linux-kernel - Re: [PATCH v5 2/2] riscv: dts: starfive: visionfive-2: Fix lower rate of CPUfreq by setting PLL0 rate to 1.5GHz

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Date: Sat, 11 May 2024 13:47:08 -0500
From: Samuel Holland <samuel.holland@...ive.com>
To: Xingyu Wu <xingyu.wu@...rfivetech.com>,
 Michael Turquette <mturquette@...libre.com>, Stephen Boyd
 <sboyd@...nel.org>, Conor Dooley <conor@...nel.org>,
 Emil Renner Berthing <emil.renner.berthing@...onical.com>,
 Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>
Cc: Paul Walmsley <paul.walmsley@...ive.com>,
 Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>,
 Hal Feng <hal.feng@...rfivetech.com>, linux-kernel@...r.kernel.org,
 linux-clk@...r.kernel.org, linux-riscv@...ts.infradead.org,
 devicetree@...r.kernel.org
Subject: Re: [PATCH v5 2/2] riscv: dts: starfive: visionfive-2: Fix lower rate
 of CPUfreq by setting PLL0 rate to 1.5GHz

On 2024-05-07 1:53 AM, Xingyu Wu wrote:
> CPUfreq supports 4 cpu frequency loads on 375/500/750/1500MHz.
> But now PLL0 rate is 1GHz and the cpu frequency loads become
> 333/500/500/1000MHz in fact.
> 
> The PLL0 rate should be default set to 1.5GHz and set the
> cpu_core rate to 500MHz in safe.

Can this be accomplished by instead setting the CLK_SET_RATE_PARENT flag on the
CPU_CORE clock? That way PLL0 is automatically set when cpufreq tries to change
the CPU core frequency. Then there is no DT change and no compatibility issue.

Regards,
Samuel

> Fixes: e2c510d6d630 ("riscv: dts: starfive: Add cpu scaling for JH7110 SoC")
> Signed-off-by: Xingyu Wu <xingyu.wu@...rfivetech.com>
> ---
>  .../boot/dts/starfive/jh7110-starfive-visionfive-2.dtsi     | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> 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 45b58b6f3df8..28981b267de4 100644
> --- a/arch/riscv/boot/dts/starfive/jh7110-starfive-visionfive-2.dtsi
> +++ b/arch/riscv/boot/dts/starfive/jh7110-starfive-visionfive-2.dtsi
> @@ -390,6 +390,12 @@ spi_dev0: spi@0 {
>  	};
>  };
>  
> +&syscrg {
> +	assigned-clocks = <&syscrg JH7110_SYSCLK_CPU_CORE>,
> +			  <&pllclk JH7110_PLLCLK_PLL0_OUT>;
> +	assigned-clock-rates = <500000000>, <1500000000>;
> +};
> +
>  &sysgpio {
>  	i2c0_pins: i2c0-0 {
>  		i2c-pins {