xref: /openbmc/u-boot/include/bitfield.h (revision e8f80a5a)
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