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 * Support code for the main lib/checksum.c.
 14 */
 15
 16#include <net/checksum.h>
 17#include <linux/module.h>
 18
 19static inline unsigned int longto16(unsigned long x)
 20{
 21	unsigned long ret;
 22#ifdef __tilegx__
 23	ret = __insn_v2sadu(x, 0);
 24	ret = __insn_v2sadu(ret, 0);
 25#else
 26	ret = __insn_sadh_u(x, 0);
 27	ret = __insn_sadh_u(ret, 0);
 28#endif
 29	return ret;
 30}
 31
 32__wsum do_csum(const unsigned char *buff, int len)
 33{
 34	int odd, count;
 35	unsigned long result = 0;
 36
 37	if (len <= 0)
 38		goto out;
 39	odd = 1 & (unsigned long) buff;
 40	if (odd) {
 41		result = (*buff << 8);
 42		len--;
 43		buff++;
 44	}
 45	count = len >> 1;		/* nr of 16-bit words.. */
 46	if (count) {
 47		if (2 & (unsigned long) buff) {
 48			result += *(const unsigned short *)buff;
 49			count--;
 50			len -= 2;
 51			buff += 2;
 52		}
 53		count >>= 1;		/* nr of 32-bit words.. */
 54		if (count) {
 55#ifdef __tilegx__
 56			if (4 & (unsigned long) buff) {
 57				unsigned int w = *(const unsigned int *)buff;
 58				result = __insn_v2sadau(result, w, 0);
 59				count--;
 60				len -= 4;
 61				buff += 4;
 62			}
 63			count >>= 1;		/* nr of 64-bit words.. */
 64#endif
 65
 66			/*
 67			 * This algorithm could wrap around for very
 68			 * large buffers, but those should be impossible.
 69			 */
 70			BUG_ON(count >= 65530);
 71
 72			while (count) {
 73				unsigned long w = *(const unsigned long *)buff;
 74				count--;
 75				buff += sizeof(w);
 76#ifdef __tilegx__
 77				result = __insn_v2sadau(result, w, 0);
 78#else
 79				result = __insn_sadah_u(result, w, 0);
 80#endif
 81			}
 82#ifdef __tilegx__
 83			if (len & 4) {
 84				unsigned int w = *(const unsigned int *)buff;
 85				result = __insn_v2sadau(result, w, 0);
 86				buff += 4;
 87			}
 88#endif
 89		}
 90		if (len & 2) {
 91			result += *(const unsigned short *) buff;
 92			buff += 2;
 93		}
 94	}
 95	if (len & 1)
 96		result += *buff;
 97	result = longto16(result);
 98	if (odd)
 99		result = swab16(result);
100out:
101	return result;
102}