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-rw-r--r--fs/yaffs2/yaffs_ecc.c298
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diff --git a/fs/yaffs2/yaffs_ecc.c b/fs/yaffs2/yaffs_ecc.c
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-/*
- * YAFFS: Yet Another Flash File System. A NAND-flash specific file system.
- *
- * Copyright (C) 2002-2010 Aleph One Ltd.
- * for Toby Churchill Ltd and Brightstar Engineering
- *
- * Created by Charles Manning <charles@aleph1.co.uk>
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2 as
- * published by the Free Software Foundation.
- */
-
-/*
- * This code implements the ECC algorithm used in SmartMedia.
- *
- * The ECC comprises 22 bits of parity information and is stuffed into 3 bytes.
- * The two unused bit are set to 1.
- * The ECC can correct single bit errors in a 256-byte page of data. Thus, two such ECC
- * blocks are used on a 512-byte NAND page.
- *
- */
-
-/* Table generated by gen-ecc.c
- * Using a table means we do not have to calculate p1..p4 and p1'..p4'
- * for each byte of data. These are instead provided in a table in bits7..2.
- * Bit 0 of each entry indicates whether the entry has an odd or even parity, and therefore
- * this bytes influence on the line parity.
- */
-
-#include "yportenv.h"
-
-#include "yaffs_ecc.h"
-
-static const unsigned char column_parity_table[] = {
- 0x00, 0x55, 0x59, 0x0c, 0x65, 0x30, 0x3c, 0x69,
- 0x69, 0x3c, 0x30, 0x65, 0x0c, 0x59, 0x55, 0x00,
- 0x95, 0xc0, 0xcc, 0x99, 0xf0, 0xa5, 0xa9, 0xfc,
- 0xfc, 0xa9, 0xa5, 0xf0, 0x99, 0xcc, 0xc0, 0x95,
- 0x99, 0xcc, 0xc0, 0x95, 0xfc, 0xa9, 0xa5, 0xf0,
- 0xf0, 0xa5, 0xa9, 0xfc, 0x95, 0xc0, 0xcc, 0x99,
- 0x0c, 0x59, 0x55, 0x00, 0x69, 0x3c, 0x30, 0x65,
- 0x65, 0x30, 0x3c, 0x69, 0x00, 0x55, 0x59, 0x0c,
- 0xa5, 0xf0, 0xfc, 0xa9, 0xc0, 0x95, 0x99, 0xcc,
- 0xcc, 0x99, 0x95, 0xc0, 0xa9, 0xfc, 0xf0, 0xa5,
- 0x30, 0x65, 0x69, 0x3c, 0x55, 0x00, 0x0c, 0x59,
- 0x59, 0x0c, 0x00, 0x55, 0x3c, 0x69, 0x65, 0x30,
- 0x3c, 0x69, 0x65, 0x30, 0x59, 0x0c, 0x00, 0x55,
- 0x55, 0x00, 0x0c, 0x59, 0x30, 0x65, 0x69, 0x3c,
- 0xa9, 0xfc, 0xf0, 0xa5, 0xcc, 0x99, 0x95, 0xc0,
- 0xc0, 0x95, 0x99, 0xcc, 0xa5, 0xf0, 0xfc, 0xa9,
- 0xa9, 0xfc, 0xf0, 0xa5, 0xcc, 0x99, 0x95, 0xc0,
- 0xc0, 0x95, 0x99, 0xcc, 0xa5, 0xf0, 0xfc, 0xa9,
- 0x3c, 0x69, 0x65, 0x30, 0x59, 0x0c, 0x00, 0x55,
- 0x55, 0x00, 0x0c, 0x59, 0x30, 0x65, 0x69, 0x3c,
- 0x30, 0x65, 0x69, 0x3c, 0x55, 0x00, 0x0c, 0x59,
- 0x59, 0x0c, 0x00, 0x55, 0x3c, 0x69, 0x65, 0x30,
- 0xa5, 0xf0, 0xfc, 0xa9, 0xc0, 0x95, 0x99, 0xcc,
- 0xcc, 0x99, 0x95, 0xc0, 0xa9, 0xfc, 0xf0, 0xa5,
