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

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Message-ID: <CALHNRZ_9tMi5iihyTsEuU4T72=oTQM6-rVhqozzLf9DiB_TpcA@mail.gmail.com>
Date: Mon, 12 May 2025 23:26:41 -0500
From: Aaron Kling <webgeek1234@...il.com>
To: Jon Hunter <jonathanh@...dia.com>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>, Viresh Kumar <viresh.kumar@...aro.org>, 
	Thierry Reding <thierry.reding@...il.com>, 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 Fri, May 9, 2025 at 8:38 AM Jon Hunter <jonathanh@...dia.com> wrote:
>
>
>
> 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.

A hard dependency would likely make more sense here. I can update this
in a new revision. When I first set the soft dependency, I wasn't
certain how the driver worked, so I was trying to be less intrusive.

> > * 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?

These are separate things, aren't they? What's unregistered in the
remove is the cpufreq-dt device. And what's unregistered here is the
tegra124-cpufreq device. Not the same thing, unless I'm really missing
something.

Sincerely,
Aaron