* Copyright (C) 2000-2004 Steven J. Hill (sjhill@realitydiluted.com)
* Toshiba America Electronics Components, Inc.
*
- * Copyright (C) 2006 Thomas Gleixner <tglx@linutronix.de>
- *
* $Id: nand_ecc.c,v 1.15 2005/11/07 11:14:30 gleixner Exp $
*
* This file is free software; you can redistribute it and/or modify it
0x00, 0x55, 0x56, 0x03, 0x59, 0x0c, 0x0f, 0x5a, 0x5a, 0x0f, 0x0c, 0x59, 0x03, 0x56, 0x55, 0x00
};
+
/**
- * nand_calculate_ecc - [NAND Interface] Calculate 3-byte ECC for 256-byte block
+ * nand_trans_result - [GENERIC] create non-inverted ECC
+ * @reg2: line parity reg 2
+ * @reg3: line parity reg 3
+ * @ecc_code: ecc
+ *
+ * Creates non-inverted ECC code from line parity
+ */
+static void nand_trans_result(u_char reg2, u_char reg3,
+ u_char *ecc_code)
+{
+ u_char a, b, i, tmp1, tmp2;
+
+ /* Initialize variables */
+ a = b = 0x80;
+ tmp1 = tmp2 = 0;
+
+ /* Calculate first ECC byte */
+ for (i = 0; i < 4; i++) {
+ if (reg3 & a) /* LP15,13,11,9 --> ecc_code[0] */
+ tmp1 |= b;
+ b >>= 1;
+ if (reg2 & a) /* LP14,12,10,8 --> ecc_code[0] */
+ tmp1 |= b;
+ b >>= 1;
+ a >>= 1;
+ }
+
+ /* Calculate second ECC byte */
+ b = 0x80;
+ for (i = 0; i < 4; i++) {
+ if (reg3 & a) /* LP7,5,3,1 --> ecc_code[1] */
+ tmp2 |= b;
+ b >>= 1;
+ if (reg2 & a) /* LP6,4,2,0 --> ecc_code[1] */
+ tmp2 |= b;
+ b >>= 1;
+ a >>= 1;
+ }
+
+ /* Store two of the ECC bytes */
+ ecc_code[0] = tmp1;
+ ecc_code[1] = tmp2;
+}
+
+/**
+ * nand_calculate_ecc - [NAND Interface] Calculate 3 byte ECC code for 256 byte block
* @mtd: MTD block structure
* @dat: raw data
* @ecc_code: buffer for ECC
*/
-int nand_calculate_ecc(struct mtd_info *mtd, const u_char *dat,
- u_char *ecc_code)
+int nand_calculate_ecc(struct mtd_info *mtd, const u_char *dat, u_char *ecc_code)
{
- uint8_t idx, reg1, reg2, reg3, tmp1, tmp2;
- int i;
+ u_char idx, reg1, reg2, reg3;
+ int j;
/* Initialize variables */
reg1 = reg2 = reg3 = 0;
+ ecc_code[0] = ecc_code[1] = ecc_code[2] = 0;
/* Build up column parity */
- for(i = 0; i < 256; i++) {
+ for(j = 0; j < 256; j++) {
+
/* Get CP0 - CP5 from table */
- idx = nand_ecc_precalc_table[*dat++];
+ idx = nand_ecc_precalc_table[dat[j]];
reg1 ^= (idx & 0x3f);
/* All bit XOR = 1 ? */
if (idx & 0x40) {
- reg3 ^= (uint8_t) i;
- reg2 ^= ~((uint8_t) i);
+ reg3 ^= (u_char) j;
+ reg2 ^= ~((u_char) j);
}
}
/* 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 */
+ nand_trans_result(reg2, reg3, ecc_code);
/* Calculate final ECC code */
