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Darwin Rambo989ce042014-02-11 11:06:34 -08001/*
2 * Copyright 2013 Broadcom Corporation.
3 *
4 * SPDX-License-Identifier: GPL-2.0+
5 */
6
7/*
8 * Bitfield operations
9 *
10 * These are generic bitfield operations which allow manipulation of variable
11 * width bitfields within a word. One use of this would be to use data tables
12 * to determine how to reprogram fields within R/W hardware registers.
13 *
14 * Example:
15 *
16 * old_reg_val
17 * +--------+----+---+--+-----+----------+
18 * | | | | | old | |
19 * +--------+----+---+--+-----+----------+
20 *
21 * new_reg_val
22 * +--------+----+---+--+-----+----------+
23 * | | | | | new | |
24 * +--------+----+---+--+-----+----------+
25 *
26 * mask = bitfield_mask(10, 5);
27 * old = bitfield_extract(old_reg_val, 10, 5);
28 * new_reg_val = bitfield_replace(old_reg_val, 10, 5, new);
29 *
Codrin Ciubotariu8756de22015-07-24 16:55:25 +030030 * or
31 *
32 * mask = bitfield_mask(10, 5);
33 * old = bitfield_extract_by_mask(old_reg_val, mask);
34 * new_reg_val = bitfield_replace_by_mask(old_reg_val, mask, new);
35 *
Darwin Rambo989ce042014-02-11 11:06:34 -080036 * The numbers 10 and 5 could for example come from data
37 * tables which describe all bitfields in all registers.
38 */
39
40#include <linux/types.h>
41
42/* Produces a mask of set bits covering a range of a uint value */
43static inline uint bitfield_mask(uint shift, uint width)
44{
45 return ((1 << width) - 1) << shift;
46}
47
48/* Extract the value of a bitfield found within a given register value */
49static inline uint bitfield_extract(uint reg_val, uint shift, uint width)
50{
51 return (reg_val & bitfield_mask(shift, width)) >> shift;
52}
53
54/*
55 * Replace the value of a bitfield found within a given register value
56 * Returns the newly modified uint value with the replaced field.
57 */
58static inline uint bitfield_replace(uint reg_val, uint shift, uint width,
59 uint bitfield_val)
60{
61 uint mask = bitfield_mask(shift, width);
62
Codrin Ciubotariuc69abd82015-07-24 16:52:19 +030063 return (reg_val & ~mask) | ((bitfield_val << shift) & mask);
Darwin Rambo989ce042014-02-11 11:06:34 -080064}
Codrin Ciubotariu8756de22015-07-24 16:55:25 +030065
66/* Produces a shift of the bitfield given a mask */
67static inline uint bitfield_shift(uint mask)
68{
69 return mask ? ffs(mask) - 1 : 0;
70}
71
72/* Extract the value of a bitfield found within a given register value */
73static inline uint bitfield_extract_by_mask(uint reg_val, uint mask)
74{
75 uint shift = bitfield_shift(mask);
76
77 return (reg_val & mask) >> shift;
78}
79
80/*
81 * Replace the value of a bitfield found within a given register value
82 * Returns the newly modified uint value with the replaced field.
83 */
84static inline uint bitfield_replace_by_mask(uint reg_val, uint mask,
85 uint bitfield_val)
86{
87 uint shift = bitfield_shift(mask);
88
89 return (reg_val & ~mask) | ((bitfield_val << shift) & mask);
90}