path: root/drivers/acpi/device_pm.c

/*
 * drivers/acpi/device_pm.c - ACPI device power management routines.
 *
 * Copyright (C) 2012, Intel Corp.
 * Author: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
 *
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 *
 *  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.
 *
 *  You should have received a copy of the GNU General Public License along
 *  with this program; if not, write to the Free Software Foundation, Inc.,
 *  59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
 *
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 */

#include <linux/device.h>
#include <linux/export.h>
#include <linux/mutex.h>
#include <linux/pm_qos.h>
#include <linux/pm_runtime.h>

#include <acpi/acpi.h>
#include <acpi/acpi_bus.h>
#include <acpi/acpi_drivers.h>

#include "internal.h"

#define _COMPONENT	ACPI_POWER_COMPONENT
ACPI_MODULE_NAME("device_pm");

/**
 * acpi_power_state_string - String representation of ACPI device power state.
 * @state: ACPI device power state to return the string representation of.
 */
const char *acpi_power_state_string(int state)
{
	switch (state) {
	case ACPI_STATE_D0:
		return "D0";
	case ACPI_STATE_D1:
		return "D1";
	case ACPI_STATE_D2:
		return "D2";
	case ACPI_STATE_D3_HOT:
		return "D3hot";
	case ACPI_STATE_D3_COLD:
		return "D3cold";
	default:
		return "(unknown)";
	}
}

/**
 * acpi_device_get_power - Get power state of an ACPI device.
 * @device: Device to get the power state of.
 * @state: Place to store the power state of the device.
 *
 * This function does not update the device's power.state field, but it may
 * update its parent's power.state field (when the parent's power state is
 * unknown and the device's power state turns out to be D0).
 */
int acpi_device_get_power(struct acpi_device *device, int *state)
{
	int result = ACPI_STATE_UNKNOWN;

	if (!device || !state)
		return -EINVAL;

	if (!device->flags.power_manageable) {
		/* TBD: Non-recursive algorithm for walking up hierarchy. */
		*state = device->parent ?
			device->parent->power.state : ACPI_STATE_D0;
		goto out;
	}

	/*
	 * Get the device's power state from power resources settings and _PSC,
	 * if available.
	 */
	if (device->power.flags.power_resources) {
		int error = acpi_power_get_inferred_state(device, &result);
		if (error)
			return error;
	}
	if (device->power.flags.explicit_get) {
		acpi_handle handle = device->handle;
		unsigned long long psc;
		acpi_status status;

		status = acpi_evaluate_integer(handle, "_PSC", NULL, &psc);
		if (ACPI_FAILURE(status))
			return -ENODEV;

		/*
		 * The power resources settings may indicate a power state
		 * shallower than the actual power state of the device.
		 *
		 * Moreover, on systems predating ACPI 4.0, if the device
		 * doesn't depend on any power resources and _PSC returns 3,
		 * that means "power off".  We need to maintain compatibility
		 * with those systems.
		 */
		if (psc > result && psc < ACPI_STATE_D3_COLD)
			result = psc;
		else if (result == ACPI_STATE_UNKNOWN)
			result = psc > ACPI_STATE_D2 ? ACPI_STATE_D3_COLD : psc;
	}

	/*
	 * If we were unsure about the device parent's power state up to this
	 * point, the fact that the device is in D0 implies that the parent has
	 * to be in D0 too.
	 */
	if (device->parent && device->parent->power.state == ACPI_STATE_UNKNOWN
	    && result == ACPI_STATE_D0)
		device->parent->power.state = ACPI_STATE_D0;

	*state = result;

 out:
	ACPI_DEBUG_PRINT((ACPI_DB_INFO, "Device [%s] power state is %s\n",
			  device->pnp.bus_id, acpi_power_state_string(*state)));

	return 0;
}

static int acpi_dev_pm_explicit_set(struct acpi_device *adev, int state)
{
	if (adev->power.states[state].flags.explicit_set) {
		char method[5] = { '_', 'P', 'S', '0' + state, '\0' };
		acpi_status status;

		status = acpi_evaluate_object(adev->handle, method, NULL, NULL);
		if (ACPI_FAILURE(status))
			return -ENODEV;
	}
	return 0;
}

/**
 * acpi_device_set_power - Set power state of an ACPI device.
 * @device: Device to set the power state of.
 * @state: New power state to set.
 *
 * Callers must ensure that the device is power manageable before using this
 * function.
 */
int acpi_device_set_power(struct acpi_device *device, int state)
{
	int result = 0;
	bool cut_power = false;

	if (!device || (state < ACPI_STATE_D0) || (state > ACPI_STATE_D3_COLD))
		return -EINVAL;

	/* Make sure this is a valid target state */

	if (state == device->power.state) {
		ACPI_DEBUG_PRINT((ACPI_DB_INFO, "Device is already at %s