arch/tile/lib/checksum.c

   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
  19 __wsum do_csum(const unsigned char *buff, int len)
  20 {
  21         int odd, count;
  22         unsigned long result = 0;
  23
  24         if (len <= 0)
  25                 goto out;
  26         odd = 1 & (unsigned long) buff;
  27         if (odd) {
  28                 result = (*buff << 8);
  29                 len--;
  30                 buff++;
  31         }
  32         count = len >> 1;               /* nr of 16-bit words.. */
  33         if (count) {
  34                 if (2 & (unsigned long) buff) {
  35                         result += *(const unsigned short *)buff;
  36                         count--;
  37                         len -= 2;
  38                         buff += 2;
  39                 }
  40                 count >>= 1;            /* nr of 32-bit words.. */
  41                 if (count) {
  42 #ifdef __tilegx__
  43                         if (4 & (unsigned long) buff) {
  44                                 unsigned int w = *(const unsigned int *)buff;
  45                                 result = __insn_v2sadau(result, w, 0);
  46                                 count--;
  47                                 len -= 4;
  48                                 buff += 4;
  49                         }
  50                         count >>= 1;            /* nr of 64-bit words.. */
  51 #endif
  52
  53                         /*
  54                          * This algorithm could wrap around for very
  55                          * large buffers, but those should be impossible.
  56                          */
  57                         BUG_ON(count >= 65530);
  58
  59                         while (count) {
  60                                 unsigned long w = *(const unsigned long *)buff;
  61                                 count--;
  62                                 buff += sizeof(w);
  63 #ifdef __tilegx__
  64                                 result = __insn_v2sadau(result, w, 0);
  65 #else
  66                                 result = __insn_sadah_u(result, w, 0);
  67 #endif
  68                         }
  69 #ifdef __tilegx__
  70                         if (len & 4) {
  71                                 unsigned int w = *(const unsigned int *)buff;
  72                                 result = __insn_v2sadau(result, w, 0);
  73                                 buff += 4;
  74                         }
  75 #endif
  76                 }
  77                 if (len & 2) {
  78                         result += *(const unsigned short *) buff;
  79                         buff += 2;
  80                 }
  81         }
  82         if (len & 1)
  83                 result += *buff;
  84         result = csum_long(result);
  85         if (odd)
  86                 result = swab16(result);
  87 out:
  88         return result;
  89 }