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

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

[Rafael J. Wysocki]

Author: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

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@intel.com>
---
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,

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

[Limonciello, Mario]

[Public]



> -----Original Message-----
> From: Rafael J. Wysocki <rjw@rjwysocki.net>
> Sent: Wednesday, July 13, 2022 12:33
> To: Linux ACPI <linux-acpi@vger.kernel.org>
> Cc: LKML <linux-kernel@vger.kernel.org>; Linux PM <linux-
> pm@vger.kernel.org>; Srinivas Pandruvada
> <srinivas.pandruvada@linux.intel.com>; Zhang Rui <rui.zhang@intel.com>;
> Limonciello, Mario <Mario.Limonciello@amd.com>
> Subject: [PATCH] Revert "ACPI / PM: LPIT: Register sysfs attributes based on
> FADT"
> 
> Author: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> 
> 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@intel.com>

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

> ---
> 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,
> 
>