staging: slicoss: fix eeprom checksum code
Rewrite slic_eeprom_cksum() to fix bugs and make readable. This patch
technically has no effect on the user as failed eeprom checksums are
ignored anyway.
The original implementation had the following issues:
1. 2 of the 3 unrolled loops had the following bug:
while ((len -= 32) >= 0) {
[...]
sum += w[15];
w = (u16 *)((ulong) w + 16); /* verify */
}
This processes 32-bytes of data but only increments the word
pointer by 16 bytes. Fixing both of these bugs seems to fix
slic_eeprom_cksum().
2. Non-descriptive variable names, use of unions, and macros that
change local state make the code difficult to read.
3. The checksum loop is unrolled which makes the code harder to
reason about while providing small performance improvement:
- max eeprom length is 0x80 bytes (MAX_EECODE_SIZE), that's
only 0x40 iterations
- checksum is only computed during pci probe(), so not very
often
Tested on Mojave card
Signed-off-by: David Matlack <matlackdavid@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1 file changed