linux-kernel - Re: [PATCH v1] ACPI: Split out processor thermal register from ACPI PSS

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Message-ID: <87h74ui0fq.fsf@stealth>
Date:   Thu, 09 Jun 2022 11:41:13 +0100
From:   Punit Agrawal <punit.agrawal@...edance.com>
To:     Riwen Lu <luriwen@...mail.com>
Cc:     rafael@...nel.org, lenb@...nel.org, robert.moore@...el.com,
        linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
        devel@...ica.org, Riwen Lu <luriwen@...inos.com>
Subject: Re: [PATCH v1] ACPI: Split out processor thermal register from ACPI
 PSS

Hi Riwen,

Riwen Lu <luriwen@...mail.com> writes:

> From: Riwen Lu <luriwen@...inos.com>
>
> In prior commit 239708a3af44 ("ACPI: Split out ACPI PSS from ACPI Processor
> driver"), move processor thermal register to acpi_pss_perf_init(), and it
> won't excute if ACPI_CPU_FREQ_PSS not enabled.
>
> Since ARM64 support P states by CPPC, it should also support processor
> passive cooling. So split out the processor thermal cooling register from
> ACPI PSS.

The commit log is a bit difficult to understand - maybe reword as -

    Commit 239708a3af44 ("ACPI: Split out ACPI PSS from ACPI Processor
    driver"), moves processor thermal registration to acpi_pss_perf_init(),
    which doesn't get executed if ACPI_CPU_FREQ_PSS is not enabled.

    As ARM64 supports P-states using CPPC, it should be possible to also
    support processor passive cooling even if PSS is not enabled. Split
    out the processor thermal cooling register from ACPI PSS to support
    this.

> Signed-off-by: Riwen Lu <luriwen@...inos.com>
> ---

[...]

> diff --git a/drivers/acpi/processor_driver.c b/drivers/acpi/processor_driver.c
> index 368a9edefd0c..c84738a24eca 100644
> --- a/drivers/acpi/processor_driver.c
> +++ b/drivers/acpi/processor_driver.c
> @@ -142,8 +142,6 @@ static int acpi_soft_cpu_dead(unsigned int cpu)
>  static int acpi_pss_perf_init(struct acpi_processor *pr,
>  		struct acpi_device *device)
>  {
> -	int result = 0;
> -
>  	acpi_processor_ppc_has_changed(pr, 0);
>  
>  	acpi_processor_get_throttling_info(pr);
> @@ -151,53 +149,7 @@ static int acpi_pss_perf_init(struct acpi_processor *pr,
>  	if (pr->flags.throttling)
>  		pr->flags.limit = 1;
>  
> -	pr->cdev = thermal_cooling_device_register("Processor", device,
> -						   &processor_cooling_ops);
> -	if (IS_ERR(pr->cdev)) {
> -		result = PTR_ERR(pr->cdev);
> -		return result;
> -	}
> -
> -	dev_dbg(&device->dev, "registered as cooling_device%d\n",
> -		pr->cdev->id);
> -
> -	result = sysfs_create_link(&device->dev.kobj,
> -				   &pr->cdev->device.kobj,
> -				   "thermal_cooling");
> -	if (result) {
> -		dev_err(&device->dev,
> -			"Failed to create sysfs link 'thermal_cooling'\n");
> -		goto err_thermal_unregister;
> -	}
> -
> -	result = sysfs_create_link(&pr->cdev->device.kobj,
> -				   &device->dev.kobj,
> -				   "device");
> -	if (result) {
> -		dev_err(&pr->cdev->device,
> -			"Failed to create sysfs link 'device'\n");
> -		goto err_remove_sysfs_thermal;
> -	}
> -
>  	return 0;
> -
> - err_remove_sysfs_thermal:
> -	sysfs_remove_link(&device->dev.kobj, "thermal_cooling");
> - err_thermal_unregister:
> -	thermal_cooling_device_unregister(pr->cdev);
> -
> -	return result;
> -}
> -
> -static void acpi_pss_perf_exit(struct acpi_processor *pr,
> -		struct acpi_device *device)
> -{
> -	if (pr->cdev) {
> -		sysfs_remove_link(&device->dev.kobj, "thermal_cooling");
> -		sysfs_remove_link(&pr->cdev->device.kobj, "device");
> -		thermal_cooling_device_unregister(pr->cdev);
> -		pr->cdev = NULL;
> -	}
>  }
>  #else
>  static inline int acpi_pss_perf_init(struct acpi_processor *pr,
> @@ -205,9 +157,6 @@ static inline int acpi_pss_perf_init(struct acpi_processor *pr,
>  {
>  	return 0;
>  }
> -
> -static inline void acpi_pss_perf_exit(struct acpi_processor *pr,
> -		struct acpi_device *device) {}
>  #endif /* CONFIG_ACPI_CPU_FREQ_PSS */
>  
>  static int __acpi_processor_start(struct acpi_device *device)
> @@ -229,9 +178,35 @@ static int __acpi_processor_start(struct acpi_device *device)
>  	if (!cpuidle_get_driver() || cpuidle_get_driver() == &acpi_idle_driver)
>  		acpi_processor_power_init(pr);
>  
> -	result = acpi_pss_perf_init(pr, device);
> -	if (result)
> +	acpi_pss_perf_init(pr, device);

