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/types.h>
40
41 /* Produces a mask of set bits covering a range of a uint value */
bitfield_mask(uint shift,uint width)42 static inline uint bitfield_mask(uint shift, uint width)
43 {
44 return ((1 << width) - 1) << shift;
45 }
46
47 /* Extract the value of a bitfield found within a given register value */
bitfield_extract(uint reg_val,uint shift,uint width)48 static inline uint bitfield_extract(uint reg_val, uint shift, uint width)
49 {
50 return (reg_val & bitfield_mask(shift, width)) >> shift;
51 }
52
53 /*
54 * Replace the value of a bitfield found within a given register value
55 * Returns the newly modified uint value with the replaced field.
56 */
bitfield_replace(uint reg_val,uint shift,uint width,uint bitfield_val)57 static inline uint bitfield_replace(uint reg_val, uint shift, uint width,
58 uint bitfield_val)
59 {
60 uint mask = bitfield_mask(shift, width);
61
62 return (reg_val & ~mask) | ((bitfield_val << shift) & mask);
63 }
64
65 /* Produces a shift of the bitfield given a mask */
bitfield_shift(uint mask)66 static inline uint bitfield_shift(uint mask)
67 {
68 return mask ? ffs(mask) - 1 : 0;
69 }
70
71 /* Extract the value of a bitfield found within a given register value */
bitfield_extract_by_mask(uint reg_val,uint mask)72 static inline uint bitfield_extract_by_mask(uint reg_val, uint mask)
73 {
74 uint shift = bitfield_shift(mask);
75
76 return (reg_val & mask) >> shift;
77 }
78
79 /*
80 * Replace the value of a bitfield found within a given register value
81 * Returns the newly modified uint value with the replaced field.
82 */
bitfield_replace_by_mask(uint reg_val,uint mask,uint bitfield_val)83 static inline uint bitfield_replace_by_mask(uint reg_val, uint mask,
84 uint bitfield_val)
85 {
86 uint shift = bitfield_shift(mask);
87
88 return (reg_val & ~mask) | ((bitfield_val << shift) & mask);
89 }
90