linux-kernel - [PATCH 4.19 080/361] ACPI / PM: LPIT: Register sysfs attributes based on FADT

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Date:   Sun, 11 Nov 2018 14:17:07 -0800
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Rajneesh Bhardwaj <rajneesh.bhardwaj@...ux.intel.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 080/361] ACPI / PM: LPIT: Register sysfs attributes based on FADT

4.19-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Rajneesh Bhardwaj <rajneesh.bhardwaj@...ux.intel.com>

[ Upstream commit 1cdda9486f5103fb133f88e662e48c504adbb779 ]

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.

Signed-off-by: Rajneesh Bhardwaj <rajneesh.bhardwaj@...ux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/acpi/acpi_lpit.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/drivers/acpi/acpi_lpit.c
+++ b/drivers/acpi/acpi_lpit.c
@@ -117,11 +117,17 @@ static void lpit_update_residency(struct
 		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,