1*4882a593Smuzhiyun /*
2*4882a593Smuzhiyun * Copyright 2013 Broadcom Corporation.
3*4882a593Smuzhiyun *
4*4882a593Smuzhiyun * SPDX-License-Identifier: GPL-2.0+
5*4882a593Smuzhiyun */
6*4882a593Smuzhiyun
7*4882a593Smuzhiyun /*
8*4882a593Smuzhiyun * Bitfield operations
9*4882a593Smuzhiyun *
10*4882a593Smuzhiyun * These are generic bitfield operations which allow manipulation of variable
11*4882a593Smuzhiyun * width bitfields within a word. One use of this would be to use data tables
12*4882a593Smuzhiyun * to determine how to reprogram fields within R/W hardware registers.
13*4882a593Smuzhiyun *
14*4882a593Smuzhiyun * Example:
15*4882a593Smuzhiyun *
16*4882a593Smuzhiyun * old_reg_val
17*4882a593Smuzhiyun * +--------+----+---+--+-----+----------+
18*4882a593Smuzhiyun * | | | | | old | |
19*4882a593Smuzhiyun * +--------+----+---+--+-----+----------+
20*4882a593Smuzhiyun *
21*4882a593Smuzhiyun * new_reg_val
22*4882a593Smuzhiyun * +--------+----+---+--+-----+----------+
23*4882a593Smuzhiyun * | | | | | new | |
24*4882a593Smuzhiyun * +--------+----+---+--+-----+----------+
25*4882a593Smuzhiyun *
26*4882a593Smuzhiyun * mask = bitfield_mask(10, 5);
27*4882a593Smuzhiyun * old = bitfield_extract(old_reg_val, 10, 5);
28*4882a593Smuzhiyun * new_reg_val = bitfield_replace(old_reg_val, 10, 5, new);
29*4882a593Smuzhiyun *
30*4882a593Smuzhiyun * or
31*4882a593Smuzhiyun *
32*4882a593Smuzhiyun * mask = bitfield_mask(10, 5);
33*4882a593Smuzhiyun * old = bitfield_extract_by_mask(old_reg_val, mask);
34*4882a593Smuzhiyun * new_reg_val = bitfield_replace_by_mask(old_reg_val, mask, new);
35*4882a593Smuzhiyun *
36*4882a593Smuzhiyun * The numbers 10 and 5 could for example come from data
37*4882a593Smuzhiyun * tables which describe all bitfields in all registers.
38*4882a593Smuzhiyun */
39*4882a593Smuzhiyun
40*4882a593Smuzhiyun #include <linux/types.h>
41*4882a593Smuzhiyun
42*4882a593Smuzhiyun /* Produces a mask of set bits covering a range of a uint value */
bitfield_mask(uint shift,uint width)43*4882a593Smuzhiyun static inline uint bitfield_mask(uint shift, uint width)
44*4882a593Smuzhiyun {
45*4882a593Smuzhiyun return ((1 << width) - 1) << shift;
46*4882a593Smuzhiyun }
47*4882a593Smuzhiyun
48*4882a593Smuzhiyun /* Extract the value of a bitfield found within a given register value */
bitfield_extract(uint reg_val,uint shift,uint width)49*4882a593Smuzhiyun static inline uint bitfield_extract(uint reg_val, uint shift, uint width)
50*4882a593Smuzhiyun {
51*4882a593Smuzhiyun return (reg_val & bitfield_mask(shift, width)) >> shift;
52*4882a593Smuzhiyun }
53*4882a593Smuzhiyun
54*4882a593Smuzhiyun /*
55*4882a593Smuzhiyun * Replace the value of a bitfield found within a given register value
56*4882a593Smuzhiyun * Returns the newly modified uint value with the replaced field.
57*4882a593Smuzhiyun */
bitfield_replace(uint reg_val,uint shift,uint width,uint bitfield_val)58*4882a593Smuzhiyun static inline uint bitfield_replace(uint reg_val, uint shift, uint width,
59*4882a593Smuzhiyun uint bitfield_val)
60*4882a593Smuzhiyun {
61*4882a593Smuzhiyun uint mask = bitfield_mask(shift, width);
62*4882a593Smuzhiyun
63*4882a593Smuzhiyun return (reg_val & ~mask) | ((bitfield_val << shift) & mask);
64*4882a593Smuzhiyun }
65*4882a593Smuzhiyun
66*4882a593Smuzhiyun /* Produces a shift of the bitfield given a mask */
bitfield_shift(uint mask)67*4882a593Smuzhiyun static inline uint bitfield_shift(uint mask)
68*4882a593Smuzhiyun {
69*4882a593Smuzhiyun return mask ? ffs(mask) - 1 : 0;
70*4882a593Smuzhiyun }
71*4882a593Smuzhiyun
72*4882a593Smuzhiyun /* Extract the value of a bitfield found within a given register value */
bitfield_extract_by_mask(uint reg_val,uint mask)73*4882a593Smuzhiyun static inline uint bitfield_extract_by_mask(uint reg_val, uint mask)
74*4882a593Smuzhiyun {
75*4882a593Smuzhiyun uint shift = bitfield_shift(mask);
76*4882a593Smuzhiyun
77*4882a593Smuzhiyun return (reg_val & mask) >> shift;
78*4882a593Smuzhiyun }
79*4882a593Smuzhiyun
80*4882a593Smuzhiyun /*
81*4882a593Smuzhiyun * Replace the value of a bitfield found within a given register value
82*4882a593Smuzhiyun * Returns the newly modified uint value with the replaced field.
83*4882a593Smuzhiyun */
bitfield_replace_by_mask(uint reg_val,uint mask,uint bitfield_val)84*4882a593Smuzhiyun static inline uint bitfield_replace_by_mask(uint reg_val, uint mask,
85*4882a593Smuzhiyun uint bitfield_val)
86*4882a593Smuzhiyun {
87*4882a593Smuzhiyun uint shift = bitfield_shift(mask);
88*4882a593Smuzhiyun
89*4882a593Smuzhiyun return (reg_val & ~mask) | ((bitfield_val << shift) & mask);
90*4882a593Smuzhiyun }
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