*
* 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)
{
unsigned int i;
-
unsigned char col_parity = 0;
unsigned char line_parity = 0;
unsigned char line_parity_prime = 0;
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;
}
#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 */
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 &&
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 */
}
-
/*
* ECCxxxOther does ECC calcs on arbitrary n bytes of data
*/
-void yaffs_ecc_calc_other(const unsigned char *data, unsigned nBytes,
- yaffs_ECCOther *eccOther)
+void yaffs_ecc_calc_other(const unsigned char *data, unsigned n_bytes,
+ struct yaffs_ecc_other *ecc_other)
{
unsigned int i;
-
unsigned char col_parity = 0;
unsigned line_parity = 0;
unsigned line_parity_prime = 0;
unsigned char b;
- for (i = 0; i < nBytes; i++) {
+ for (i = 0; i < n_bytes; i++) {
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;
}
- eccOther->colParity = (col_parity >> 2) & 0x3f;
- eccOther->lineParity = line_parity;
- eccOther->lineParityPrime = line_parity_prime;
+ ecc_other->col_parity = (col_parity >> 2) & 0x3f;
+ ecc_other->line_parity = line_parity;
+ ecc_other->line_parity_prime = line_parity_prime;
}
-int yaffs_ecc_correct_other(unsigned char *data, unsigned nBytes,
- yaffs_ECCOther *read_ecc,
- const yaffs_ECCOther *test_ecc)
+int yaffs_ecc_correct_other(unsigned char *data, unsigned n_bytes,
+ struct yaffs_ecc_other *read_ecc,
+ const struct yaffs_ecc_other *test_ecc)
{
- unsigned char cDelta; /* column parity delta */
- unsigned lDelta; /* line parity delta */
- unsigned lDeltaPrime; /* line parity delta */
+ unsigned char delta_col; /* column parity delta */
+ unsigned delta_line; /* line parity delta */
+ unsigned delta_line_prime; /* line parity delta */
unsigned bit;
- cDelta = read_ecc->colParity ^ test_ecc->colParity;
- lDelta = read_ecc->lineParity ^ test_ecc->lineParity;
- lDeltaPrime = read_ecc->lineParityPrime ^ test_ecc->lineParityPrime;
+ 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;
- if ((cDelta | lDelta | lDeltaPrime) == 0)
- return 0; /* no error */
+ if ((delta_col | delta_line | delta_line_prime) == 0)
+ return 0; /* no error */
- if (lDelta == ~lDeltaPrime &&
- (((cDelta ^ (cDelta >> 1)) & 0x15) == 0x15)) {
+ if (delta_line == ~delta_line_prime &&
+ (((delta_col ^ (delta_col >> 1)) & 0x15) == 0x15)) {
/* Single bit (recoverable) error in data */
bit = 0;
- if (cDelta & 0x20)
+ if (delta_col & 0x20)
bit |= 0x04;
- if (cDelta & 0x08)
+ if (delta_col & 0x08)
bit |= 0x02;
- if (cDelta & 0x02)
+ if (delta_col & 0x02)
bit |= 0x01;
- if (lDelta >= nBytes)
+ if (delta_line >= n_bytes)
return -1;
- data[lDelta] ^= (1 << bit);
+ data[delta_line] ^= (1 << bit);
- return 1; /* corrected */
+ return 1; /* corrected */
}
- if ((yaffs_count_bits32(lDelta) + yaffs_count_bits32(lDeltaPrime) +
- yaffs_count_bits(cDelta)) == 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 */
projects / yaffs2.git / blobdiff