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1/*
2 * Copyright 2011 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/* EXPORT_SYMBOL() is in arch/tile/lib/exports.c since this should be asm. */
19
20/* Must be 8 bytes in size. */
21#define word_t uint64_t
22
23#if CHIP_L2_LINE_SIZE() != 64 && CHIP_L2_LINE_SIZE() != 128
24#error "Assumes 64 or 128 byte line size"
25#endif
26
27/* How many cache lines ahead should we prefetch? */
28#define PREFETCH_LINES_AHEAD 3
29
30/*
31 * Provide "base versions" of load and store for the normal code path.
32 * The kernel provides other versions for userspace copies.
33 */
34#define ST(p, v) (*(p) = (v))
35#define LD(p) (*(p))
36
37#ifndef USERCOPY_FUNC
38#define ST1 ST
39#define ST2 ST
40#define ST4 ST
41#define ST8 ST
42#define LD1 LD
43#define LD2 LD
44#define LD4 LD
45#define LD8 LD
46#define RETVAL dstv
47void *memcpy(void *__restrict dstv, const void *__restrict srcv, size_t n)
48#else
49/*
50 * Special kernel version will provide implementation of the LDn/STn
51 * macros to return a count of uncopied bytes due to mm fault.
52 */
53#define RETVAL 0
54int USERCOPY_FUNC(void *__restrict dstv, const void *__restrict srcv, size_t n)
55#endif
56{
57 char *__restrict dst1 = (char *)dstv;
58 const char *__restrict src1 = (const char *)srcv;
59 const char *__restrict src1_end;
60 const char *__restrict prefetch;
61 word_t *__restrict dst8; /* 8-byte pointer to destination memory. */
62 word_t final; /* Final bytes to write to trailing word, if any */
63 long i;
64
65 if (n < 16) {
66 for (; n; n--)
67 ST1(dst1++, LD1(src1++));
68 return RETVAL;
69 }
70
71 /*
72 * Locate the end of source memory we will copy. Don't
73 * prefetch past this.
74 */
75 src1_end = src1 + n - 1;
76
77 /* Prefetch ahead a few cache lines, but not past the end. */
78 prefetch = src1;
79 for (i = 0; i < PREFETCH_LINES_AHEAD; i++) {
80 __insn_prefetch(prefetch);
81 prefetch += CHIP_L2_LINE_SIZE();
82 prefetch = (prefetch > src1_end) ? prefetch : src1;
83 }
84
85 /* Copy bytes until dst is word-aligned. */
86 for (; (uintptr_t)dst1 & (sizeof(word_t) - 1); n--)
87 ST1(dst1++, LD1(src1++));
88
89 /* 8-byte pointer to destination memory. */
90 dst8 = (word_t *)dst1;
91
92 if (__builtin_expect((uintptr_t)src1 & (sizeof(word_t) - 1), 0)) {
93 /*
94 * Misaligned copy. Copy 8 bytes at a time, but don't
95 * bother with other fanciness.
96 *
97 * TODO: Consider prefetching and using wh64 as well.
98 */
99
100 /* Create an aligned src8. */
101 const word_t *__restrict src8 =
102 (const word_t *)((uintptr_t)src1 & -sizeof(word_t));
103 word_t b;
104
105 word_t a = LD8(src8++);
106 for (; n >= sizeof(word_t); n -= sizeof(word_t)) {
107 b = LD8(src8++);
108 a = __insn_dblalign(a, b, src1);
109 ST8(dst8++, a);
110 a = b;
111 }
112
113 if (n == 0)
114 return RETVAL;
115
116 b = ((const char *)src8 <= src1_end) ? *src8 : 0;
117
118 /*
119 * Final source bytes to write to trailing partial
120 * word, if any.
121 */
122 final = __insn_dblalign(a, b, src1);
123 } else {
124 /* Aligned copy. */
125
126 const word_t* __restrict src8 = (const word_t *)src1;
127
128 /* src8 and dst8 are both word-aligned. */
129 if (n >= CHIP_L2_LINE_SIZE()) {
130 /* Copy until 'dst' is cache-line-aligned. */
131 for (; (uintptr_t)dst8 & (CHIP_L2_LINE_SIZE() - 1);
132 n -= sizeof(word_t))
133 ST8(dst8++, LD8(src8++));
134
135 for (; n >= CHIP_L2_LINE_SIZE(); ) {
136 __insn_wh64(dst8);
137
138 /*
139 * Prefetch and advance to next line
140 * to prefetch, but don't go past the end
141 */
142 __insn_prefetch(prefetch);
143 prefetch += CHIP_L2_LINE_SIZE();
144 prefetch = (prefetch > src1_end) ? prefetch :
145 (const char *)src8;
146
147 /*
148 * Copy an entire cache line. Manually
149 * unrolled to avoid idiosyncracies of
150 * compiler unrolling.
151 */
152#define COPY_WORD(offset) ({ ST8(dst8+offset, LD8(src8+offset)); n -= 8; })
153 COPY_WORD(0);
154 COPY_WORD(1);
155 COPY_WORD(2);
156 COPY_WORD(3);
157 COPY_WORD(4);
158 COPY_WORD(5);
159 COPY_WORD(6);
160 COPY_WORD(7);
161#if CHIP_L2_LINE_SIZE() == 128
162 COPY_WORD(8);
163 COPY_WORD(9);
164 COPY_WORD(10);
165 COPY_WORD(11);
166 COPY_WORD(12);
167 COPY_WORD(13);
168 COPY_WORD(14);
169 COPY_WORD(15);
170#elif CHIP_L2_LINE_SIZE() != 64
171# error Fix code that assumes particular L2 cache line sizes
172#endif
173
174 dst8 += CHIP_L2_LINE_SIZE() / sizeof(word_t);
175 src8 += CHIP_L2_LINE_SIZE() / sizeof(word_t);
176 }
177 }
178
179 for (; n >= sizeof(word_t); n -= sizeof(word_t))
180 ST8(dst8++, LD8(src8++));
181
182 if (__builtin_expect(n == 0, 1))
183 return RETVAL;
184
185 final = LD8(src8);
186 }
187
188 /* n != 0 if we get here. Write out any trailing bytes. */
189 dst1 = (char *)dst8;
190#ifndef __BIG_ENDIAN__
191 if (n & 4) {
192 ST4((uint32_t *)dst1, final);
193 dst1 += 4;
194 final >>= 32;
195 n &= 3;
196 }
197 if (n & 2) {
198 ST2((uint16_t *)dst1, final);
199 dst1 += 2;
200 final >>= 16;
201 n &= 1;
202 }
203 if (n)
204 ST1((uint8_t *)dst1, final);
205#else
206 if (n & 4) {
207 ST4((uint32_t *)dst1, final >> 32);
208 dst1 += 4;
209 }
210 else
211 {
212 final >>= 32;
213 }
214 if (n & 2) {
215 ST2((uint16_t *)dst1, final >> 16);
216 dst1 += 2;
217 }
218 else
219 {
220 final >>= 16;
221 }
222 if (n & 1)
223 ST1((uint8_t *)dst1, final >> 8);
224#endif
225
226 return RETVAL;
227}
228
229#ifdef USERCOPY_FUNC
230#undef ST1
231#undef ST2
232#undef ST4
233#undef ST8
234#undef LD1
235#undef LD2
236#undef LD4
237#undef LD8
238#undef USERCOPY_FUNC
239#endif