Re: [PATCH] ACPI / LPIT: Register attributes based on FADT

Rafael J. Wysocki
2018-10-05T09:46:01Z

On Friday, September 28, 2018 10:54:02 AM CEST Rajneesh Bhardwaj wrote:
> ACPI Low Power S0 Idle capabilities are announced via FADT table and can
> be used to inform the kernel about the presence of one or more Low Power
> Idle (LPI) entries as descried in LPIT table. LPIT table can exist
> independently even if the FADT S0 Idle flag is not set and thus it could
> confuse user since the following cpuidle attributes are created.
>
> /sys/devices/system/cpu/cpuidle/low_power_idle_cpu_residency_us
> /sys/devices/system/cpu/cpuidle/low_power_idle_system_residency_us
>
> Presence or absence of above attributes could mean that the given
> platform supports S0ix state or not.
>
> This change allows to create the above cpuidle attributes only if
> FADT table supports Low Power S0 Idle.
>
> Cc: Rafael J . Wysocki <rafael.j.wysocki@intel.com>
> Cc: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
> Signed-off-by: Rajneesh Bhardwaj <rajneesh.bhardwaj@linux.intel.com>
> ---
> drivers/acpi/acpi_lpit.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/drivers/acpi/acpi_lpit.c b/drivers/acpi/acpi_lpit.c
> index cf4fc0161164..e43cb71b6972 100644
> --- a/drivers/acpi/acpi_lpit.c
> +++ b/drivers/acpi/acpi_lpit.c
> @@ -117,11 +117,17 @@ 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,
>

Applied, thanks!