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