: Add core pll node to manage cpu frequency

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Date:   Tue, 22 Aug 2017 13:40:50 -0700
From:   Vineet Gupta <Vineet.Gupta1@...opsys.com>
To:     Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>,
        "linux-snps-arc@...ts.infradead.org" 
        <linux-snps-arc@...ts.infradead.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Alexey Brodkin" <Alexey.Brodkin@...opsys.com>,
        Rob Herring <robh+dt@...nel.org>,
        "Mark Rutland" <mark.rutland@....com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH 3/5] ARC: AXS103: DTS: Add core pll node to manage cpu
 frequency

On 08/14/2017 09:12 AM, Eugeniy Paltsev wrote:
> Add core pll node (core_clk) to manage cpu frequency.
> core_clk represents pll itself.
> input_clk represents clock signal source (basically xtal) which
> comes to pll input.
>
> Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>
> ---
>   arch/arc/boot/dts/axc003.dtsi     | 11 +++++++++--
>   arch/arc/boot/dts/axc003_idu.dtsi | 11 +++++++++--
>   2 files changed, 18 insertions(+), 4 deletions(-)
>
> diff --git a/arch/arc/boot/dts/axc003.dtsi b/arch/arc/boot/dts/axc003.dtsi
> index cc9239e..dca7e39 100644
> --- a/arch/arc/boot/dts/axc003.dtsi
> +++ b/arch/arc/boot/dts/axc003.dtsi
> @@ -24,10 +24,17 @@
>   
>   		ranges = <0x00000000 0x0 0xf0000000 0x10000000>;
>   
> -		core_clk: core_clk {
> +		input_clk: input-clk {
>   			#clock-cells = <0>;
>   			compatible = "fixed-clock";
> -			clock-frequency = <90000000>;
> +			clock-frequency = <33333333>;

Note our custom built UP bitfiles for AXS generally can do 90 MHz only - you are 
likely breaking linux on them now by forcing 100 MHz ?

> +		};
> +
> +		core_clk: core-clk@80 {
> +			compatible = "snps,axs10x-arc-pll-clock";
> +			reg = <0x80 0x10>, <0x100 0x10>;
> +			#clock-cells = <0>;
> +			clocks = <&input_clk>;
>   		};
>   
>   		core_intc: archs-intc@cpu {
> diff --git a/arch/arc/boot/dts/axc003_idu.dtsi b/arch/arc/boot/dts/axc003_idu.dtsi
> index 4ebb2170..5b56bef 100644
> --- a/arch/arc/boot/dts/axc003_idu.dtsi
> +++ b/arch/arc/boot/dts/axc003_idu.dtsi
> @@ -24,10 +24,17 @@
>   
>   		ranges = <0x00000000 0x0 0xf0000000 0x10000000>;
>   
> -		core_clk: core_clk {
> +		input_clk: input-clk {
>   			#clock-cells = <0>;
>   			compatible = "fixed-clock";
> -			clock-frequency = <100000000>;
> +			clock-frequency = <33333333>;
> +		};
> +
> +		core_clk: core-clk@80 {
> +			compatible = "snps,axs10x-arc-pll-clock";
> +			reg = <0x80 0x10>, <0x100 0x10>;
> +			#clock-cells = <0>;
> +			clocks = <&input_clk>;
>   		};
>   
>   		core_intc: archs-intc@cpu {