linux-kernel - Re: [PATCH v1] riscv: dts: starfive: move timebase-frequency to .dtsi

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Message-ID: <f807bd04-02b9-4fda-97b9-7b47ce0cd87a@starfivetech.com>
Date:   Mon, 4 Dec 2023 19:29:35 +0800
From:   Xingyu Wu <xingyu.wu@...rfivetech.com>
To:     Conor Dooley <conor@...nel.org>,
        Emil Renner Berthing <kernel@...il.dk>,
        <linux-riscv@...ts.infradead.org>
CC:     Conor Dooley <conor.dooley@...rochip.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Walker Chen <walker.chen@...rfivetech.com>,
        JeeHeng Sia <jeeheng.sia@...rfivetech.com>,
        Leyfoon Tan <leyfoon.tan@...rfivetech.com>
Subject: Re: [PATCH v1] riscv: dts: starfive: move timebase-frequency to .dtsi

On 2023/12/1 0:11, Conor Dooley wrote:
> From: Conor Dooley <conor.dooley@...rochip.com>
> 
> Properties fixed by the SoC should be defined in the $soc.dtsi, and the
> timebase-frequency is not sourced directly from an off-chip oscillator.
> 
> Signed-off-by: Conor Dooley <conor.dooley@...rochip.com>
> ---
> I actually have no idea whether this is true or not, I asked on the
> jh8100 series but only got an answer for that SoC and not the existing
> ones. I'm hoping that a patch envokes more of a reaction!
> 
> CC: Emil Renner Berthing <kernel@...il.dk>
> CC: Conor Dooley <conor@...nel.org>
> CC: Rob Herring <robh+dt@...nel.org>
> CC: Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>
> CC: Paul Walmsley <paul.walmsley@...ive.com>
> CC: Palmer Dabbelt <palmer@...belt.com>
> CC: linux-riscv@...ts.infradead.org
> CC: devicetree@...r.kernel.org
> CC: linux-kernel@...r.kernel.org
> CC: Walker Chen <walker.chen@...rfivetech.com>
> CC: JeeHeng Sia <jeeheng.sia@...rfivetech.com>
> CC: Leyfoon Tan <leyfoon.tan@...rfivetech.com>
> ---
>  arch/riscv/boot/dts/starfive/jh7100-common.dtsi               | 4 ----
>  arch/riscv/boot/dts/starfive/jh7100.dtsi                      | 1 +
>  .../riscv/boot/dts/starfive/jh7110-starfive-visionfive-2.dtsi | 4 ----
>  arch/riscv/boot/dts/starfive/jh7110.dtsi                      | 1 +
>  4 files changed, 2 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/riscv/boot/dts/starfive/jh7100-common.dtsi b/arch/riscv/boot/dts/starfive/jh7100-common.dtsi
> index b93ce351a90f..214f27083d7b 100644
> --- a/arch/riscv/boot/dts/starfive/jh7100-common.dtsi
> +++ b/arch/riscv/boot/dts/starfive/jh7100-common.dtsi
> @@ -19,10 +19,6 @@ chosen {
>  		stdout-path = "serial0:115200n8";
>  	};
>  
> -	cpus {
> -		timebase-frequency = <6250000>;
> -	};
> -
>  	memory@...00000 {
>  		device_type = "memory";
>  		reg = <0x0 0x80000000 0x2 0x0>;
> diff --git a/arch/riscv/boot/dts/starfive/jh7100.dtsi b/arch/riscv/boot/dts/starfive/jh7100.dtsi
> index e68cafe7545f..c50b32424721 100644
> --- a/arch/riscv/boot/dts/starfive/jh7100.dtsi
> +++ b/arch/riscv/boot/dts/starfive/jh7100.dtsi
> @@ -16,6 +16,7 @@ / {
>  	cpus {
>  		#address-cells = <1>;
>  		#size-cells = <0>;
> +		timebase-frequency = <6250000>;
>  
>  		U74_0: cpu@0 {
>  			compatible = "sifive,u74-mc", "riscv";
> diff --git a/arch/riscv/boot/dts/starfive/jh7110-starfive-visionfive-2.dtsi b/arch/riscv/boot/dts/starfive/jh7110-starfive-visionfive-2.dtsi
> index b89e9791efa7..7873c7ffde4d 100644
> --- a/arch/riscv/boot/dts/starfive/jh7110-starfive-visionfive-2.dtsi
> +++ b/arch/riscv/boot/dts/starfive/jh7110-starfive-visionfive-2.dtsi
> @@ -26,10 +26,6 @@ chosen {
>  		stdout-path = "serial0:115200n8";
>  	};
>  
> -	cpus {
> -		timebase-frequency = <4000000>;
> -	};
> -
>  	memory@...00000 {
>  		device_type = "memory";
>  		reg = <0x0 0x40000000 0x1 0x0>;
> diff --git a/arch/riscv/boot/dts/starfive/jh7110.dtsi b/arch/riscv/boot/dts/starfive/jh7110.dtsi
> index 45213cdf50dc..ee7d4bb1f537 100644
> --- a/arch/riscv/boot/dts/starfive/jh7110.dtsi
> +++ b/arch/riscv/boot/dts/starfive/jh7110.dtsi
> @@ -18,6 +18,7 @@ / {
>  	cpus {
>  		#address-cells = <1>;
>  		#size-cells = <0>;
> +		timebase-frequency = <4000000>;
>  
>  		S7_0: cpu@0 {
>  			compatible = "sifive,s7", "riscv";


Hi Conor and Emil,

I found some information that I hope will be useful to you.
What Emil said is right:
osc (24MHz) -> rtc_toggle (div N) -> mtime

I found the N is depend on this clock register in drivers/clk/starfive/clk-starfive-jh7110-sys.c:

 83         JH71X0__DIV(JH7110_SYSCLK_RTC_TOGGLE, "rtc_toggle", 6, JH7110_SYSCLK_OSC),

and the description of the register is that the divider defaults to and is fixed to 6. So the timebase-frequency is 4MHz on the JH7110.

Best regards,
Xingyu Wu