X-Git-Url: http://git.onelab.eu/?a=blobdiff_plain;f=drivers%2Fmtd%2Fnand%2Fnand_ecc.c;h=40ac909150a3db5701c572fe536b9e1e6a5c766b;hb=9464c7cf61b9433057924c36e6e02f303a00e768;hp=dd438ca47d9ab46a1978483ffa0c5ce5b239c04a;hpb=41689045f6a3cbe0550e1d34e9cc20d2e8c432ba;p=linux-2.6.git

diff --git a/drivers/mtd/nand/nand_ecc.c b/drivers/mtd/nand/nand_ecc.c
index dd438ca47..40ac90915 100644
--- a/drivers/mtd/nand/nand_ecc.c
+++ b/drivers/mtd/nand/nand_ecc.c
@@ -7,8 +7,6 @@
  * 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
@@ -64,75 +62,90 @@ static const u_char nand_ecc_precalc_table[] = {
 	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)
@@ -143,54 +156,93 @@ static inline int countbits(uint32_t byte)
  *
  * 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");