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

Limonciello, Mario
2022-07-13T18:09:53Z

[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,
>
>