include/reset.h

   1 /*
   2  * Copyright (c) 2016, NVIDIA CORPORATION.
   3  *
   4  * SPDX-License-Identifier: GPL-2.0
   5  */
   6
   7 #ifndef _RESET_H
   8 #define _RESET_H
   9
  10 #include <linux/errno.h>
  11
  12 /**
  13  * A reset is a hardware signal indicating that a HW module (or IP block, or
  14  * sometimes an entire off-CPU chip) reset all of its internal state to some
  15  * known-good initial state. Drivers will often reset HW modules when they
  16  * begin execution to ensure that hardware correctly responds to all requests,
  17  * or in response to some error condition. Reset signals are often controlled
  18  * externally to the HW module being reset, by an entity this API calls a reset
  19  * controller. This API provides a standard means for drivers to request that
  20  * reset controllers set or clear reset signals.
  21  *
  22  * A driver that implements UCLASS_RESET is a reset controller or provider. A
  23  * controller will often implement multiple separate reset signals, since the
  24  * hardware it manages often has this capability. reset-uclass.h describes the
  25  * interface which reset controllers must implement.
  26  *
  27  * Reset consumers/clients are the HW modules affected by reset signals. This
  28  * header file describes the API used by drivers for those HW modules.
  29  */
  30
  31 struct udevice;
  32
  33 /**
  34  * struct reset_ctl - A handle to (allowing control of) a single reset signal.
  35  *
  36  * Clients provide storage for reset control handles. The content of the
  37  * structure is managed solely by the reset API and reset drivers. A reset
  38  * control struct is initialized by "get"ing the reset control struct. The
  39  * reset control struct is passed to all other reset APIs to identify which
  40  * reset signal to operate upon.
  41  *
  42  * @dev: The device which implements the reset signal.
  43  * @id: The reset signal ID within the provider.
  44  *
  45  * Currently, the reset API assumes that a single integer ID is enough to
  46  * identify and configure any reset signal for any reset provider. If this
  47  * assumption becomes invalid in the future, the struct could be expanded to
  48  * either (a) add more fields to allow reset providers to store additional
  49  * information, or (b) replace the id field with an opaque pointer, which the
  50  * provider would dynamically allocated during its .of_xlate op, and process
  51  * during is .request op. This may require the addition of an extra op to clean
  52  * up the allocation.
  53  */
  54 struct reset_ctl {
  55         struct udevice *dev;
  56         /*
  57          * Written by of_xlate. We assume a single id is enough for now. In the
  58          * future, we might add more fields here.
  59          */
  60         unsigned long id;
  61 };
  62
  63 #ifdef CONFIG_DM_RESET
  64 /**
  65  * reset_get_by_index - Get/request a reset signal by integer index.
  66  *
  67  * This looks up and requests a reset signal. The index is relative to the
  68  * client device; each device is assumed to have n reset signals associated
  69  * with it somehow, and this function finds and requests one of them. The
  70  * mapping of client device reset signal indices to provider reset signals may
  71  * be via device-tree properties, board-provided mapping tables, or some other
  72  * mechanism.
  73  *
  74  * @dev:        The client device.
  75  * @index:      The index of the reset signal to request, within the client's
  76  *              list of reset signals.
  77  * @reset_ctl   A pointer to a reset control struct to initialize.
  78  * @return 0 if OK, or a negative error code.
  79  */
  80 int reset_get_by_index(struct udevice *dev, int index,
  81                        struct reset_ctl *reset_ctl);
  82
  83 /**
  84  * reset_get_by_name - Get/request a reset signal by name.
  85  *
  86  * This looks up and requests a reset signal. The name is relative to the
  87  * client device; each device is assumed to have n reset signals associated
  88  * with it somehow, and this function finds and requests one of them. The
  89  * mapping of client device reset signal names to provider reset signal may be
  90  * via device-tree properties, board-provided mapping tables, or some other
  91  * mechanism.
  92  *
  93  * @dev:        The client device.
  94  * @name:       The name of the reset signal to request, within the client's
  95  *              list of reset signals.
  96  * @reset_ctl:  A pointer to a reset control struct to initialize.
  97  * @return 0 if OK, or a negative error code.
  98  */
  99 int reset_get_by_name(struct udevice *dev, const char *name,
 100                       struct reset_ctl *reset_ctl);
 101
 102 /**
 103  * reset_request - Request a reset signal.
 104  *
 105  * @reset_ctl:  A reset control struct.
 106  *
 107  * @return 0 if OK, or a negative error code.
 108  */
 109 int reset_request(struct reset_ctl *reset_ctl);
 110
 111 /**
 112  * reset_free - Free a previously requested reset signal.
 113  *
 114  * @reset_ctl:  A reset control struct that was previously successfully
 115  *              requested by reset_get_by_*().
 116  * @return 0 if OK, or a negative error code.
 117  */
 118 int reset_free(struct reset_ctl *reset_ctl);
 119
 120 /**
 121  * reset_assert - Assert a reset signal.
 122  *
 123  * This function will assert the specified reset signal, thus resetting the
 124  * affected HW module(s). Depending on the reset controller hardware, the reset
 125  * signal will either stay asserted until reset_deassert() is called, or the
 126  * hardware may autonomously clear the reset signal itself.
 127  *
 128  * @reset_ctl:  A reset control struct that was previously successfully
 129  *              requested by reset_get_by_*().
 130  * @return 0 if OK, or a negative error code.
 131  */
 132 int reset_assert(struct reset_ctl *reset_ctl);
 133
 134 /**
 135  * reset_deassert - Deassert a reset signal.
 136  *
 137  * This function will deassert the specified reset signal, thus releasing the
 138  * affected HW modules() from reset, and allowing them to continue normal
 139  * operation.
 140  *
 141  * @reset_ctl:  A reset control struct that was previously successfully
 142  *              requested by reset_get_by_*().
 143  * @return 0 if OK, or a negative error code.
 144  */
 145 int reset_deassert(struct reset_ctl *reset_ctl);
 146
 147 /**
 148  * reset_release_all - Assert/Free an array of previously requested resets.
 149  *
 150  * For each reset contained in the reset array, this function will check if
 151  * reset has been previously requested and then will assert and free it.
 152  *
 153  * @reset_ctl:  A reset struct array that was previously successfully
 154  *              requested by reset_get_by_*().
 155  * @count       Number of reset contained in the array
 156  * @return 0 if OK, or a negative error code.
 157  */
 158 int reset_release_all(struct reset_ctl *reset_ctl, int count);
 159 #else
 160 static inline int reset_get_by_index(struct udevice *dev, int index,
 161                                      struct reset_ctl *reset_ctl)
 162 {
 163         return -ENOTSUPP;
 164 }
 165
 166 static inline int reset_get_by_name(struct udevice *dev, const char *name,
 167                                     struct reset_ctl *reset_ctl)
 168 {
 169         return -ENOTSUPP;
 170 }
 171
 172 static inline int reset_free(struct reset_ctl *reset_ctl)
 173 {
 174         return 0;
 175 }
 176
 177 static inline int reset_assert(struct reset_ctl *reset_ctl)
 178 {
 179         return 0;
 180 }
 181
 182 static inline int reset_deassert(struct reset_ctl *reset_ctl)
 183 {
 184         return 0;
 185 }
 186
 187 static inline int reset_release_all(struct reset_ctl *reset_ctl, int count)
 188 {
 189         return 0;
 190 }
 191
 192 #endif
 193
 194 #endif