linux-kernel - Re: [PATCH v3] clk: starfive: pll: Fix lower rate of CPUfreq by setting PLL0 rate to 1.5GHz

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Message-ID: <8d21b1bc-9402-41d4-bd81-c521c8a33d2d@kernel.org>
Date: Tue, 2 Apr 2024 18:18:09 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
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 v3] clk: starfive: pll: Fix lower rate of CPUfreq by
 setting PLL0 rate to 1.5GHz

On 02/04/2024 11:09, 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.
> 
> So PLL0 rate should be default set to 1.5GHz. But setting the
> PLL0 rate need certain steps:
> 
> 1. Change the parent of cpu_root clock to OSC clock.
> 2. Change the divider of cpu_core if PLL0 rate is higher than
>    1.25GHz before CPUfreq boot.
> 3. Change the parent of cpu_root clock back to PLL0 clock.
> 
> Reviewed-by: Hal Feng <hal.feng@...rfivetech.com>
> Fixes: e2c510d6d630 ("riscv: dts: starfive: Add cpu scaling for JH7110 SoC")
> Signed-off-by: Xingyu Wu <xingyu.wu@...rfivetech.com>
> ---
> 
> Hi Stephen and Emil,
> 
> This patch fixes the issue about lower rate of CPUfreq[1] by setting PLL0
> rate to 1.5GHz.
> 
> In order not to affect the cpu operation, setting the PLL0 rate need
> certain steps. The cpu_root's parent clock should be changed first. And
> the divider of the cpu_core clock should be set to 2 so they won't crash
> when setting 1.5GHz without voltage regulation. Due to PLL driver boot
> earlier than SYSCRG driver, cpu_core and cpu_root clocks are using by
> ioremap(). 
> 
> [1]: https://github.com/starfive-tech/VisionFive2/issues/55
> 
> Previous patch link:
> v2: https://lore.kernel.org/all/20230821152915.208366-1-xingyu.wu@starfivetech.com/
> v1: https://lore.kernel.org/all/20230811033631.160912-1-xingyu.wu@starfivetech.com/
> 
> Thanks,
> Xingyu Wu
> ---
>  .../jh7110-starfive-visionfive-2.dtsi         |   5 +
>  .../clk/starfive/clk-starfive-jh7110-pll.c    | 102 ++++++++++++++++++

Please do not mix DTS and driver code. That's not really portable. DTS
is being exported and used in other projects.

..

>  
> @@ -458,6 +535,8 @@ static int jh7110_pll_probe(struct platform_device *pdev)
>  	struct jh7110_pll_priv *priv;
>  	unsigned int idx;
>  	int ret;
> +	struct device_node *np;
> +	struct resource res;
>  
>  	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
>  	if (!priv)
> @@ -489,6 +568,29 @@ static int jh7110_pll_probe(struct platform_device *pdev)
>  			return ret;
>  	}
>  
> +	priv->is_first_set = true;
> +	np = of_find_compatible_node(NULL, NULL, "starfive,jh7110-syscrg");

Your drivers should not do it. It's fragile, hides true link/dependency.
Please use phandles.


> +	if (!np) {
> +		ret = PTR_ERR(np);
> +		dev_err(priv->dev, "failed to get syscrg node\n");
> +		goto np_put;
> +	}
> +
> +	ret = of_address_to_resource(np, 0, &res);
> +	if (ret) {
> +		dev_err(priv->dev, "failed to get syscrg resource\n");
> +		goto np_put;
> +	}
> +
> +	priv->syscrg_base = ioremap(res.start, resource_size(&res));
> +	if (!priv->syscrg_base)
> +		ret = -ENOMEM;

Why are you mapping other device's IO? How are you going to ensure
synced access to registers?



Best regards,
Krzysztof