power-domain.h
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/* SPDX-License-Identifier: GPL-2.0 */
/*
* Copyright (c) 2016, NVIDIA CORPORATION.
*/
#ifndef _POWER_DOMAIN_H
#define _POWER_DOMAIN_H
/**
* A power domain is a portion of an SoC or chip that is powered by a
* switchable source of power. In many cases, software has control over the
* power domain, and can turn the power source on or off. This is typically
* done to save power by powering off unused devices, or to enable software
* sequencing of initial powerup at boot. This API provides a means for
* drivers to turn power domains on and off.
*
* A driver that implements UCLASS_POWER_DOMAIN is a power domain controller or
* provider. A controller will often implement multiple separate power domains,
* since the hardware it manages often has this capability.
* power-domain-uclass.h describes the interface which power domain controllers
* must implement.
*
* Depending on the power domain controller hardware, changing the state of a
* power domain may require performing related operations on other resources.
* For example, some power domains may require certain clocks to be enabled
* whenever the power domain is powered on, or during the time when the power
* domain is transitioning state. These details are implementation-specific
* and should ideally be encapsulated entirely within the provider driver, or
* configured through mechanisms (e.g. device tree) that do not require client
* drivers to provide extra configuration information.
*
* Power domain consumers/clients are the drivers for HW modules within the
* power domain. This header file describes the API used by those drivers.
*
* In many cases, a single complex IO controller (e.g. a PCIe controller) will
* be the sole logic contained within a power domain. In such cases, it is
* logical for the relevant device driver to directly control that power
* domain. In other cases, multiple controllers, each with their own driver,
* may be contained in a single power domain. Any logic require to co-ordinate
* between drivers for these multiple controllers is beyond the scope of this
* API at present. Equally, this API does not define or implement any policy
* by which power domains are managed.
*/
struct udevice;
/**
* struct power_domain - A handle to (allowing control of) a single power domain.
*
* Clients provide storage for power domain handles. The content of the
* structure is managed solely by the power domain API and power domain
* drivers. A power domain struct is initialized by "get"ing the power domain
* struct. The power domain struct is passed to all other power domain APIs to
* identify which power domain to operate upon.
*
* @dev: The device which implements the power domain.
* @id: The power domain ID within the provider.
*
* Currently, the power domain API assumes that a single integer ID is enough
* to identify and configure any power domain for any power domain provider. If
* this assumption becomes invalid in the future, the struct could be expanded
* to either (a) add more fields to allow power domain providers to store
* additional information, or (b) replace the id field with an opaque pointer,
* which the provider would dynamically allocate during its .of_xlate op, and
* process during is .request op. This may require the addition of an extra op
* to clean up the allocation.
*/
struct power_domain {
struct udevice *dev;
/*
* Written by of_xlate. We assume a single id is enough for now. In the
* future, we might add more fields here.
*/
unsigned long id;
};
/**
* power_domain_get - Get/request the power domain for a device.
*
* This looks up and requests a power domain. Each device is assumed to have
* a single (or, at least one) power domain associated with it somehow, and
* that domain, or the first/default domain. The mapping of client device to
* provider power domain may be via device-tree properties, board-provided
* mapping tables, or some other mechanism.
*
* @dev: The client device.
* @power_domain A pointer to a power domain struct to initialize.
* @return 0 if OK, or a negative error code.
*/
#if CONFIG_IS_ENABLED(POWER_DOMAIN)
int power_domain_get(struct udevice *dev, struct power_domain *power_domain);
#else
static inline
int power_domain_get(struct udevice *dev, struct power_domain *power_domain)
{
return -ENOSYS;
}
#endif
/**
* power_domain_get_by_index - Get the indexed power domain for a device.
*
* @dev: The client device.
* @power_domain: A pointer to a power domain struct to initialize.
* @index: Power domain index to be powered on.
*
* @return 0 if OK, or a negative error code.
*/
#if CONFIG_IS_ENABLED(POWER_DOMAIN)
int power_domain_get_by_index(struct udevice *dev,
struct power_domain *power_domain, int index);
#else
static inline
int power_domain_get_by_index(struct udevice *dev,
struct power_domain *power_domain, int index)
{
return -ENOSYS;
}
#endif
/**
* power_domain_free - Free a previously requested power domain.
*
* @power_domain: A power domain struct that was previously successfully
* requested by power_domain_get().
* @return 0 if OK, or a negative error code.
*/
#if CONFIG_IS_ENABLED(POWER_DOMAIN)
int power_domain_free(struct power_domain *power_domain);
#else
static inline int power_domain_free(struct power_domain *power_domain)
{
return -ENOSYS;
}
#endif
/**
* power_domain_on - Enable power to a power domain.
*
* @power_domain: A power domain struct that was previously successfully
* requested by power_domain_get().
* @return 0 if OK, or a negative error code.
*/
#if CONFIG_IS_ENABLED(POWER_DOMAIN)
int power_domain_on(struct power_domain *power_domain);
#else
static inline int power_domain_on(struct power_domain *power_domain)
{
return -ENOSYS;
}
#endif
/**
* power_domain_off - Disable power to a power domain.
*
* @power_domain: A power domain struct that was previously successfully
* requested by power_domain_get().
* @return 0 if OK, or a negative error code.
*/
#if CONFIG_IS_ENABLED(POWER_DOMAIN)
int power_domain_off(struct power_domain *power_domain);
#else
static inline int power_domain_off(struct power_domain *power_domain)
{
return -ENOSYS;
}
#endif
#endif