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