Commit eeb2d80d authored by Srinivas Pandruvada's avatar Srinivas Pandruvada Committed by Rafael J. Wysocki
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ACPI / LPIT: Add Low Power Idle Table (LPIT) support 

Add functionality to read LPIT table, which provides:

 - Sysfs interface to read residency counters via
   /sys/devices/system/cpu/cpuidle/low_power_idle_cpu_residency_us
   /sys/devices/system/cpu/cpuidle/low_power_idle_system_residency_us

Here the count "low_power_idle_cpu_residency_us" shows the time spent
by CPU package in low power state.  This is read via MSR interface,
which points to MSR for PKG C10.

Here the count "low_power_idle_system_residency_us" show the count the
system was in low power state. This is read via MMIO interface. This
is mapped to SLP_S0 residency on modern Intel systems. This residency
is achieved only when CPU is in PKG C10 and all functional blocks are
in low power state.

It is possible that none of the above counters present or anyone of the
counter present or all counters present.

For example: On my Kabylake system both of the above counters present.
After suspend to idle these counts updated and prints:

 6916179
 6998564

This counter can be read by tools like turbostat to display. Or it can
be used to debug, if modern systems are reaching desired low power state.

 - Provides an interface to read residency counter memory address

   This address can be used to get the base address of PMC memory
   mapped IO.  This is utilized by intel_pmc_core driver to print
   more debug information.

In addition, to avoid code duplication to read iomem, removed the read of
iomem from acpi_os_read_memory() in osl.c and made a common function
acpi_os_read_iomem(). This new function is used for reading iomem in
in both osl.c and acpi_lpit.c.

Link: http://www.uefi.org/sites/default/files/resources/Intel_ACPI_Low_Power_S0_Idle.pdf


Signed-off-by: default avatarSrinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent c2ebf788

Documentation/acpi/lpit.txt

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To enumerate platform Low Power Idle states, Intel platforms are using

“Low Power Idle Table” (LPIT). More details about this table can be

downloaded from:

http://www.uefi.org/sites/default/files/resources/Intel_ACPI_Low_Power_S0_Idle.pdf



Residencies for each low power state can be read via FFH

(Function fixed hardware) or a memory mapped interface.



On platforms supporting S0ix sleep states, there can be two types of

residencies:

- CPU PKG C10 (Read via FFH interface)

- Platform Controller Hub (PCH) SLP_S0 (Read via memory mapped interface)



The following attributes are added dynamically to the cpuidle

sysfs attribute group:

	/sys/devices/system/cpu/cpuidle/low_power_idle_cpu_residency_us

	/sys/devices/system/cpu/cpuidle/low_power_idle_system_residency_us



The "low_power_idle_cpu_residency_us" attribute shows time spent

by the CPU package in PKG C10



The "low_power_idle_system_residency_us" attribute shows SLP_S0

residency, or system time spent with the SLP_S0# signal asserted.

This is the lowest possible system power state, achieved only when CPU is in

PKG C10 and all functional blocks in PCH are in a low power state.

drivers/acpi/Kconfig

+5 −0
Original line number Diff line number Diff line
@@ -80,6 +80,11 @@ endif 
config ACPI_SPCR_TABLE

	bool



config ACPI_LPIT

	bool

	depends on X86_64

	default y



config ACPI_SLEEP

	bool

	depends on SUSPEND || HIBERNATION

drivers/acpi/Makefile

+1 −0
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@@ -56,6 +56,7 @@ acpi-$(CONFIG_DEBUG_FS) += debugfs.o 
acpi-$(CONFIG_ACPI_NUMA)	+= numa.o

acpi-$(CONFIG_ACPI_PROCFS_POWER) += cm_sbs.o

acpi-y				+= acpi_lpat.o

acpi-$(CONFIG_ACPI_LPIT)	+= acpi_lpit.o

acpi-$(CONFIG_ACPI_GENERIC_GSI) += irq.o

acpi-$(CONFIG_ACPI_WATCHDOG)	+= acpi_watchdog.o

drivers/acpi/acpi_lpit.c

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/*

 * acpi_lpit.c - LPIT table processing functions

 *

 * Copyright (C) 2017 Intel Corporation. All rights reserved.

 *

 * This program is free software; you can redistribute it and/or

 * modify it under the terms of the GNU General Public License version

 * 2 as published by the Free Software Foundation.

