297 lines
7.2 KiB
C
297 lines
7.2 KiB
C
/*
|
|
* 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;
|
|
}
|