LXR linux/arch/powerpc/include/asm/scom.h

   1/*
   2 * Copyright 2010 Benjamin Herrenschmidt, IBM Corp
   3 *                <benh@kernel.crashing.org>
   4 *     and        David Gibson, IBM Corporation.
   5 *
   6 *   This program is free software;  you can redistribute it and/or modify
   7 *   it under the terms of the GNU General Public License as published by
   8 *   the Free Software Foundation; either version 2 of the License, or
   9 *   (at your option) any later version.
  10 *
  11 *   This program is distributed in the hope that it will be useful,
  12 *   but WITHOUT ANY WARRANTY;  without even the implied warranty of
  13 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
  14 *   the GNU General Public License for more details.
  15 *
  16 *   You should have received a copy of the GNU General Public License
  17 *   along with this program;  if not, write to the Free Software
  18 *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  19 */
  20
  21#ifndef _ASM_POWERPC_SCOM_H
  22#define _ASM_POWERPC_SCOM_H
  23
  24#ifdef __KERNEL__
  25#ifndef __ASSEMBLY__
  26#ifdef CONFIG_PPC_SCOM
  27
  28/*
  29 * The SCOM bus is a sideband bus used for accessing various internal
  30 * registers of the processor or the chipset. The implementation details
  31 * differ between processors and platforms, and the access method as
  32 * well.
  33 *
  34 * This API allows to "map" ranges of SCOM register numbers associated
  35 * with a given SCOM controller. The later must be represented by a
  36 * device node, though some implementations might support NULL if there
  37 * is no possible ambiguity
  38 *
  39 * Then, scom_read/scom_write can be used to accesses registers inside
  40 * that range. The argument passed is a register number relative to
  41 * the beginning of the range mapped.
  42 */
  43
  44typedef void *scom_map_t;
  45
  46/* Value for an invalid SCOM map */
  47#define SCOM_MAP_INVALID        (NULL)
  48
  49/* The scom_controller data structure is what the platform passes
  50 * to the core code in scom_init, it provides the actual implementation
  51 * of all the SCOM functions
  52 */
  53struct scom_controller {
  54        scom_map_t (*map)(struct device_node *ctrl_dev, u64 reg, u64 count);
  55        void (*unmap)(scom_map_t map);
  56
  57        int (*read)(scom_map_t map, u64 reg, u64 *value);
  58        int (*write)(scom_map_t map, u64 reg, u64 value);
  59};
  60
  61extern const struct scom_controller *scom_controller;
  62
  63/**
  64 * scom_init - Initialize the SCOM backend, called by the platform
  65 * @controller: The platform SCOM controller
  66 */
  67static inline void scom_init(const struct scom_controller *controller)
  68{
  69        scom_controller = controller;
  70}
  71
  72/**
  73 * scom_map_ok - Test is a SCOM mapping is successful
  74 * @map: The result of scom_map to test
  75 */
  76static inline int scom_map_ok(scom_map_t map)
  77{
  78        return map != SCOM_MAP_INVALID;
  79}
  80
  81/**
  82 * scom_map - Map a block of SCOM registers
  83 * @ctrl_dev: Device node of the SCOM controller
  84 *            some implementations allow NULL here
  85 * @reg: first SCOM register to map
  86 * @count: Number of SCOM registers to map
  87 */
  88
  89static inline scom_map_t scom_map(struct device_node *ctrl_dev,
  90                                  u64 reg, u64 count)
  91{
  92        return scom_controller->map(ctrl_dev, reg, count);
  93}
  94
  95/**
  96 * scom_find_parent - Find the SCOM controller for a device
  97 * @dev: OF node of the device
  98 *
  99 * This is not meant for general usage, but in combination with
 100 * scom_map() allows to map registers not represented by the
 101 * device own scom-reg property. Useful for applying HW workarounds
 102 * on things not properly represented in the device-tree for example.
 103 */
 104struct device_node *scom_find_parent(struct device_node *dev);
 105
 106
 107/**
 108 * scom_map_device - Map a device's block of SCOM registers
 109 * @dev: OF node of the device
 110 * @index: Register bank index (index in "scom-reg" property)
 111 *
 112 * This function will use the device-tree binding for SCOM which
 113 * is to follow "scom-parent" properties until it finds a node with
 114 * a "scom-controller" property to find the controller. It will then
 115 * use the "scom-reg" property which is made of reg/count pairs,
 116 * each of them having a size defined by the controller's #scom-cells
 117 * property
 118 */
 119extern scom_map_t scom_map_device(struct device_node *dev, int index);
 120
 121
 122/**
 123 * scom_unmap - Unmap a block of SCOM registers
 124 * @map: Result of scom_map is to be unmapped
 125 */
 126static inline void scom_unmap(scom_map_t map)
 127{
 128        if (scom_map_ok(map))
 129                scom_controller->unmap(map);
 130}
 131
 132/**
 133 * scom_read - Read a SCOM register
 134 * @map: Result of scom_map
 135 * @reg: Register index within that map
 136 * @value: Updated with the value read
 137 *
 138 * Returns 0 (success) or a negative error code
 139 */
 140static inline int scom_read(scom_map_t map, u64 reg, u64 *value)
 141{
 142        int rc;
 143
 144        rc = scom_controller->read(map, reg, value);
 145        if (rc)
 146                *value = 0xfffffffffffffffful;
 147        return rc;
 148}
 149
 150/**
 151 * scom_write - Write to a SCOM register
 152 * @map: Result of scom_map
 153 * @reg: Register index within that map
 154 * @value: Value to write
 155 *
 156 * Returns 0 (success) or a negative error code
 157 */
 158static inline int scom_write(scom_map_t map, u64 reg, u64 value)
 159{
 160        return scom_controller->write(map, reg, value);
 161}
 162
 163
 164#endif /* CONFIG_PPC_SCOM */
 165#endif /* __ASSEMBLY__ */
 166#endif /* __KERNEL__ */
 167#endif /* _ASM_POWERPC_SCOM_H */
 168