X-Git-Url: http://www.aleph1.co.uk/gitweb/?p=yaffs2.git;a=blobdiff_plain;f=yaffs_ecc.c;fp=yaffs_ecc.c;h=5cb49b416d90933513592aff8dfa8b6802bb9446;hp=58d0f604ba61895e1828f3b0675598c38e88d5a4;hb=68f0159122cfb94e6912dd99d6398ba72e578a72;hpb=9625e7b16224f286bb177324f2c1283b9db08286 diff --git a/yaffs_ecc.c b/yaffs_ecc.c index 58d0f60..5cb49b4 100644 --- a/yaffs_ecc.c +++ b/yaffs_ecc.c @@ -12,16 +12,16 @@ * modify it under the terms of the GNU Lesser General Public License * version 2.1 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. - * - */ + * 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' @@ -29,100 +29,130 @@ // 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 1.4 2005-07-31 00:28:04 charles Exp $"; +const char *yaffs_ecc_c_version = + "$Id: yaffs_ecc.c,v 1.5 2005-08-11 00:34:14 charles Exp $"; #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++; + while (x) { + if (x & 1) + r++; x >>= 1; } return r; } -static int yaffs_CountBits32(unsigned x) +static int yaffs_CountBits32(unsigned x) { int r = 0; - while(x) - { - if(x & 1) r++; + while (x) { + if (x & 1) + r++; x >>= 1; } return r; } - -void yaffs_ECCCalculate(const unsigned char *data,unsigned char *ecc) +void yaffs_ECCCalculate(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 @@ -130,29 +160,26 @@ void yaffs_ECCCalculate(const unsigned char *data,unsigned char *ecc) 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) +int yaffs_ECCCorrect(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) - { + + if ((d0 | d1 | d2) == 0) { // no error return 0; } - - if( ((d0 ^ (d0 >> 1)) & 0x55) == 0x55 && + + if (((d0 ^ (d0 >> 1)) & 0x55) == 0x55 && ((d1 ^ (d1 >> 1)) & 0x55) == 0x55 && - ((d2 ^ (d2 >> 1)) & 0x54) == 0x54) - { + ((d2 ^ (d2 >> 1)) & 0x54) == 0x54) { // Single bit (recoverable) error in data unsigned byte; @@ -161,127 +188,131 @@ int yaffs_ECCCorrect(unsigned char *data, unsigned char *read_ecc, const unsigne #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; + + 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; } - - if((yaffs_CountBits(d0)+yaffs_CountBits(d1)+yaffs_CountBits(d2)) == 1) - { + + if ((yaffs_CountBits(d0) + yaffs_CountBits(d1) + yaffs_CountBits(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; } - // Unrecoverable error - + return -1; - } - - -void yaffs_ECCCalculateOther(const unsigned char *data,unsigned nBytes, yaffs_ECCOther *eccOther) +void yaffs_ECCCalculateOther(const unsigned char *data, unsigned nBytes, + yaffs_ECCOther * eccOther) { 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 < nBytes; 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; } -int yaffs_ECCCorrectOther(unsigned char *data, unsigned nBytes, yaffs_ECCOther *read_ecc, const yaffs_ECCOther *test_ecc) +int yaffs_ECCCorrectOther(unsigned char *data, unsigned nBytes, + yaffs_ECCOther * read_ecc, + const yaffs_ECCOther * test_ecc) { - unsigned char cDelta; // column parity delta - unsigned lDelta; // line parity delta - unsigned lDeltaPrime; // line parity delta + unsigned char cDelta; // column parity delta + unsigned lDelta; // line parity delta + unsigned lDeltaPrime; // line parity delta unsigned bit; cDelta = read_ecc->colParity ^ test_ecc->colParity; - lDelta = read_ecc->lineParity ^ test_ecc->lineParity; + lDelta = read_ecc->lineParity ^ test_ecc->lineParity; lDeltaPrime = read_ecc->lineParityPrime ^ test_ecc->lineParityPrime; - - if((cDelta | lDelta | lDeltaPrime) == 0) - { + + if ((cDelta | lDelta | lDeltaPrime) == 0) { // no error return 0; } - - if( lDelta == ~lDeltaPrime && - (((cDelta ^ (cDelta >> 1)) & 0x15) == 0x15)) // Not correct + + if (lDelta == ~lDeltaPrime && (((cDelta ^ (cDelta >> 1)) & 0x15) == 0x15)) // Not correct { // Single bit (recoverable) error in data bit = 0; - if(cDelta & 0x20) bit |= 0x04; - if(cDelta & 0x08) bit |= 0x02; - if(cDelta & 0x02) bit |= 0x01; + if (cDelta & 0x20) + bit |= 0x04; + if (cDelta & 0x08) + bit |= 0x02; + if (cDelta & 0x02) + bit |= 0x01; data[lDelta] ^= (1 << bit); - + return 1; } - - if((yaffs_CountBits32(lDelta) + yaffs_CountBits32(lDeltaPrime) + yaffs_CountBits(cDelta)) == 1) - { + + if ((yaffs_CountBits32(lDelta) + yaffs_CountBits32(lDeltaPrime) + + yaffs_CountBits(cDelta)) == 1) { // Reccoverable error in ecc - - *read_ecc = *test_ecc; + + *read_ecc = *test_ecc; return 1; } - // Unrecoverable error - + return -1; - } - - -