The return value of acpi_pss_perf_init() isn't used anymore. Please also
update the function signature to void and drop the redundant return.

> +
> +	pr->cdev = thermal_cooling_device_register("Processor", device,
> +						   &processor_cooling_ops);
> +	if (IS_ERR(pr->cdev)) {
> +		result = PTR_ERR(pr->cdev);
>  		goto err_power_exit;
> +	}
> +
> +	dev_dbg(&device->dev, "registered as cooling_device%d\n",
> +		pr->cdev->id);
> +
> +	result = sysfs_create_link(&device->dev.kobj,
> +				   &pr->cdev->device.kobj,
> +				   "thermal_cooling");
> +	if (result) {
> +		dev_err(&device->dev,
> +			"Failed to create sysfs link 'thermal_cooling'\n");
> +		goto err_thermal_unregister;
> +	}
> +
> +	result = sysfs_create_link(&pr->cdev->device.kobj,
>> +				   &device->dev.kobj,
> +				   "device");
> +	if (result) {
> +		dev_err(&pr->cdev->device,
> +			"Failed to create sysfs link 'device'\n");
> +		goto err_remove_sysfs_thermal;
> +	}

Instead of copying the block back here, it would be better to move it
into a separate function in processor_thermal.c that can be called
here.

>  
>  	status = acpi_install_notify_handler(device->handle, ACPI_DEVICE_NOTIFY,
>  					     acpi_processor_notify, device);
> @@ -239,8 +214,11 @@ static int __acpi_processor_start(struct acpi_device *device)
>  		return 0;
>  
>  	result = -ENODEV;
> -	acpi_pss_perf_exit(pr, device);
> -
> +	sysfs_remove_link(&pr->cdev->device.kobj, "device");
> +err_remove_sysfs_thermal:
> +	sysfs_remove_link(&device->dev.kobj, "thermal_cooling");
> +err_thermal_unregister:
> +	thermal_cooling_device_unregister(pr->cdev);
>  err_power_exit:
>  	acpi_processor_power_exit(pr);
>  	return result;
> @@ -277,10 +255,15 @@ static int acpi_processor_stop(struct device *dev)
>  		return 0;
>  	acpi_processor_power_exit(pr);
>  
> -	acpi_pss_perf_exit(pr, device);
> -
>  	acpi_cppc_processor_exit(pr);
>  
> +	if (pr->cdev) {
> +		sysfs_remove_link(&device->dev.kobj, "thermal_cooling");
> +		sysfs_remove_link(&pr->cdev->device.kobj, "device");
> +		thermal_cooling_device_unregister(pr->cdev);
> +		pr->cdev = NULL;
> +	}
> +

Similarly, the removal can also be moved to a function in processor_thermal.c.

Thoughts?

[...]