X-Git-Url: http://www.aleph1.co.uk/gitweb/?p=yaffs2.git;a=blobdiff_plain;f=yaffs_ecc.c;h=9294107c150d261bbb6c90c8c78b6590ba4b97a4;hp=290f8d34644242f53a66d997b57f9e93167633ca;hb=18a85b88ac3ad344bbc8f2530c84e2a621d901c4;hpb=757a553001be4016e9c5d8880648d3703f34b10e

diff --git a/yaffs_ecc.c b/yaffs_ecc.c
index 290f8d3..9294107 100644
--- a/yaffs_ecc.c
+++ b/yaffs_ecc.c
@@ -1,7 +1,7 @@
 /*
  * YAFFS: Yet Another Flash File System. A NAND-flash specific file system.
  *
- * Copyright (C) 2002-2010 Aleph One Ltd.
+ * Copyright (C) 2002-2011 Aleph One Ltd.
  *   for Toby Churchill Ltd and Brightstar Engineering
  *
  * Created by Charles Manning <charles@aleph1.co.uk>
@@ -16,22 +16,22 @@
  *
  * 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.
+ * 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.
  *
  */
 
+#include "yportenv.h"
+
+#include "yaffs_ecc.h"
+
 /* 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.
+ * 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,
@@ -67,35 +67,11 @@ static const unsigned char column_parity_table[] = {
 	0x69, 0x3c, 0x30, 0x65, 0x0c, 0x59, 0x55, 0x00,
 };
 
-/* Count the bits in an unsigned char or a U32 */
-
-static int yaffs_count_bits(unsigned char x)
-{
-	int r = 0;
-	while (x) {
-		if (x & 1)
-			r++;
-		x >>= 1;
-	}
-	return r;
-}
-
-static int yaffs_count_bits32(unsigned x)
-{
-	int r = 0;
-	while (x) {
-		if (x & 1)
-			r++;
-		x >>= 1;
-	}
-	return r;
-}
 
 /* Calculate the ECC for a 256-byte block of data */
-void yaffs_ecc_cacl(const unsigned char *data, unsigned char *ecc)
+void yaffs_ecc_calc(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;
@@ -106,7 +82,7 @@ void yaffs_ecc_cacl(const unsigned char *data, unsigned char *ecc)
 		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;
 		}
@@ -152,19 +128,12 @@ void yaffs_ecc_cacl(const unsigned char *data, unsigned char *ecc)
 		t |= 0x01;
 	ecc[0] = ~t;
 
-#ifdef CONFIG_YAFFS_ECC_WRONG_ORDER
-	/* Swap the bytes into the wrong order */
-	t = ecc[0];
-	ecc[0] = ecc[1];
-	ecc[1] = t;
-#endif
 }
 
-
 /* 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)
+		      const unsigned char *test_ecc)
 {
 	unsigned char d0, d1, d2;	/* deltas */
 
@@ -173,7 +142,7 @@ int yaffs_ecc_correct(unsigned char *data, unsigned char *read_ecc,
 	d2 = read_ecc[2] ^ test_ecc[2];
 
 	if ((d0 | d1 | d2) == 0)
-		return 0; /* no error */
+		return 0;	/* no error */
 
 	if (((d0 ^ (d0 >> 1)) & 0x55) == 0x55 &&
 	    ((d1 ^ (d1 >> 1)) & 0x55) == 0x55 &&
@@ -183,15 +152,6 @@ int yaffs_ecc_correct(unsigned char *data, unsigned char *read_ecc,
 		unsigned byte;
 		unsigned bit;
 
-#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)
@@ -220,19 +180,17 @@ int yaffs_ecc_correct(unsigned char *data, unsigned char *read_ecc,
 
 		data[byte] ^= (1 << bit);
 
-		return 1; /* Corrected the error */
+		return 1;	/* Corrected the error */
 	}
 
-	if ((yaffs_count_bits(d0) +
-	     yaffs_count_bits(d1) +
-	     yaffs_count_bits(d2)) ==  1) {
+	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; /* Corrected the error */
+		return 1;	/* Corrected the error */
 	}
 
 	/* Unrecoverable error */
@@ -241,15 +199,13 @@ int yaffs_ecc_correct(unsigned char *data, unsigned char *read_ecc,
 
 }
 
-
 /*
  * 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)
+			  struct yaffs_ecc_other *ecc_other)
 {
 	unsigned int i;
-
 	unsigned char col_parity = 0;
 	unsigned line_parity = 0;
 	unsigned line_parity_prime = 0;
@@ -259,7 +215,7 @@ void yaffs_ecc_calc_other(const unsigned char *data, unsigned n_bytes,
 		b = column_parity_table[*data++];
 		col_parity ^= b;
 
-		if (b & 0x01)	 {
+		if (b & 0x01) {
 			/* odd number of bits in the byte */
 			line_parity ^= i;
 			line_parity_prime ^= ~i;
@@ -273,8 +229,8 @@ void yaffs_ecc_calc_other(const unsigned char *data, unsigned n_bytes,
 }
 
 int yaffs_ecc_correct_other(unsigned char *data, unsigned n_bytes,
-			struct yaffs_ecc_other *read_ecc,
-			const struct yaffs_ecc_other *test_ecc)
+			    struct yaffs_ecc_other *read_ecc,
+			    const struct yaffs_ecc_other *test_ecc)
 {
 	unsigned char delta_col;	/* column parity delta */
 	unsigned delta_line;	/* line parity delta */
@@ -283,10 +239,11 @@ int yaffs_ecc_correct_other(unsigned char *data, unsigned n_bytes,
 
 	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;
+	delta_line_prime =
+	    read_ecc->line_parity_prime ^ test_ecc->line_parity_prime;
 
 	if ((delta_col | delta_line | delta_line_prime) == 0)
-		return 0; /* no error */
+		return 0;	/* no error */
 
 	if (delta_line == ~delta_line_prime &&
 	    (((delta_col ^ (delta_col >> 1)) & 0x15) == 0x15)) {
@@ -306,15 +263,16 @@ int yaffs_ecc_correct_other(unsigned char *data, unsigned n_bytes,
 
 		data[delta_line] ^= (1 << bit);
 
-		return 1; /* corrected */
+		return 1;	/* corrected */
 	}
 
-	if ((yaffs_count_bits32(delta_line) + yaffs_count_bits32(delta_line_prime) +
-			yaffs_count_bits(delta_col)) == 1) {
+	if ((hweight32(delta_line) +
+	     hweight32(delta_line_prime) +
+	     hweight8(delta_col)) == 1) {
 		/* Reccoverable error in ecc */
 
 		*read_ecc = *test_ecc;
-		return 1; /* corrected */
+		return 1;	/* corrected */
 	}
 
 	/* Unrecoverable error */