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
  44 typedef 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  */
  53 struct 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
  61 extern 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  */
  67 static 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  */
  76 static 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
  89 static 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  */
 104 struct 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  */
 119 extern 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  */
 126 static 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  */
 140 static 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  */
 158 static 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 */