/*
* 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>
*
* 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,
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;
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 */
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)
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];
struct yaffs_ecc_other *ecc_other)
{
unsigned int i;
-
unsigned char col_parity = 0;
unsigned line_parity = 0;
unsigned line_parity_prime = 0;
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;