1 /* SPDX-License-Identifier: GPL-2.0+ */
2 /*
3 * Copyright 2013 Broadcom Corporation.
4 */
5
6 /*
7 * Bitfield operations
8 *
9 * These are generic bitfield operations which allow manipulation of variable
10 * width bitfields within a word. One use of this would be to use data tables
11 * to determine how to reprogram fields within R/W hardware registers.
12 *
13 * Example:
14 *
15 * old_reg_val
16 * +--------+----+---+--+-----+----------+
17 * | | | | | old | |
18 * +--------+----+---+--+-----+----------+
19 *
20 * new_reg_val
21 * +--------+----+---+--+-----+----------+
22 * | | | | | new | |
23 * +--------+----+---+--+-----+----------+
24 *
25 * mask = bitfield_mask(10, 5);
26 * old = bitfield_extract(old_reg_val, 10, 5);
27 * new_reg_val = bitfield_replace(old_reg_val, 10, 5, new);
28 *
29 * or
30 *
31 * mask = bitfield_mask(10, 5);
32 * old = bitfield_extract_by_mask(old_reg_val, mask);
33 * new_reg_val = bitfield_replace_by_mask(old_reg_val, mask, new);
34 *
35 * The numbers 10 and 5 could for example come from data
36 * tables which describe all bitfields in all registers.
37 */
38
39 #include <linux/bitops.h>
40 #include <linux/types.h>
41
42 /* Produces a mask of set bits covering a range of a uint value */
bitfield_mask(uint shift,uint width)43 static 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 */
bitfield_extract(uint reg_val,uint shift,uint width)49 static 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 */
bitfield_replace(uint reg_val,uint shift,uint width,uint bitfield_val)58 static inline uint bitfield_replace(uint reg_val, uint shift, uint width,
59 uint bitfield_val)
60 {
61 uint mask = bitfield_mask(shift, width);
62
63 return (reg_val & ~mask) | ((bitfield_val << shift) & mask);
64 }
65
66 /* Produces a shift of the bitfield given a mask */
bitfield_shift(uint mask)67 static 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 */
bitfield_extract_by_mask(uint reg_val,uint mask)73 static 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 */
bitfield_replace_by_mask(uint reg_val,uint mask,uint bitfield_val)84 static 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 }
91