1 /* SPDX-License-Identifier: GPL-2.0-or-later WITH eCos-exception-2.0 */
4 * This file contains an ECC algorithm from Toshiba that allows for detection
5 * and correction of 1-bit errors in a 256 byte block of data.
7 * [ Extracted from the initial code found in some early Linux versions.
8 * The current Linux code is bigger while being faster, but this is of
9 * no real benefit when the bottleneck largely remains the JTAG link. ]
11 * Copyright (C) 2000-2004 Steven J. Hill (sjhill at realitydiluted.com)
12 * Toshiba America Electronics Components, Inc.
14 * Copyright (C) 2006 Thomas Gleixner <tglx at linutronix.de>
24 * Pre-calculated 256-way 1 byte column parity
26 static const uint8_t nand_ecc_precalc_table[] = {
27 0x00, 0x55, 0x56, 0x03, 0x59, 0x0c, 0x0f, 0x5a, 0x5a, 0x0f, 0x0c, 0x59, 0x03, 0x56, 0x55, 0x00,
28 0x65, 0x30, 0x33, 0x66, 0x3c, 0x69, 0x6a, 0x3f, 0x3f, 0x6a, 0x69, 0x3c, 0x66, 0x33, 0x30, 0x65,
29 0x66, 0x33, 0x30, 0x65, 0x3f, 0x6a, 0x69, 0x3c, 0x3c, 0x69, 0x6a, 0x3f, 0x65, 0x30, 0x33, 0x66,
30 0x03, 0x56, 0x55, 0x00, 0x5a, 0x0f, 0x0c, 0x59, 0x59, 0x0c, 0x0f, 0x5a, 0x00, 0x55, 0x56, 0x03,
31 0x69, 0x3c, 0x3f, 0x6a, 0x30, 0x65, 0x66, 0x33, 0x33, 0x66, 0x65, 0x30, 0x6a, 0x3f, 0x3c, 0x69,
32 0x0c, 0x59, 0x5a, 0x0f, 0x55, 0x00, 0x03, 0x56, 0x56, 0x03, 0x00, 0x55, 0x0f, 0x5a, 0x59, 0x0c,
33 0x0f, 0x5a, 0x59, 0x0c, 0x56, 0x03, 0x00, 0x55, 0x55, 0x00, 0x03, 0x56, 0x0c, 0x59, 0x5a, 0x0f,
34 0x6a, 0x3f, 0x3c, 0x69, 0x33, 0x66, 0x65, 0x30, 0x30, 0x65, 0x66, 0x33, 0x69, 0x3c, 0x3f, 0x6a,
35 0x6a, 0x3f, 0x3c, 0x69, 0x33, 0x66, 0x65, 0x30, 0x30, 0x65, 0x66, 0x33, 0x69, 0x3c, 0x3f, 0x6a,
36 0x0f, 0x5a, 0x59, 0x0c, 0x56, 0x03, 0x00, 0x55, 0x55, 0x00, 0x03, 0x56, 0x0c, 0x59, 0x5a, 0x0f,
37 0x0c, 0x59, 0x5a, 0x0f, 0x55, 0x00, 0x03, 0x56, 0x56, 0x03, 0x00, 0x55, 0x0f, 0x5a, 0x59, 0x0c,
38 0x69, 0x3c, 0x3f, 0x6a, 0x30, 0x65, 0x66, 0x33, 0x33, 0x66, 0x65, 0x30, 0x6a, 0x3f, 0x3c, 0x69,
39 0x03, 0x56, 0x55, 0x00, 0x5a, 0x0f, 0x0c, 0x59, 0x59, 0x0c, 0x0f, 0x5a, 0x00, 0x55, 0x56, 0x03,
40 0x66, 0x33, 0x30, 0x65, 0x3f, 0x6a, 0x69, 0x3c, 0x3c, 0x69, 0x6a, 0x3f, 0x65, 0x30, 0x33, 0x66,
41 0x65, 0x30, 0x33, 0x66, 0x3c, 0x69, 0x6a, 0x3f, 0x3f, 0x6a, 0x69, 0x3c, 0x66, 0x33, 0x30, 0x65,
42 0x00, 0x55, 0x56, 0x03, 0x59, 0x0c, 0x0f, 0x5a, 0x5a, 0x0f, 0x0c, 0x59, 0x03, 0x56, 0x55, 0x00
46 * nand_calculate_ecc - Calculate 3-byte ECC for 256-byte block
