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- /*
- * This file contains an ECC algorithm from Toshiba that allows for detection
- * and correction of 1-bit errors in a 256 byte block of data.
- *
- * [ Extracted from the initial code found in some early Linux versions.
- * The current Linux code is bigger while being faster, but this is of
- * no real benefit when the bottleneck largely remains the JTAG link. ]
- *
- * Copyright (C) 2000-2004 Steven J. Hill (sjhill at realitydiluted.com)
- * Toshiba America Electronics Components, Inc.
- *
- * Copyright (C) 2006 Thomas Gleixner <tglx at linutronix.de>
- *
- * This file is free software; you can redistribute it and/or modify it
- * under the terms of the GNU General Public License as published by the
- * Free Software Foundation; either version 2 or (at your option) any
- * later version.
- *
- * This file is distributed in the hope that it will be useful, but WITHOUT
- * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
- * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
- * for more details.
- *
- * You should have received a copy of the GNU General Public License along
- * with this file; if not, write to the Free Software Foundation, Inc.,
- * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
- *
- * As a special exception, if other files instantiate templates or use
- * macros or inline functions from these files, or you compile these
- * files and link them with other works to produce a work based on these
- * files, these files do not by themselves cause the resulting work to be
- * covered by the GNU General Public License. However the source code for
- * these files must still be made available in accordance with section (3)
- * of the GNU General Public License.
- *
- * This exception does not invalidate any other reasons why a work based on
- * this file might be covered by the GNU General Public License.
- */
-
- #ifdef HAVE_CONFIG_H
- #include "config.h"
- #endif
-
- #include "core.h"
-
- /*
- * Pre-calculated 256-way 1 byte column parity
- */
- 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
- };
-
- /*
- * nand_calculate_ecc - Calculate 3-byte ECC for 256-byte block
- */
- int nand_calculate_ecc(struct nand_device *nand, const uint8_t *dat, uint8_t *ecc_code)
- {
- uint8_t idx, reg1, reg2, reg3, tmp1, tmp2;
- int i;
-
- /* Initialize variables */
- reg1 = reg2 = reg3 = 0;
-
- /* Build up column parity */
- for (i = 0; i < 256; i++) {
- /* Get CP0 - CP5 from table */
- idx = nand_ecc_precalc_table[*dat++];
- reg1 ^= (idx & 0x3f);
-
- /* All bit XOR = 1 ? */
- if (idx & 0x40) {
- reg3 ^= (uint8_t) i;
- reg2 ^= ~((uint8_t) i);
- }
- }
-
- /* Create non-inverted ECC code from line parity */
- tmp1 = (reg3 & 0x80) >> 0; /* B7 -> B7 */
- tmp1 |= (reg2 & 0x80) >> 1; /* B7 -> B6 */
- tmp1 |= (reg3 & 0x40) >> 1; /* B6 -> B5 */
- tmp1 |= (reg2 & 0x40) >> 2; /* B6 -> B4 */
- tmp1 |= (reg3 & 0x20) >> 2; /* B5 -> B3 */
- tmp1 |= (reg2 & 0x20) >> 3; /* B5 -> B2 */
- tmp1 |= (reg3 & 0x10) >> 3; /* B4 -> B1 */
- tmp1 |= (reg2 & 0x10) >> 4; /* B4 -> B0 */
-
- tmp2 = (reg3 & 0x08) << 4; /* B3 -> B7 */
- tmp2 |= (reg2 & 0x08) << 3; /* B3 -> B6 */
- tmp2 |= (reg3 & 0x04) << 3; /* B2 -> B5 */
- tmp2 |= (reg2 & 0x04) << 2; /* B2 -> B4 */
- tmp2 |= (reg3 & 0x02) << 2; /* B1 -> B3 */
- tmp2 |= (reg2 & 0x02) << 1; /* B1 -> B2 */
- tmp2 |= (reg3 & 0x01) << 1; /* B0 -> B1 */
- tmp2 |= (reg2 & 0x01) << 0; /* B7 -> B0 */
-
- /* Calculate final ECC code */
- #ifdef NAND_ECC_SMC
- ecc_code[0] = ~tmp2;
- ecc_code[1] = ~tmp1;
- #else
- ecc_code[0] = ~tmp1;
- ecc_code[1] = ~tmp2;
- #endif
- ecc_code[2] = ((~reg1) << 2) | 0x03;
-
- return 0;
- }
-
- static inline int countbits(uint32_t b)
- {
- int res = 0;
-
- for (; b; b >>= 1)
- res += b & 0x01;
- return res;
- }
-
- /**
- * nand_correct_data - Detect and correct a 1 bit error for 256 byte block
- */
- int nand_correct_data(struct nand_device *nand, u_char *dat,
- u_char *read_ecc, u_char *calc_ecc)
- {
- uint8_t s0, s1, s2;
-
- #ifdef NAND_ECC_SMC
- s0 = calc_ecc[0] ^ read_ecc[0];
- s1 = calc_ecc[1] ^ read_ecc[1];
- s2 = calc_ecc[2] ^ read_ecc[2];
- #else
- s1 = calc_ecc[0] ^ read_ecc[0];
- s0 = calc_ecc[1] ^ read_ecc[1];
- s2 = calc_ecc[2] ^ read_ecc[2];
- #endif
- if ((s0 | s1 | s2) == 0)
- return 0;
-
- /* Check for a single bit error */
- if (((s0 ^ (s0 >> 1)) & 0x55) == 0x55 &&
- ((s1 ^ (s1 >> 1)) & 0x55) == 0x55 &&
- ((s2 ^ (s2 >> 1)) & 0x54) == 0x54) {
-
- uint32_t byteoffs, bitnum;
-
- byteoffs = (s1 << 0) & 0x80;
- byteoffs |= (s1 << 1) & 0x40;
- byteoffs |= (s1 << 2) & 0x20;
- byteoffs |= (s1 << 3) & 0x10;
-
- byteoffs |= (s0 >> 4) & 0x08;
- byteoffs |= (s0 >> 3) & 0x04;
- byteoffs |= (s0 >> 2) & 0x02;
- byteoffs |= (s0 >> 1) & 0x01;
-
- bitnum = (s2 >> 5) & 0x04;
- bitnum |= (s2 >> 4) & 0x02;
- bitnum |= (s2 >> 3) & 0x01;
-
- dat[byteoffs] ^= (1 << bitnum);
-
- return 1;
- }
-
- if (countbits(s0 | ((uint32_t)s1 << 8) | ((uint32_t)s2 << 16)) == 1)
- return 1;
-
- return -1;
- }
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