Messages in this thread | | | From | Mike Frysinger <> | Date | Thu, 18 Jun 2009 21:19:41 -0400 | Subject | Re: [PATCH 05/17] Blackfin: convert to generic checksum code |
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On Mon, Jun 15, 2009 at 07:04, Arnd Bergmann wrote: > On Sunday 14 June 2009, Mike Frysinger wrote: >> The Blackfin port only implemented an optimized version of the >> csum_tcpudp_nofold function, so convert everything else to the new >> generic code. >> >> Signed-off-by: Mike Frysinger <vapier@gentoo.org> > > Have you tested this one well? I was as careful as possible with the > version I added, but it was basically only tested on microblaze, which > has a different endianess from blackfin. Some areas of the code may be > sensitive to this.
i did some tests and it looks like do_csum() is broken :(
here's the input: do_csum({ 0xff 0xfb 0x01 }, 3)
and here's the output: Blackfin: 0xfc00 generic: 0xfcff
if i run the two funcs on my x86, i see similar behavior. the attached csum-test.c contains the csum code from lib/checksum.c and arch/blackfin/lib/checksum.c and shows the problem. -mike #include <stdio.h>
static inline unsigned short gen_from32to16(unsigned long x) { /* add up 16-bit and 16-bit for 16+c bit */ x = (x & 0xffff) + (x >> 16); /* add up carry.. */ x = (x & 0xffff) + (x >> 16); return x; }
static unsigned int gen_do_csum(const unsigned char *buff, int len) { int odd, count; unsigned long result = 0;
if (len <= 0) goto out; odd = 1 & (unsigned long) buff; if (odd) { result = *buff; len--; buff++; } count = len >> 1; /* nr of 16-bit words.. */ if (count) { if (2 & (unsigned long) buff) { result += *(unsigned short *) buff; count--; len -= 2; buff += 2; } count >>= 1; /* nr of 32-bit words.. */ if (count) { unsigned long carry = 0; do { unsigned long w = *(unsigned long *) buff; count--; buff += 4; result += carry; result += w; carry = (w > result); } while (count); result += carry; result = (result & 0xffff) + (result >> 16); } if (len & 2) { result += *(unsigned short *) buff; buff += 2; } } if (len & 1) result += (*buff << 8); result = gen_from32to16(result); if (odd) result = ((result >> 8) & 0xff) | ((result & 0xff) << 8); out: return result; }
static unsigned short bf_do_csum(const unsigned char *buff, int len) { register unsigned long sum = 0; int swappem = 0;
if (1 & (unsigned long)buff) { sum = *buff << 8; buff++; len--; ++swappem; }
while (len > 1) { sum += *(unsigned short *)buff; buff += 2; len -= 2; }
if (len > 0) sum += *buff;
/* Fold 32-bit sum to 16 bits */ while (sum >> 16) sum = (sum & 0xffff) + (sum >> 16);
if (swappem) sum = ((sum & 0xff00) >> 8) + ((sum & 0x00ff) << 8);
return sum;
}
int main() { unsigned char buf[] = { 0xff, 0xfb, 0x01 }; unsigned short gen = gen_do_csum(buf, 3); unsigned short bf = bf_do_csum(buf, 3); printf("%x vs %x\n", gen, bf); return 0; }
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