48 int nand_calculate_ecc(struct nand_device *nand, const uint8_t *dat, uint8_t *ecc_code)
50 uint8_t idx, reg1, reg2, reg3, tmp1, tmp2;
53 /* Initialize variables */
54 reg1 = reg2 = reg3 = 0;
56 /* Build up column parity */
57 for (i = 0; i < 256; i++) {
58 /* Get CP0 - CP5 from table */
59 idx = nand_ecc_precalc_table[*dat++];
62 /* All bit XOR = 1 ? */
65 reg2 ^= ~((uint8_t) i);
69 /* Create non-inverted ECC code from line parity */
70 tmp1 = (reg3 & 0x80) >> 0; /* B7 -> B7 */
71 tmp1 |= (reg2 & 0x80) >> 1; /* B7 -> B6 */
72 tmp1 |= (reg3 & 0x40) >> 1; /* B6 -> B5 */
73 tmp1 |= (reg2 & 0x40) >> 2; /* B6 -> B4 */
74 tmp1 |= (reg3 & 0x20) >> 2; /* B5 -> B3 */
75 tmp1 |= (reg2 & 0x20) >> 3; /* B5 -> B2 */
76 tmp1 |= (reg3 & 0x10) >> 3; /* B4 -> B1 */
77 tmp1 |= (reg2 & 0x10) >> 4; /* B4 -> B0 */
79 tmp2 = (reg3 & 0x08) << 4; /* B3 -> B7 */
80 tmp2 |= (reg2 & 0x08) << 3; /* B3 -> B6 */
81 tmp2 |= (reg3 & 0x04) << 3; /* B2 -> B5 */
82 tmp2 |= (reg2 & 0x04) << 2; /* B2 -> B4 */
83 tmp2 |= (reg3 & 0x02) << 2; /* B1 -> B3 */
84 tmp2 |= (reg2 & 0x02) << 1; /* B1 -> B2 */
85 tmp2 |= (reg3 & 0x01) << 1; /* B0 -> B1 */
86 tmp2 |= (reg2 & 0x01) << 0; /* B7 -> B0 */
88 /* Calculate final ECC code */
96 ecc_code[2] = ((~reg1) << 2) | 0x03;
101 static inline int countbits(uint32_t b)
111 * nand_correct_data - Detect and correct a 1 bit error for 256 byte block
113 int nand_correct_data(struct nand_device *nand, u_char *dat,
114 u_char *read_ecc, u_char *calc_ecc)
119 s0 = calc_ecc[0] ^ read_ecc[0];
120 s1 = calc_ecc[1] ^ read_ecc[1];
121 s2 = calc_ecc[2] ^ read_ecc[2];
123 s1 = calc_ecc[0] ^ read_ecc[0];
124 s0 = calc_ecc[1] ^ read_ecc[1];
125 s2 = calc_ecc[2] ^ read_ecc[2];
127 if ((s0 | s1 | s2) == 0)
130 /* Check for a single bit error */
131 if (((s0 ^ (s0 >> 1)) & 0x55) == 0x55 &&
132 ((s1 ^ (s1 >> 1)) & 0x55) == 0x55 &&
133 ((s2 ^ (s2 >> 1)) & 0x54) == 0x54) {
135 uint32_t byteoffs, bitnum;
137 byteoffs = (s1 << 0) & 0x80;
138 byteoffs |= (s1 << 1) & 0x40;
139 byteoffs |= (s1 << 2) & 0x20;
140 byteoffs |= (s1 << 3) & 0x10;
142 byteoffs |= (s0 >> 4) & 0x08;
143 byteoffs |= (s0 >> 3) & 0x04;
144 byteoffs |= (s0 >> 2) & 0x02;
145 byteoffs |= (s0 >> 1) & 0x01;
147 bitnum = (s2 >> 5) & 0x04;
148 bitnum |= (s2 >> 4) & 0x02;
149 bitnum |= (s2 >> 3) & 0x01;
151 dat[byteoffs] ^= (1 << bitnum);
156 if (countbits(s0 | ((uint32_t)s1 << 8) | ((uint32_t)s2 << 16)) == 1)