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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   */
scom_init(const struct scom_controller * controller)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   */
scom_map_ok(scom_map_t map)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  
scom_map(struct device_node * ctrl_dev,u64 reg,u64 count)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   */
scom_unmap(scom_map_t map)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   */
scom_read(scom_map_t map,u64 reg,u64 * value)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   */
scom_write(scom_map_t map,u64 reg,u64 value)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 */
168