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#include <arch/chip.h>
19#include "string-endian.h"
20
21void *memset(void *s, int c, size_t n)
22{
23	uint64_t *out64;
24	int n64, to_align64;
25	uint64_t v64;
26	uint8_t *out8 = s;
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 < 7
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 >= 7 so this won't write past the end. */
58	while (((uintptr_t) out8 & 7) != 0) {
59		*out8++ = c;
60		--n;
61	}
62
63	/* Align 'n'. */
64	while (n & 7)
65		out8[--n] = c;
66
67	out64 = (uint64_t *) out8;
68	n64 = n >> 3;
69
70	/* Tile input byte out to 64 bits. */
71	v64 = copy_byte(c);
72
73	/* This must be at least 8 or the following loop doesn't work. */
74#define CACHE_LINE_SIZE_IN_DOUBLEWORDS (CHIP_L2_LINE_SIZE() / 8)
75
76	/* Determine how many words we need to emit before the 'out32'
77	 * pointer becomes aligned modulo the cache line size.
78	 */
79	to_align64 = (-((uintptr_t)out64 >> 3)) &
80		(CACHE_LINE_SIZE_IN_DOUBLEWORDS - 1);
81
82	/* Only bother aligning and using wh64 if there is at least
83	 * one full cache line to process.  This check also prevents
84	 * overrunning the end of the buffer with alignment words.
85	 */
86	if (to_align64 <= n64 - CACHE_LINE_SIZE_IN_DOUBLEWORDS) {
87		int lines_left;
88
89		/* Align out64 mod the cache line size so we can use wh64. */
90		n64 -= to_align64;
91		for (; to_align64 != 0; to_align64--) {
92			*out64 = v64;
93			out64++;
94		}
95
96		/* Use unsigned divide to turn this into a right shift. */
97		lines_left = (unsigned)n64 / CACHE_LINE_SIZE_IN_DOUBLEWORDS;
98
99		do {
100			/* Only wh64 a few lines at a time, so we don't
101			 * exceed the maximum number of victim lines.
102			 */
103			int x = ((lines_left < CHIP_MAX_OUTSTANDING_VICTIMS())
104				  ? lines_left
105				  : CHIP_MAX_OUTSTANDING_VICTIMS());
106			uint64_t *wh = out64;
107			int i = x;
108			int j;
109
110			lines_left -= x;
111
112			do {
113				__insn_wh64(wh);
114				wh += CACHE_LINE_SIZE_IN_DOUBLEWORDS;
115			} while (--i);
116
117			for (j = x * (CACHE_LINE_SIZE_IN_DOUBLEWORDS / 4);
118			     j != 0; j--) {
119				*out64++ = v64;
120				*out64++ = v64;
121				*out64++ = v64;
122				*out64++ = v64;
123			}
124		} while (lines_left != 0);
125
126		/* We processed all full lines above, so only this many
127		 * words remain to be processed.
128		 */
129		n64 &= CACHE_LINE_SIZE_IN_DOUBLEWORDS - 1;
130	}
131
132	/* Now handle any leftover values. */
133	if (n64 != 0) {
134		do {
135			*out64 = v64;
136			out64++;
137		} while (--n64 != 0);
138	}
139
140	return s;
141}
142EXPORT_SYMBOL(memset);
143