- 0x0c, 0x59, 0x55, 0x00, 0x69, 0x3c, 0x30, 0x65,
- 0x65, 0x30, 0x3c, 0x69, 0x00, 0x55, 0x59, 0x0c,
- 0x99, 0xcc, 0xc0, 0x95, 0xfc, 0xa9, 0xa5, 0xf0,
- 0xf0, 0xa5, 0xa9, 0xfc, 0x95, 0xc0, 0xcc, 0x99,
- 0x95, 0xc0, 0xcc, 0x99, 0xf0, 0xa5, 0xa9, 0xfc,
- 0xfc, 0xa9, 0xa5, 0xf0, 0x99, 0xcc, 0xc0, 0x95,
- 0x00, 0x55, 0x59, 0x0c, 0x65, 0x30, 0x3c, 0x69,
- 0x69, 0x3c, 0x30, 0x65, 0x0c, 0x59, 0x55, 0x00,
-};
-
-
-/* Calculate the ECC for a 256-byte block of data */
-void yaffs_ecc_cacl(const unsigned char *data, unsigned char *ecc)
-{
- unsigned int i;
-
- unsigned char col_parity = 0;
- unsigned char line_parity = 0;
- unsigned char line_parity_prime = 0;
- unsigned char t;
- unsigned char b;
-
- for (i = 0; i < 256; i++) {
- b = column_parity_table[*data++];
- col_parity ^= b;
-
- if (b & 0x01) { /* odd number of bits in the byte */
- line_parity ^= i;
- line_parity_prime ^= ~i;
- }
- }
-
- ecc[2] = (~col_parity) | 0x03;
-
- t = 0;
- if (line_parity & 0x80)
- t |= 0x80;
- if (line_parity_prime & 0x80)
- t |= 0x40;
- if (line_parity & 0x40)
- t |= 0x20;
- if (line_parity_prime & 0x40)
- t |= 0x10;
- if (line_parity & 0x20)
- t |= 0x08;
- if (line_parity_prime & 0x20)
- t |= 0x04;
- if (line_parity & 0x10)
- t |= 0x02;
- if (line_parity_prime & 0x10)
- t |= 0x01;
- ecc[1] = ~t;
-
- t = 0;
- if (line_parity & 0x08)
- t |= 0x80;
- if (line_parity_prime & 0x08)
- t |= 0x40;
- if (line_parity & 0x04)
- t |= 0x20;
- if (line_parity_prime & 0x04)
- t |= 0x10;
- if (line_parity & 0x02)
- t |= 0x08;
- if (line_parity_prime & 0x02)
- t |= 0x04;
- if (line_parity & 0x01)
- t |= 0x02;
- if (line_parity_prime & 0x01)
- t |= 0x01;
- ecc[0] = ~t;
-
-#ifdef CONFIG_YAFFS_ECC_WRONG_ORDER
- /* Swap the bytes into the wrong order */
- t = ecc[0];
- ecc[0] = ecc[1];
- ecc[1] = t;
-#endif
-}
-
-/* Correct the ECC on a 256 byte block of data */
-
-int yaffs_ecc_correct(unsigned char *data, unsigned char *read_ecc,
- const unsigned char *test_ecc)
-{
- unsigned char d0, d1, d2; /* deltas */
-
- d0 = read_ecc[0] ^ test_ecc[0];
- d1 = read_ecc[1] ^ test_ecc[1];
- d2 = read_ecc[2] ^ test_ecc[2];
-
- if ((d0 | d1 | d2) == 0)
- return 0; /* no error */
-
- if (((d0 ^ (d0 >> 1)) & 0x55) == 0x55 &&
- ((d1 ^ (d1 >> 1)) & 0x55) == 0x55 &&
- ((d2 ^ (d2 >> 1)) & 0x54) == 0x54) {
- /* Single bit (recoverable) error in data */
-
- unsigned byte;
- unsigned bit;
-
-#ifdef CONFIG_YAFFS_ECC_WRONG_ORDER
- /* swap the bytes to correct for the wrong order */
- unsigned char t;
-
- t = d0;
- d0 = d1;
- d1 = t;
-#endif
-
- bit = byte = 0;
-
- if (d1 & 0x80)
- byte |= 0x80;
- if (d1 & 0x20)
