linux-kernel - Re: [PATCH v4 2/2] cpufreq: tegra124: Allow building as a module

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Message-ID: <cd801698-d7cf-4e9e-aa01-5525f8687ab0@nvidia.com>
Date: Fri, 9 May 2025 14:37:54 +0100
From: Jon Hunter <jonathanh@...dia.com>
To: webgeek1234@...il.com, "Rafael J. Wysocki" <rafael@...nel.org>,
 Viresh Kumar <viresh.kumar@...aro.org>,
 Thierry Reding <thierry.reding@...il.com>
Cc: linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-tegra@...r.kernel.org
Subject: Re: [PATCH v4 2/2] cpufreq: tegra124: Allow building as a module



On 09/05/2025 01:04, Aaron Kling via B4 Relay wrote:
> From: Aaron Kling <webgeek1234@...il.com>
> 
> This requires three changes:
> * A soft dependency on cpufreq-dt as this driver only handles power
>    management and cpufreq-dt does the real operations

Hmmm .. how is this handled for other drivers using the cpufreq-dt 
driver? I see the imx driver has a dependency on this.

> * Adding a remove routine to remove the cpufreq-dt device
> * Adding a exit routine to handle cleaning up the driver
> 
> Signed-off-by: Aaron Kling <webgeek1234@...il.com>
> ---
>   drivers/cpufreq/Kconfig.arm        |  2 +-
>   drivers/cpufreq/tegra124-cpufreq.c | 36 ++++++++++++++++++++++++++++++++----
>   2 files changed, 33 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/cpufreq/Kconfig.arm b/drivers/cpufreq/Kconfig.arm
> index 4f9cb943d945c244eb2b29f543d14df6cac4e5d4..625f6fbdaaf5fd774e3b0bb996eb7ce980da41ee 100644
> --- a/drivers/cpufreq/Kconfig.arm
> +++ b/drivers/cpufreq/Kconfig.arm
> @@ -238,7 +238,7 @@ config ARM_TEGRA20_CPUFREQ
>   	  This adds the CPUFreq driver support for Tegra20/30 SOCs.
>   
>   config ARM_TEGRA124_CPUFREQ
> -	bool "Tegra124 CPUFreq support"
> +	tristate "Tegra124 CPUFreq support"
>   	depends on ARCH_TEGRA || COMPILE_TEST
>   	depends on CPUFREQ_DT
>   	default y
> diff --git a/drivers/cpufreq/tegra124-cpufreq.c b/drivers/cpufreq/tegra124-cpufreq.c
> index bc0691e8971f9454def37f489e4a3e244100b9f4..b6059c91f2474c56809c403eca94eacf51df734f 100644
> --- a/drivers/cpufreq/tegra124-cpufreq.c
> +++ b/drivers/cpufreq/tegra124-cpufreq.c
> @@ -16,6 +16,8 @@
>   #include <linux/pm_opp.h>
>   #include <linux/types.h>
>   
> +static struct platform_device *platform_device;

Do we need this?

> +
>   struct tegra124_cpufreq_priv {
>   	struct clk *cpu_clk;
>   	struct clk *pllp_clk;
> @@ -176,6 +178,21 @@ static int __maybe_unused tegra124_cpufreq_resume(struct device *dev)
>   	return err;
>   }
>   
> +static void tegra124_cpufreq_remove(struct platform_device *pdev)
> +{
> +	struct tegra124_cpufreq_priv *priv = dev_get_drvdata(&pdev->dev);
> +
> +	if (!IS_ERR(priv->cpufreq_dt_pdev)) {
> +		platform_device_unregister(priv->cpufreq_dt_pdev);
> +		priv->cpufreq_dt_pdev = ERR_PTR(-ENODEV);
> +	}
> +
> +	clk_put(priv->pllp_clk);
> +	clk_put(priv->pllx_clk);
> +	clk_put(priv->dfll_clk);
> +	clk_put(priv->cpu_clk);
> +}
> +
>   static const struct dev_pm_ops tegra124_cpufreq_pm_ops = {
>   	SET_SYSTEM_SLEEP_PM_OPS(tegra124_cpufreq_suspend,
>   				tegra124_cpufreq_resume)
> @@ -185,12 +202,12 @@ static struct platform_driver tegra124_cpufreq_platdrv = {
>   	.driver.name	= "cpufreq-tegra124",
>   	.driver.pm	= &tegra124_cpufreq_pm_ops,
>   	.probe		= tegra124_cpufreq_probe,
> +	.remove		= tegra124_cpufreq_remove,
>   };
>   
>   static int __init tegra_cpufreq_init(void)
>   {
>   	int ret;
> -	struct platform_device *pdev;
>   
>   	if (!(of_machine_is_compatible("nvidia,tegra124") ||
>   		of_machine_is_compatible("nvidia,tegra210")))
> @@ -204,15 +221,26 @@ static int __init tegra_cpufreq_init(void)
>   	if (ret)
>   		return ret;
>   
> -	pdev = platform_device_register_simple("cpufreq-tegra124", -1, NULL, 0);
> -	if (IS_ERR(pdev)) {
> +	platform_device = platform_device_register_simple("cpufreq-tegra124", -1, NULL, 0);
> +	if (IS_ERR(platform_device)) {
>   		platform_driver_unregister(&tegra124_cpufreq_platdrv);
> -		return PTR_ERR(pdev);
> +		return PTR_ERR(platform_device);
>   	}
>   
>   	return 0;
>   }
>   module_init(tegra_cpufreq_init);
>   
> +static void __exit tegra_cpufreq_module_exit(void)
> +{
> +	if (platform_device && !IS_ERR(platform_device))
> +		platform_device_unregister(platform_device);

The device is unregistered in the remove. Why do we need this?

> +
> +	platform_driver_unregister(&tegra124_cpufreq_platdrv);
> +}
> +module_exit(tegra_cpufreq_module_exit);
> +
> +MODULE_SOFTDEP("pre: cpufreq-dt");
>   MODULE_AUTHOR("Tuomas Tynkkynen <ttynkkynen@...dia.com>");
>   MODULE_DESCRIPTION("cpufreq driver for NVIDIA Tegra124");
> +MODULE_LICENSE("GPL");
> 

-- 
nvpublic