RE: [PATCH] Revert "ACPI / PM: LPIT: Register sysfs attributes based on FADT"

[Limonciello, Mario]

[Public]



> -----Original Message-----
> From: Rafael J. Wysocki <rjw@xxxxxxxxxxxxx>
> Sent: Wednesday, July 13, 2022 12:33
> To: Linux ACPI <linux-acpi@xxxxxxxxxxxxxxx>
> Cc: LKML <linux-kernel@xxxxxxxxxxxxxxx>; Linux PM <linux-
> pm@xxxxxxxxxxxxxxx>; Srinivas Pandruvada
> <srinivas.pandruvada@xxxxxxxxxxxxxxx>; Zhang Rui <rui.zhang@xxxxxxxxx>;
> Limonciello, Mario <Mario.Limonciello@xxxxxxx>
> Subject: [PATCH] Revert "ACPI / PM: LPIT: Register sysfs attributes based on
> FADT"
> 
> Author: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> 
> Revert commit 1cdda9486f51 ("ACPI / PM: LPIT: Register sysfs attributes
> based on FADT"), because what it did was more confusing than it would
> be to allow the sysfs attributes in question to be created regardless
> of whether or not the relevant flag was set in the FADT.
> 
> If ACPI_FADT_LOW_POWER_S0 is not set, it need not mean that LPIT is
> invalid and low-power S0 idle is not usable.  It merely means that
> using S3 on the given system is more beneficial from the energy
> saving perspective than using low-power S0 idle.
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>

Reviewed-by: Mario Limonciello <mario.limonciello@xxxxxxx>

> ---
> diff --git a/drivers/acpi/acpi_lpit.c b/drivers/acpi/acpi_lpit.c
> index 48e5059d67ca..50540d4d4948 100644
> --- a/drivers/acpi/acpi_lpit.c
> +++ b/drivers/acpi/acpi_lpit.c
> @@ -109,17 +109,11 @@ static void lpit_update_residency(struct
> lpit_residency_info *info,
>  		if (!info->iomem_addr)
>  			return;
> 
> -		if (!(acpi_gbl_FADT.flags & ACPI_FADT_LOW_POWER_S0))
> -			return;
> -
>  		/* Silently fail, if cpuidle attribute group is not present */
>  		sysfs_add_file_to_group(&cpu_subsys.dev_root->kobj,
> 
> 	&dev_attr_low_power_idle_system_residency_us.attr,
>  					"cpuidle");
>  	} else if (info->gaddr.space_id ==
> ACPI_ADR_SPACE_FIXED_HARDWARE) {
> -		if (!(acpi_gbl_FADT.flags & ACPI_FADT_LOW_POWER_S0))
> -			return;
> -
>  		/* Silently fail, if cpuidle attribute group is not present */
>  		sysfs_add_file_to_group(&cpu_subsys.dev_root->kobj,
> 
> 	&dev_attr_low_power_idle_cpu_residency_us.attr,
> 
>