- byte |= 0x40;
- if (d1 & 0x08)
- byte |= 0x20;
- if (d1 & 0x02)
- byte |= 0x10;
- if (d0 & 0x80)
- byte |= 0x08;
- if (d0 & 0x20)
- byte |= 0x04;
- if (d0 & 0x08)
- byte |= 0x02;
- if (d0 & 0x02)
- byte |= 0x01;
-
- if (d2 & 0x80)
- bit |= 0x04;
- if (d2 & 0x20)
- bit |= 0x02;
- if (d2 & 0x08)
- bit |= 0x01;
-
- data[byte] ^= (1 << bit);
-
- return 1; /* Corrected the error */
- }
-
- if ((hweight8(d0) + hweight8(d1) + hweight8(d2)) == 1) {
- /* Reccoverable error in ecc */
-
- read_ecc[0] = test_ecc[0];
- read_ecc[1] = test_ecc[1];
- read_ecc[2] = test_ecc[2];
-
- return 1; /* Corrected the error */
- }
-
- /* Unrecoverable error */
-
- return -1;
-
-}
-
-/*
- * ECCxxxOther does ECC calcs on arbitrary n bytes of data
- */
-void yaffs_ecc_calc_other(const unsigned char *data, unsigned n_bytes,
- struct yaffs_ecc_other *ecc_other)
-{
- unsigned int i;
-
- unsigned char col_parity = 0;
- unsigned line_parity = 0;
- unsigned line_parity_prime = 0;
- unsigned char b;
-
- for (i = 0; i < n_bytes; i++) {
- b = column_parity_table[*data++];
- col_parity ^= b;
-
- if (b & 0x01) {
- /* odd number of bits in the byte */
- line_parity ^= i;
- line_parity_prime ^= ~i;
- }
-
- }
-
- ecc_other->col_parity = (col_parity >> 2) & 0x3f;
- ecc_other->line_parity = line_parity;
- ecc_other->line_parity_prime = line_parity_prime;
-}
-
-int yaffs_ecc_correct_other(unsigned char *data, unsigned n_bytes,
- struct yaffs_ecc_other *read_ecc,
- const struct yaffs_ecc_other *test_ecc)
-{
- unsigned char delta_col; /* column parity delta */
- unsigned delta_line; /* line parity delta */
- unsigned delta_line_prime; /* line parity delta */
- unsigned bit;
-
- delta_col = read_ecc->col_parity ^ test_ecc->col_parity;
- delta_line = read_ecc->line_parity ^ test_ecc->line_parity;
- delta_line_prime =
- read_ecc->line_parity_prime ^ test_ecc->line_parity_prime;
-
- if ((delta_col | delta_line | delta_line_prime) == 0)
- return 0; /* no error */
-
- if (delta_line == ~delta_line_prime &&
- (((delta_col ^ (delta_col >> 1)) & 0x15) == 0x15)) {
- /* Single bit (recoverable) error in data */
-
- bit = 0;
-
- if (delta_col & 0x20)
- bit |= 0x04;
- if (delta_col & 0x08)
- bit |= 0x02;
- if (delta_col & 0x02)
- bit |= 0x01;
-
- if (delta_line >= n_bytes)
- return -1;
-
- data[delta_line] ^= (1 << bit);
-
- return 1; /* corrected */
- }
-
- if ((hweight32(delta_line) +
- hweight32(delta_line_prime) +
- hweight8(delta_col)) == 1) {
- /* Reccoverable error in ecc */
-
- *read_ecc = *test_ecc;
- return 1; /* corrected */
- }
-
- /* Unrecoverable error */
-
- return -1;
-}