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 <arch/chip.h>
 16
 17#include <linux/types.h>
 18#include <linux/string.h>
 19#include <linux/module.h>
 20
 21#undef memset
 22
 23void *memset(void *s, int c, size_t n)
 24{
 25	uint64_t *out64;
 26	int n64, to_align64;
 27	uint64_t v64;
 28	uint8_t *out8 = s;
 29
 30	/* Experimentation shows that a trivial tight loop is a win up until
 31	 * around a size of 20, where writing a word at a time starts to win.
 32	 */
 33#define BYTE_CUTOFF 20
 34
 35#if BYTE_CUTOFF < 7
 36	/* This must be at least at least this big, or some code later
 37	 * on doesn't work.
 38	 */
 39#error "BYTE_CUTOFF is too small"
 40#endif
 41
 42	if (n < BYTE_CUTOFF) {
 43		/* Strangely, this turns out to be the tightest way to
 44		 * write this loop.
 45		 */
 46		if (n != 0) {
 47			do {
 48				/* Strangely, combining these into one line
 49				 * performs worse.
 50				 */
 51				*out8 = c;
 52				out8++;
 53			} while (--n != 0);
 54		}
 55
 56		return s;
 57	}
 58
 59	/* Align 'out8'. We know n >= 7 so this won't write past the end. */
 60	while (((uintptr_t) out8 & 7) != 0) {
 61		*out8++ = c;
 62		--n;
 63	}
 64
 65	/* Align 'n'. */
 66	while (n & 7)
 67		out8[--n] = c;
 68
 69	out64 = (uint64_t *) out8;
 70	n64 = n >> 3;
 71
 72	/* Tile input byte out to 64 bits. */
 73	/* KLUDGE */
 74	v64 = 0x0101010101010101ULL * (uint8_t)c;
 75
 76	/* This must be at least 8 or the following loop doesn't work. */
 77#define CACHE_LINE_SIZE_IN_DOUBLEWORDS (CHIP_L2_LINE_SIZE() / 8)
 78
 79	/* Determine how many words we need to emit before the 'out32'
 80	 * pointer becomes aligned modulo the cache line size.
 81	 */
 82	to_align64 = (-((uintptr_t)out64 >> 3)) &
 83		(CACHE_LINE_SIZE_IN_DOUBLEWORDS - 1);
 84
 85	/* Only bother aligning and using wh64 if there is at least
 86	 * one full cache line to process.  This check also prevents
 87	 * overrunning the end of the buffer with alignment words.
 88	 */
 89	if (to_align64 <= n64 - CACHE_LINE_SIZE_IN_DOUBLEWORDS) {
 90		int lines_left;
 91
 92		/* Align out64 mod the cache line size so we can use wh64. */
 93		n64 -= to_align64;
 94		for (; to_align64 != 0; to_align64--) {
 95			*out64 = v64;
 96			out64++;
 97		}
 98
 99		/* Use unsigned divide to turn this into a right shift. */
100		lines_left = (unsigned)n64 / CACHE_LINE_SIZE_IN_DOUBLEWORDS;
101
102		do {
103			/* Only wh64 a few lines at a time, so we don't
104			 * exceed the maximum number of victim lines.
105			 */
106			int x = ((lines_left < CHIP_MAX_OUTSTANDING_VICTIMS())
107				  ? lines_left
108				  : CHIP_MAX_OUTSTANDING_VICTIMS());
109			uint64_t *wh = out64;
110			int i = x;
111			int j;
112
113			lines_left -= x;
114
115			do {
116				__insn_wh64(wh);
117				wh += CACHE_LINE_SIZE_IN_DOUBLEWORDS;
118			} while (--i);
119
120			for (j = x * (CACHE_LINE_SIZE_IN_DOUBLEWORDS / 4);
121			     j != 0; j--) {
122				*out64++ = v64;
123				*out64++ = v64;
124				*out64++ = v64;
125				*out64++ = v64;
126			}
127		} while (lines_left != 0);
128
129		/* We processed all full lines above, so only this many
130		 * words remain to be processed.
131		 */
132		n64 &= CACHE_LINE_SIZE_IN_DOUBLEWORDS - 1;
133	}
134
135	/* Now handle any leftover values. */
136	if (n64 != 0) {
137		do {
138			*out64 = v64;
139			out64++;
140		} while (--n64 != 0);
141	}
142
143	return s;
144}
145EXPORT_SYMBOL(memset);