1 /*
2 * Copyright 2010 Tilera Corporation. All Rights Reserved.
3 *
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU General Public License
6 * as published by the Free Software Foundation, version 2.
7 *
8 * This program is distributed in the hope that it will be useful, but
9 * WITHOUT ANY WARRANTY; without even the implied warranty of
10 * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
11 * NON INFRINGEMENT. See the GNU General Public License for
12 * more details.
13 */
14
15 #include <linux/types.h>
16 #include <linux/string.h>
17 #include <linux/module.h>
18 #include <arch/chip.h>
19
memset(void * s,int c,size_t n)20 void *memset(void *s, int c, size_t n)
21 {
22 uint32_t *out32;
23 int n32;
24 uint32_t v16, v32;
25 uint8_t *out8 = s;
26 int to_align32;
27
28 /* Experimentation shows that a trivial tight loop is a win up until
29 * around a size of 20, where writing a word at a time starts to win.
30 */
31 #define BYTE_CUTOFF 20
32
33 #if BYTE_CUTOFF < 3
34 /* This must be at least at least this big, or some code later
35 * on doesn't work.
36 */
37 #error "BYTE_CUTOFF is too small"
38 #endif
39
40 if (n < BYTE_CUTOFF) {
41 /* Strangely, this turns out to be the tightest way to
42 * write this loop.
43 */
44 if (n != 0) {
45 do {
46 /* Strangely, combining these into one line
47 * performs worse.
48 */
49 *out8 = c;
50 out8++;
51 } while (--n != 0);
52 }
53
54 return s;
55 }
56
57 /* Align 'out8'. We know n >= 3 so this won't write past the end. */
58 while (((uintptr_t) out8 & 3) != 0) {
59 *out8++ = c;
60 --n;
61 }
62
63 /* Align 'n'. */
64 while (n & 3)
65 out8[--n] = c;
66
67 out32 = (uint32_t *) out8;
68 n32 = n >> 2;
69
70 /* Tile input byte out to 32 bits. */
71 v16 = __insn_intlb(c, c);
72 v32 = __insn_intlh(v16, v16);
73
74 /* This must be at least 8 or the following loop doesn't work. */
75 #define CACHE_LINE_SIZE_IN_WORDS (CHIP_L2_LINE_SIZE() / 4)
76
77 /* Determine how many words we need to emit before the 'out32'
78 * pointer becomes aligned modulo the cache line size.
79 */
80 to_align32 =
81 (-((uintptr_t)out32 >> 2)) & (CACHE_LINE_SIZE_IN_WORDS - 1);
82
83 /* Only bother aligning and using wh64 if there is at least
84 * one full cache line to process. This check also prevents
85 * overrunning the end of the buffer with alignment words.
86 */
87 if (to_align32 <= n32 - CACHE_LINE_SIZE_IN_WORDS) {
88 int lines_left;
89
90 /* Align out32 mod the cache line size so we can use wh64. */
91 n32 -= to_align32;
92 for (; to_align32 != 0; to_align32--) {
93 *out32 = v32;
94 out32++;
95 }
96
97 /* Use unsigned divide to turn this into a right shift. */
98 lines_left = (unsigned)n32 / CACHE_LINE_SIZE_IN_WORDS;
99
100 do {
101 /* Only wh64 a few lines at a time, so we don't
102 * exceed the maximum number of victim lines.
103 */
104 int x = ((lines_left < CHIP_MAX_OUTSTANDING_VICTIMS())
105 ? lines_left
106 : CHIP_MAX_OUTSTANDING_VICTIMS());
107 uint32_t *wh = out32;
108 int i = x;
109 int j;
110
111 lines_left -= x;
112
113 do {
114 __insn_wh64(wh);
115 wh += CACHE_LINE_SIZE_IN_WORDS;
116 } while (--i);
117
118 for (j = x * (CACHE_LINE_SIZE_IN_WORDS / 4);
119 j != 0; j--) {
120 *out32++ = v32;
121 *out32++ = v32;
122 *out32++ = v32;
123 *out32++ = v32;
124 }
125 } while (lines_left != 0);
126
127 /* We processed all full lines above, so only this many
128 * words remain to be processed.
129 */
130 n32 &= CACHE_LINE_SIZE_IN_WORDS - 1;
131 }
132
133 /* Now handle any leftover values. */
134 if (n32 != 0) {
135 do {
136 *out32 = v32;
137 out32++;
138 } while (--n32 != 0);
139 }
140
141 return s;
142 }
143 EXPORT_SYMBOL(memset);
144