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 */



#include <linux/cpu.h>

#include <linux/acpi.h>

#include <asm/msr.h>

#include <asm/tsc.h>



struct lpit_residency_info {

	struct acpi_generic_address gaddr;

	u64 frequency;

	void __iomem *iomem_addr;

};



/* Storage for an memory mapped and FFH based entries */

static struct lpit_residency_info residency_info_mem;

static struct lpit_residency_info residency_info_ffh;



static int lpit_read_residency_counter_us(u64 *counter, bool io_mem)

{

	int err;



	if (io_mem) {

		u64 count = 0;

		int error;



		error = acpi_os_read_iomem(residency_info_mem.iomem_addr, &count,

					   residency_info_mem.gaddr.bit_width);

		if (error)

			return error;



		*counter = div64_u64(count * 1000000ULL, residency_info_mem.frequency);

		return 0;

	}



	err = rdmsrl_safe(residency_info_ffh.gaddr.address, counter);

	if (!err) {

		u64 mask = GENMASK_ULL(residency_info_ffh.gaddr.bit_offset +

				       residency_info_ffh.gaddr. bit_width - 1,

				       residency_info_ffh.gaddr.bit_offset);



		*counter &= mask;

		*counter >>= residency_info_ffh.gaddr.bit_offset;

		*counter = div64_u64(*counter * 1000000ULL, residency_info_ffh.frequency);

		return 0;

	}



	return -ENODATA;

}



static ssize_t low_power_idle_system_residency_us_show(struct device *dev,

						       struct device_attribute *attr,

						       char *buf)

{

	u64 counter;

	int ret;



	ret = lpit_read_residency_counter_us(&counter, true);

	if (ret)

		return ret;



	return sprintf(buf, "%llu\n", counter);

}

static DEVICE_ATTR_RO(low_power_idle_system_residency_us);



static ssize_t low_power_idle_cpu_residency_us_show(struct device *dev,

						    struct device_attribute *attr,

						    char *buf)

{

	u64 counter;

	int ret;



	ret = lpit_read_residency_counter_us(&counter, false);

	if (ret)

		return ret;



	return sprintf(buf, "%llu\n", counter);

}

static DEVICE_ATTR_RO(low_power_idle_cpu_residency_us);



int lpit_read_residency_count_address(u64 *address)

{

	if (!residency_info_mem.gaddr.address)

		return -EINVAL;



	*address = residency_info_mem.gaddr.address;



	return 0;

}



static void lpit_update_residency(struct lpit_residency_info *info,

				 struct acpi_lpit_native *lpit_native)

{

	info->frequency = lpit_native->counter_frequency ?

				lpit_native->counter_frequency : tsc_khz * 1000;

	if (!info->frequency)

		info->frequency = 1;



	info->gaddr = lpit_native->residency_counter;

	if (info->gaddr.space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY) {

		info->iomem_addr = ioremap_nocache(info->gaddr.address,

						   info->gaddr.bit_width / 8);

		if (!info->iomem_addr)

			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) {

		/* 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,

					"cpuidle");

	}

}



static void lpit_process(u64 begin, u64 end)

{

	while (begin + sizeof(struct acpi_lpit_native) < end) {

		struct acpi_lpit_native *lpit_native = (struct acpi_lpit_native *)begin;



		if (!lpit_native->header.type && !lpit_native->header.flags) {

			if (lpit_native->residency_counter.space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY &&

			    !residency_info_mem.gaddr.address) {

				lpit_update_residency(&residency_info_mem, lpit_native);

			} else if (lpit_native->residency_counter.space_id == ACPI_ADR_SPACE_FIXED_HARDWARE &&

				   !residency_info_ffh.gaddr.address) {

				lpit_update_residency(&residency_info_ffh, lpit_native);

			}

		}

		begin += lpit_native->header.length;

	}

}



void acpi_init_lpit(void)

{

	acpi_status status;

	u64 lpit_begin;

	struct acpi_table_lpit *lpit;



	status = acpi_get_table(ACPI_SIG_LPIT, 0, (struct acpi_table_header **)&lpit);



	if (ACPI_FAILURE(status))

		return;



	lpit_begin = (u64)lpit + sizeof(*lpit);

	lpit_process(lpit_begin, lpit_begin + lpit->header.length);

}

drivers/acpi/internal.h

+6 −0
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@@ -248,4 +248,10 @@ void acpi_watchdog_init(void); 
static inline void acpi_watchdog_init(void) {}

#endif



#ifdef CONFIG_ACPI_LPIT

void acpi_init_lpit(void);

#else

static inline void acpi_init_lpit(void) { }

#endif



#endif /* _ACPI_INTERNAL_H_ */

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