NAND: Update nand_ecc.c to latest Linux version

This patch updates the nand_ecc code to the latest Linux version.
The main reason for this is the more compact code. This makes
it possible to include the ECC code into the NAND bootloader
image (NAND_SPL) for PPC4xx.

Signed-off-by: Stefan Roese <sr@denx.de>

drivers/nand/nand_ecc.c

@@ -40,6 +40,13 @@
 #if (CONFIG_COMMANDS & CFG_CMD_NAND) && !defined(CFG_NAND_LEGACY)
 
 #include<linux/mtd/mtd.h>
+
+/*
+ * NAND-SPL has no sofware ECC for now, so don't include nand_calculate_ecc(),
+ * only nand_correct_data() is needed
+ */
+
+#ifndef CONFIG_NAND_SPL
 /*
  * Pre-calculated 256-way 1 byte column parity
  */
@@ -62,90 +69,75 @@ 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_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
+ * nand_calculate_ecc - [NAND Interface] Calculate 3-byte ECC 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)
 {
-	u_char idx, reg1, reg2, reg3;
-	int j;
+	uint8_t idx, reg1, reg2, reg3, tmp1, tmp2;
+	int i;
 
 	/* Initialize variables */
 	reg1 = reg2 = reg3 = 0;
-	ecc_code[0] = ecc_code[1] = ecc_code[2] = 0;
 
 	/* Build up column parity */
-	for(j = 0; j < 256; j++) {
-
+	for(i = 0; i < 256; i++) {
 		/* Get CP0 - CP5 from table */
-		idx = nand_ecc_precalc_table[dat[j]];
+		idx = nand_ecc_precalc_table[*dat++];
 		reg1 ^= (idx & 0x3f);
 
 		/* All bit XOR = 1 ? */
 		if (idx & 0x40) {
-			reg3 ^= (u_char) j;
-			reg2 ^= ~((u_char) j);
+			reg3 ^= (uint8_t) i;
+			reg2 ^= ~((uint8_t) i);
 		}
 	}
 
 	/* Create non-inverted ECC code from line parity */
-	nand_trans_result(reg2, reg3, ecc_code);
+	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 */
 
 	/* Calculate final ECC code */
-	ecc_code[0] = ~ecc_code[0];
-	ecc_code[1] = ~ecc_code[1];
+#ifdef CONFIG_MTD_NAND_ECC_SMC
+	ecc_code[0] = ~tmp2;
+	ecc_code[1] = ~tmp1;
+#else
+	ecc_code[0] = ~tmp1;
+	ecc_code[1] = ~tmp2;
+#endif
 	ecc_code[2] = ((~reg1) << 2) | 0x03;
+
 	return 0;
 }
+#endif /* CONFIG_NAND_SPL */
+
+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)
@@ -156,88 +148,52 @@ int nand_calculate_ecc(struct mtd_info *mtd, const u_char *dat, u_char *ecc_code
  *
  * 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)
 {
-	u_char a, b, c, d1, d2, d3, add, bit, i;
+	uint8_t s0, s1, s2;
+
+#ifdef CONFIG_MTD_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;
 
-	/* Do error detection */
-	d1 = calc_ecc[0] ^ read_ecc[0];
-	d2 = calc_ecc[1] ^ read_ecc[1];
-	d3 = calc_ecc[2] ^ read_ecc[2];
+	/* Check for a single bit error */
+	if( ((s0 ^ (s0 >> 1)) & 0x55) == 0x55 &&
+	    ((s1 ^ (s1 >> 1)) & 0x55) == 0x55 &&
+	    ((s2 ^ (s2 >> 1)) & 0x54) == 0x54) {
 
-	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;
-			}
-		}
+		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;
+
+		bitnum = (s2 >> 5) & 0x04;
+		bitnum |= (s2 >> 4) & 0x02;
+		bitnum |= (s2 >> 3) & 0x01;
+
+		dat[byteoffs] ^= (1 << bitnum);
+
+		return 1;
 	}
 
-	/* Should never happen */
+	if(countbits(s0 | ((uint32_t)s1 << 8) | ((uint32_t)s2 <<16)) == 1)
+		return 1;
+
 	return -1;
 }