X-Git-Url: http://www.aleph1.co.uk/gitweb/?p=yaffs2.git;a=blobdiff_plain;f=yaffs_ecc.c;h=e95a8069a8c5bc0c754b9f41ddbc9944e0b76f98;hp=820041a2b633deeaa60029f1f43668f6fcd8a815;hb=2870702e0b0f4342857222a36ffcb21886c7f4bf;hpb=dccf947cb075996a9f2d833c55760af7d5e42be9 diff --git a/yaffs_ecc.c b/yaffs_ecc.c index 820041a..e95a806 100644 --- a/yaffs_ecc.c +++ b/yaffs_ecc.c @@ -1,306 +1,298 @@ /* - * YAFFS: Yet another FFS. A NAND-flash specific file system. + * YAFFS: Yet Another Flash File System. A NAND-flash specific file system. * - * yaffs_ecc.c: ECC generation/correction algorithms. - * - * Copyright (C) 2002 Aleph One Ltd. + * Copyright (C) 2002-2010 Aleph One Ltd. + * for Toby Churchill Ltd and Brightstar Engineering * * Created by Charles Manning * - * - * This program is free software; you can redistribute it and/or - * modify it under the terms of the GNU Lesser General Public License - * version 2.1 as published by the Free Software Foundation. + * 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 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 + * 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. - -const char *yaffs_ecc_c_version = "$Id: yaffs_ecc.c,v 1.2 2005-03-16 04:00:36 charles Exp $"; +/* 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, + 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, }; -static int yaffs_CountBits(unsigned char x) -{ - int r = 0; - while(x) - { - if(x & 1) r++; - x >>= 1; - } - return r; -} - -static int yaffs_CountBits32(unsigned x) -{ - int r = 0; - while(x) - { - if(x & 1) r++; - x >>= 1; - } - return r; -} - - -void yaffs_ECCCalculate(const unsigned char *data,unsigned char *ecc) +/* 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++) - { + + for (i = 0; i < 256; i++) { b = column_parity_table[*data++]; col_parity ^= b; - if(b & 0x01) // odd number of bits in the byte - { + 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; + 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; + 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 + /* Swap the bytes into the wrong order */ t = ecc[0]; ecc[0] = ecc[1]; ecc[1] = t; -#endif +#endif } -int yaffs_ECCCorrect(unsigned char *data, unsigned char *read_ecc, const unsigned char *test_ecc) +/* 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 + 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) - { - // no error - return 0; - } - - if( ((d0 ^ (d0 >> 1)) & 0x55) == 0x55 && + + 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 + ((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 + /* 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; + + 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; + + return 1; /* Corrected the error */ } - - if((yaffs_CountBits(d0)+yaffs_CountBits(d1)+yaffs_CountBits(d2)) == 1) - { - // Reccoverable error in ecc - + + 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; + + return 1; /* Corrected the error */ } - - // Unrecoverable error - - return -1; - -} + /* Unrecoverable error */ + return -1; +} -void yaffs_ECCCalculateOther(const unsigned char *data,unsigned nBytes, yaffs_ECCOther *eccOther) +/* + * 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 < nBytes; i++) - { + + 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 - { + if (b & 0x01) { + /* odd number of bits in the byte */ line_parity ^= i; line_parity_prime ^= ~i; } - + } - - eccOther->colParity = (col_parity >> 2) & 0x3f; - eccOther->lineParity = line_parity; - eccOther->lineParityPrime = line_parity_prime; + + ecc_other->col_parity = (col_parity >> 2) & 0x3f; + ecc_other->line_parity = line_parity; + ecc_other->line_parity_prime = line_parity_prime; } -int yaffs_ECCCorrectOther(unsigned char *data, unsigned nBytes, yaffs_ECCOther *read_ecc, const yaffs_ECCOther *test_ecc) +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 cDelta; // column parity delta - unsigned lDelta; // line parity delta - unsigned lDeltaPrime; // line parity delta + unsigned char delta_col; /* column parity delta */ + unsigned delta_line; /* line parity delta */ + unsigned delta_line_prime; /* line parity delta */ unsigned bit; - cDelta = read_ecc->colParity ^ test_ecc->colParity; - lDelta = read_ecc->lineParity ^ test_ecc->lineParity; - lDeltaPrime = read_ecc->lineParityPrime ^ test_ecc->lineParityPrime; - - if((cDelta | lDelta | lDeltaPrime) == 0) - { - // no error - return 0; - } - - if( lDelta == ~lDeltaPrime && - (((cDelta ^ (cDelta >> 1)) & 0x15) == 0x15)) // Not correct - { - // Single bit (recoverable) error in data + 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 0 - unsigned byte; - unsigned bit; -#endif + 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 */ -#ifdef CONFIG_YAFFS_ECC_WRONG_ORDER - // swap the bytes to correct for the wrong order - unsigned char t; - -#if 0 // NCB - t = d0; - d0 = d1; - d1 = t; -#else - t = cDelta; - cDelta = lDelta; - lDelta = t; -#endif -#endif - bit = 0; - if(cDelta & 0x20) bit |= 0x04; - if(cDelta & 0x08) bit |= 0x02; - if(cDelta & 0x02) bit |= 0x01; + if (delta_col & 0x20) + bit |= 0x04; + if (delta_col & 0x08) + bit |= 0x02; + if (delta_col & 0x02) + bit |= 0x01; - data[lDelta] ^= (1 << bit); - - return 1; - } - - if((yaffs_CountBits32(lDelta) + yaffs_CountBits32(lDeltaPrime) + yaffs_CountBits(cDelta)) == 1) - { - // Reccoverable error in ecc - - *read_ecc = *test_ecc; - return 1; + if (delta_line >= n_bytes) + return -1; + + data[delta_line] ^= (1 << bit); + + return 1; /* corrected */ } - - // Unrecoverable error - - return -1; - -} + 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; +}