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/*
* Copyright (c) 2016, NVIDIA CORPORATION.
*
* SPDX-License-Identifier: GPL-2.0
*/
#ifndef _RESET_H
#define _RESET_H
#include <linux/errno.h>
/**
* A reset is a hardware signal indicating that a HW module (or IP block, or
* sometimes an entire off-CPU chip) reset all of its internal state to some
* known-good initial state. Drivers will often reset HW modules when they
* begin execution to ensure that hardware correctly responds to all requests,
* or in response to some error condition. Reset signals are often controlled
* externally to the HW module being reset, by an entity this API calls a reset
* controller. This API provides a standard means for drivers to request that
* reset controllers set or clear reset signals.
*
* A driver that implements UCLASS_RESET is a reset controller or provider. A
* controller will often implement multiple separate reset signals, since the
* hardware it manages often has this capability. reset-uclass.h describes the
* interface which reset controllers must implement.
*
* Reset consumers/clients are the HW modules affected by reset signals. This
* header file describes the API used by drivers for those HW modules.
*/
struct udevice;
/**
* struct reset_ctl - A handle to (allowing control of) a single reset signal.
*
* Clients provide storage for reset control handles. The content of the
* structure is managed solely by the reset API and reset drivers. A reset
* control struct is initialized by "get"ing the reset control struct. The
* reset control struct is passed to all other reset APIs to identify which
* reset signal to operate upon.
*
* @dev: The device which implements the reset signal.
* @id: The reset signal ID within the provider.
*
* Currently, the reset API assumes that a single integer ID is enough to
* identify and configure any reset signal for any reset provider. If this
* assumption becomes invalid in the future, the struct could be expanded to
* either (a) add more fields to allow reset providers to store additional
* information, or (b) replace the id field with an opaque pointer, which the
* provider would dynamically allocated 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 reset_ctl {
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;
};
#ifdef CONFIG_DM_RESET
/**
* reset_get_by_index - Get/request a reset signal by integer index.
*
* This looks up and requests a reset signal. The index is relative to the
* client device; each device is assumed to have n reset signals associated
* with it somehow, and this function finds and requests one of them. The
* mapping of client device reset signal indices to provider reset signals may
* be via device-tree properties, board-provided mapping tables, or some other
* mechanism.
*
* @dev: The client device.
* @index: The index of the reset signal to request, within the client's
* list of reset signals.
* @reset_ctl A pointer to a reset control struct to initialize.
* @return 0 if OK, or a negative error code.
*/
int reset_get_by_index(struct udevice *dev, int index,
struct reset_ctl *reset_ctl);
/**
* reset_get_by_name - Get/request a reset signal by name.
*
* This looks up and requests a reset signal. The name is relative to the
* client device; each device is assumed to have n reset signals associated
* with it somehow, and this function finds and requests one of them. The
* mapping of client device reset signal names to provider reset signal may be
* via device-tree properties, board-provided mapping tables, or some other
* mechanism.
*
* @dev: The client device.
* @name: The name of the reset signal to request, within the client's
* list of reset signals.
* @reset_ctl: A pointer to a reset control struct to initialize.
* @return 0 if OK, or a negative error code.
*/
int reset_get_by_name(struct udevice *dev, const char *name,
struct reset_ctl *reset_ctl);
/**
* reset_free - Free a previously requested reset signal.
*
* @reset_ctl: A reset control struct that was previously successfully
* requested by reset_get_by_*().
* @return 0 if OK, or a negative error code.
*/
int reset_free(struct reset_ctl *reset_ctl);
/**
* reset_assert - Assert a reset signal.
*
* This function will assert the specified reset signal, thus resetting the
* affected HW module(s). Depending on the reset controller hardware, the reset
* signal will either stay asserted until reset_deassert() is called, or the
* hardware may autonomously clear the reset signal itself.
*
* @reset_ctl: A reset control struct that was previously successfully
* requested by reset_get_by_*().
* @return 0 if OK, or a negative error code.
*/
int reset_assert(struct reset_ctl *reset_ctl);
/**
* reset_deassert - Deassert a reset signal.
*
* This function will deassert the specified reset signal, thus releasing the
* affected HW modules() from reset, and allowing them to continue normal
* operation.
*
* @reset_ctl: A reset control struct that was previously successfully
* requested by reset_get_by_*().
* @return 0 if OK, or a negative error code.
*/
int reset_deassert(struct reset_ctl *reset_ctl);
#else
static inline int reset_get_by_index(struct udevice *dev, int index,
struct reset_ctl *reset_ctl)
{
return -ENOTSUPP;
}
static inline int reset_get_by_name(struct udevice *dev, const char *name,
struct reset_ctl *reset_ctl)
{
return -ENOTSUPP;
}
static inline int reset_free(struct reset_ctl *reset_ctl)
{
return 0;
}
static inline int reset_assert(struct reset_ctl *reset_ctl)
{
return 0;
}
static inline int reset_deassert(struct reset_ctl *reset_ctl)
{
return 0;
}
#endif
#endif
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