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);