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4815db87f5
My motivation for this patch is to make reset control handling optional for generic drivers. I want to add reset control to drivers/usb/host/ehci-generic.c, but it is used by several platforms, some will implement a reset controller driver, some will not. Add no-op stubs in order to avoid link error for drivers that implement reset controlling, but still it is optional. Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
167 lines
5.8 KiB
C
167 lines
5.8 KiB
C
/*
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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 _RESET_H
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#define _RESET_H
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#include <linux/errno.h>
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/**
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* A reset is a hardware signal indicating that a HW module (or IP block, or
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* sometimes an entire off-CPU chip) reset all of its internal state to some
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* known-good initial state. Drivers will often reset HW modules when they
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* begin execution to ensure that hardware correctly responds to all requests,
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* or in response to some error condition. Reset signals are often controlled
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* externally to the HW module being reset, by an entity this API calls a reset
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* controller. This API provides a standard means for drivers to request that
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* reset controllers set or clear reset signals.
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*
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* A driver that implements UCLASS_RESET is a reset controller or provider. A
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* controller will often implement multiple separate reset signals, since the
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* hardware it manages often has this capability. reset-uclass.h describes the
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* interface which reset controllers must implement.
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*
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* Reset consumers/clients are the HW modules affected by reset signals. This
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* header file describes the API used by drivers for those HW modules.
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*/
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struct udevice;
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/**
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* struct reset_ctl - A handle to (allowing control of) a single reset signal.
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*
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* Clients provide storage for reset control handles. The content of the
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* structure is managed solely by the reset API and reset drivers. A reset
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* control struct is initialized by "get"ing the reset control struct. The
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* reset control struct is passed to all other reset APIs to identify which
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* reset signal to operate upon.
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*
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* @dev: The device which implements the reset signal.
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* @id: The reset signal ID within the provider.
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*
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* Currently, the reset API assumes that a single integer ID is enough to
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* identify and configure any reset signal for any reset provider. If this
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* assumption becomes invalid in the future, the struct could be expanded to
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* either (a) add more fields to allow reset providers to store additional
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* information, or (b) replace the id field with an opaque pointer, which the
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* provider would dynamically allocated during its .of_xlate op, and process
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* during is .request op. This may require the addition of an extra op to clean
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* up the allocation.
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*/
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struct reset_ctl {
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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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#ifdef CONFIG_DM_RESET
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/**
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* reset_get_by_index - Get/request a reset signal by integer index.
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*
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* This looks up and requests a reset signal. The index is relative to the
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* client device; each device is assumed to have n reset signals associated
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* with it somehow, and this function finds and requests one of them. The
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* mapping of client device reset signal indices to provider reset signals may
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* be via device-tree properties, board-provided mapping tables, or some other
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* mechanism.
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*
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* @dev: The client device.
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* @index: The index of the reset signal to request, within the client's
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* list of reset signals.
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* @reset_ctl A pointer to a reset control 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 reset_get_by_index(struct udevice *dev, int index,
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struct reset_ctl *reset_ctl);
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/**
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* reset_get_by_name - Get/request a reset signal by name.
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*
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* This looks up and requests a reset signal. The name is relative to the
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* client device; each device is assumed to have n reset signals associated
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* with it somehow, and this function finds and requests one of them. The
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* mapping of client device reset signal names to provider reset signal may be
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* via device-tree properties, board-provided mapping tables, or some other
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* mechanism.
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*
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* @dev: The client device.
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* @name: The name of the reset signal to request, within the client's
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* list of reset signals.
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* @reset_ctl: A pointer to a reset control 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 reset_get_by_name(struct udevice *dev, const char *name,
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struct reset_ctl *reset_ctl);
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/**
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* reset_free - Free a previously requested reset signal.
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*
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* @reset_ctl: A reset control struct that was previously successfully
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* requested by reset_get_by_*().
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* @return 0 if OK, or a negative error code.
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*/
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int reset_free(struct reset_ctl *reset_ctl);
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/**
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* reset_assert - Assert a reset signal.
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*
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* This function will assert the specified reset signal, thus resetting the
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* affected HW module(s). Depending on the reset controller hardware, the reset
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* signal will either stay asserted until reset_deassert() is called, or the
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* hardware may autonomously clear the reset signal itself.
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*
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* @reset_ctl: A reset control struct that was previously successfully
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* requested by reset_get_by_*().
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* @return 0 if OK, or a negative error code.
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*/
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int reset_assert(struct reset_ctl *reset_ctl);
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/**
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* reset_deassert - Deassert a reset signal.
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*
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* This function will deassert the specified reset signal, thus releasing the
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* affected HW modules() from reset, and allowing them to continue normal
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* operation.
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*
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* @reset_ctl: A reset control struct that was previously successfully
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* requested by reset_get_by_*().
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* @return 0 if OK, or a negative error code.
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*/
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int reset_deassert(struct reset_ctl *reset_ctl);
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#else
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static inline int reset_get_by_index(struct udevice *dev, int index,
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struct reset_ctl *reset_ctl)
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{
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return -ENOTSUPP;
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}
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static inline int reset_get_by_name(struct udevice *dev, const char *name,
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struct reset_ctl *reset_ctl)
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{
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return -ENOTSUPP;
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}
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static inline int reset_free(struct reset_ctl *reset_ctl)
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{
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return 0;
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}
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static inline int reset_assert(struct reset_ctl *reset_ctl)
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{
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return 0;
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}
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static inline int reset_deassert(struct reset_ctl *reset_ctl)
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{
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return 0;
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}
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#endif
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#endif
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