-#ifdef CONFIG_NAND_ECC_SMC
- ecc_code[0] = ~tmp2;
- ecc_code[1] = ~tmp1;
-#else
- ecc_code[0] = ~tmp1;
- ecc_code[1] = ~tmp2;
-#endif
+ ecc_code[0] = ~ecc_code[0];
+ ecc_code[1] = ~ecc_code[1];
ecc_code[2] = ((~reg1) << 2) | 0x03;
-
return 0;
}
-EXPORT_SYMBOL(nand_calculate_ecc);
-
-static inline int countbits(uint32_t byte)
-{
- int res = 0;
-
- for (;byte; byte >>= 1)
- res += byte & 0x01;
- return res;
-}
/**
* nand_correct_data - [NAND Interface] Detect and correct bit error(s)
*
* Detect and correct a 1 bit error for 256 byte block
*/
-int nand_correct_data(struct mtd_info *mtd, u_char *dat,
- u_char *read_ecc, u_char *calc_ecc)
+int nand_correct_data(struct mtd_info *mtd, u_char *dat, u_char *read_ecc, u_char *calc_ecc)
{
- uint8_t s0, s1, s2;
-
-#ifdef CONFIG_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;
+ u_char a, b, c, d1, d2, d3, add, bit, i;
- bitnum = (s2 >> 5) & 0x04;
- bitnum |= (s2 >> 4) & 0x02;
- bitnum |= (s2 >> 3) & 0x01;
+ /* Do error detection */
+ d1 = calc_ecc[0] ^ read_ecc[0];
+ d2 = calc_ecc[1] ^ read_ecc[1];
+ d3 = calc_ecc[2] ^ read_ecc[2];
- dat[byteoffs] ^= (1 << bitnum);
-
- return 1;
+ if ((d1 | d2 | d3) == 0) {
+ /* No errors */
+ return 0;
+ }
+ else {
+ a = (d1 ^ (d1 >> 1)) & 0x55;
+ b = (d2 ^ (d2 >> 1)) & 0x55;
+ c = (d3 ^ (d3 >> 1)) & 0x54;
+
+ /* Found and will correct single bit error in the data */
+ if ((a == 0x55) && (b == 0x55) && (c == 0x54)) {
+ c = 0x80;
+ add = 0;
+ a = 0x80;
+ for (i=0; i<4; i++) {
+ if (d1 & c)
+ add |= a;
+ c >>= 2;
+ a >>= 1;
+ }
+ c = 0x80;
+ for (i=0; i<4; i++) {
+ if (d2 & c)
+ add |= a;
+ c >>= 2;
+ a >>= 1;
+ }
+ bit = 0;
+ b = 0x04;
+ c = 0x80;
+ for (i=0; i<3; i++) {
+ if (d3 & c)
+ bit |= b;
+ c >>= 2;
+ b >>= 1;
+ }
+ b = 0x01;
+ a = dat[add];
+ a ^= (b << bit);
+ dat[add] = a;
+ return 1;
+ }
+ else {
+ i = 0;
+ while (d1) {
+ if (d1 & 0x01)
+ ++i;
+ d1 >>= 1;
+ }
+ while (d2) {
+ if (d2 & 0x01)
+ ++i;
+ d2 >>= 1;
+ }
+ while (d3) {
+ if (d3 & 0x01)
+ ++i;
+ d3 >>= 1;
+ }
+ if (i == 1) {
+ /* ECC Code Error Correction */
+ read_ecc[0] = calc_ecc[0];
+ read_ecc[1] = calc_ecc[1];
+ read_ecc[2] = calc_ecc[2];
+ return 2;
+ }
+ else {
+ /* Uncorrectable Error */
+ return -1;
+ }
+ }
}
- if(countbits(s0 | ((uint32_t)s1 << 8) | ((uint32_t)s2 <<16)) == 1)
- return 1;
-
+ /* Should never happen */
return -1;
}
+
+EXPORT_SYMBOL(nand_calculate_ecc);
EXPORT_SYMBOL(nand_correct_data);
MODULE_LICENSE("GPL");
git://git.onelab.eu / linux-2.6.git / blobdiff