diff options
Diffstat (limited to 'ecc.h')
| -rw-r--r-- | ecc.h | 77 |
1 files changed, 77 insertions, 0 deletions
@@ -0,0 +1,77 @@ +/* + * Calculate Error-correcting Codes. Used by NAND Flash controllers + * (not by NAND chips). + * + * Copyright (c) 2006 Openedhand Ltd. + * Written by Andrzej Zaborowski <balrog@zabor.org> + * + * This code is licensed under the GNU GPL v2. + */ + +struct ecc_state_s { + uint8_t cp; /* Column parity */ + uint16_t lp[2]; /* Line parity */ + uint16_t count; +}; + +/* + * Pre-calculated 256-way 1 byte column parity. Table borrowed from Linux. + */ +static const uint8_t nand_ecc_precalc_table[] = { + 0x00, 0x55, 0x56, 0x03, 0x59, 0x0c, 0x0f, 0x5a, + 0x5a, 0x0f, 0x0c, 0x59, 0x03, 0x56, 0x55, 0x00, + 0x65, 0x30, 0x33, 0x66, 0x3c, 0x69, 0x6a, 0x3f, + 0x3f, 0x6a, 0x69, 0x3c, 0x66, 0x33, 0x30, 0x65, + 0x66, 0x33, 0x30, 0x65, 0x3f, 0x6a, 0x69, 0x3c, + 0x3c, 0x69, 0x6a, 0x3f, 0x65, 0x30, 0x33, 0x66, + 0x03, 0x56, 0x55, 0x00, 0x5a, 0x0f, 0x0c, 0x59, + 0x59, 0x0c, 0x0f, 0x5a, 0x00, 0x55, 0x56, 0x03, + 0x69, 0x3c, 0x3f, 0x6a, 0x30, 0x65, 0x66, 0x33, + 0x33, 0x66, 0x65, 0x30, 0x6a, 0x3f, 0x3c, 0x69, + 0x0c, 0x59, 0x5a, 0x0f, 0x55, 0x00, 0x03, 0x56, + 0x56, 0x03, 0x00, 0x55, 0x0f, 0x5a, 0x59, 0x0c, + 0x0f, 0x5a, 0x59, 0x0c, 0x56, 0x03, 0x00, 0x55, + 0x55, 0x00, 0x03, 0x56, 0x0c, 0x59, 0x5a, 0x0f, + 0x6a, 0x3f, 0x3c, 0x69, 0x33, 0x66, 0x65, 0x30, + 0x30, 0x65, 0x66, 0x33, 0x69, 0x3c, 0x3f, 0x6a, + 0x6a, 0x3f, 0x3c, 0x69, 0x33, 0x66, 0x65, 0x30, + 0x30, 0x65, 0x66, 0x33, 0x69, 0x3c, 0x3f, 0x6a, + 0x0f, 0x5a, 0x59, 0x0c, 0x56, 0x03, 0x00, 0x55, + 0x55, 0x00, 0x03, 0x56, 0x0c, 0x59, 0x5a, 0x0f, + 0x0c, 0x59, 0x5a, 0x0f, 0x55, 0x00, 0x03, 0x56, + 0x56, 0x03, 0x00, 0x55, 0x0f, 0x5a, 0x59, 0x0c, + 0x69, 0x3c, 0x3f, 0x6a, 0x30, 0x65, 0x66, 0x33, + 0x33, 0x66, 0x65, 0x30, 0x6a, 0x3f, 0x3c, 0x69, + 0x03, 0x56, 0x55, 0x00, 0x5a, 0x0f, 0x0c, 0x59, + 0x59, 0x0c, 0x0f, 0x5a, 0x00, 0x55, 0x56, 0x03, + 0x66, 0x33, 0x30, 0x65, 0x3f, 0x6a, 0x69, 0x3c, + 0x3c, 0x69, 0x6a, 0x3f, 0x65, 0x30, 0x33, 0x66, + 0x65, 0x30, 0x33, 0x66, 0x3c, 0x69, 0x6a, 0x3f, + 0x3f, 0x6a, 0x69, 0x3c, 0x66, 0x33, 0x30, 0x65, + 0x00, 0x55, 0x56, 0x03, 0x59, 0x0c, 0x0f, 0x5a, + 0x5a, 0x0f, 0x0c, 0x59, 0x03, 0x56, 0x55, 0x00, +}; + +/* Update ECC parity count. */ +static inline uint8_t ecc_digest(struct ecc_state_s *s, uint8_t sample) +{ + uint8_t idx = nand_ecc_precalc_table[sample]; + + s->cp ^= idx & 0x3f; + if (idx & 0x40) { + s->lp[0] ^= ~s->count; + s->lp[1] ^= s->count; + } + s->count ++; + + return sample; +} + +/* Reinitialise the counters. */ +static inline void ecc_reset(struct ecc_state_s *s) +{ + s->lp[0] = 0x0000; + s->lp[1] = 0x0000; + s->cp = 0x00; + s->count = 0; +} |