[PATCH] [MTD] [NAND] nand_ecc.c: adding support for 512 byte ecc
Singh, Vimal
vimalsingh at ti.com
Fri Aug 22 04:45:17 EDT 2008
>On Fri, 2008-08-22 at 11:09 +0530, Singh, Vimal wrote:
>> + rp16 = 0;
> >+ rp17 = 0; /* to make cmpiler happy */
>Please, use
>
>uint32_t uninitialized_var(rp17);
>
>to avoid unnecessary initialization to 0 and avoid gcc warning as well.
Here is the patch after taking your inputs with some additional changes
in comments.
----
Thanks and Regards,
vimal singh
Signed-off-by: Vimal Singh <vimalsingh at ti.com>
---
drivers/mtd/nand/nand_ecc.c | 84 ++++++++++++++++++++++++++++++++------------
1 files changed, 62 insertions(+), 22 deletions(-)
Index: linux-omap-2.6/drivers/mtd/nand/nand_ecc.c
===================================================================
--- linux-omap-2.6.orig/drivers/mtd/nand/nand_ecc.c 2008-08-22 12:58:33.000000000 +0530
+++ linux-omap-2.6/drivers/mtd/nand/nand_ecc.c 2008-08-22 13:10:10.000000000 +0530
@@ -42,6 +42,8 @@
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/module.h>
+#include <linux/mtd/mtd.h>
+#include <linux/mtd/nand.h>
#include <linux/mtd/nand_ecc.h>
#else
#include <stdint.h>
@@ -144,7 +146,8 @@
};
/**
- * nand_calculate_ecc - [NAND Interface] Calculate 3-byte ECC for 256-byte block
+ * nand_calculate_ecc - [NAND Interface] Calculate 3-byte ECC for 256/512-byte
+ * block
* @mtd: MTD block structure (unused)
* @dat: raw data
* @ecc_code: buffer for ECC
@@ -154,13 +157,18 @@
{
int i;
const uint32_t *bp = (uint32_t *)buf;
+ /* 256 or 512 bytes/ecc */
+ const uint32_t eccsize_mult =
+ (((struct nand_chip *)mtd->priv)->ecc.size) >> 8;
uint32_t cur; /* current value in buffer */
- /* rp0..rp15 are the various accumulated parities (per byte) */
+ /* rp0..rp15..rp17 are the various accumulated parities (per byte) */
uint32_t rp0, rp1, rp2, rp3, rp4, rp5, rp6, rp7;
- uint32_t rp8, rp9, rp10, rp11, rp12, rp13, rp14, rp15;
+ uint32_t rp8, rp9, rp10, rp11, rp12, rp13, rp14, rp15, rp16;
+ uint32_t uninitialized_var(rp17); /* to keep compiler happy */
uint32_t par; /* the cumulative parity for all data */
uint32_t tmppar; /* the cumulative parity for this iteration;
- for rp12 and rp14 at the end of the loop */
+ for rp12, rp14 and rp16 at the end of the
+ loop */
par = 0;
rp4 = 0;
@@ -169,6 +177,7 @@
rp10 = 0;
rp12 = 0;
rp14 = 0;
+ rp16 = 0;
/*
* The loop is unrolled a number of times;
@@ -177,10 +186,10 @@
* Note: passing unaligned data might give a performance penalty.
* It is assumed that the buffers are aligned.
* tmppar is the cumulative sum of this iteration.
- * needed for calculating rp12, rp14 and par
+ * needed for calculating rp12, rp14, rp16 and par
* also used as a performance improvement for rp6, rp8 and rp10
*/
- for (i = 0; i < 4; i++) {
+ for (i = 0; i < eccsize_mult << 2; i++) {
cur = *bp++;
tmppar = cur;
rp4 ^= cur;
@@ -243,12 +252,14 @@
rp12 ^= tmppar;
if ((i & 0x2) == 0)
rp14 ^= tmppar;
+ if (eccsize_mult == 2 && (i & 0x4) == 0)
+ rp16 ^= tmppar;
}
/*
* handle the fact that we use longword operations
- * we'll bring rp4..rp14 back to single byte entities by shifting and
- * xoring first fold the upper and lower 16 bits,
+ * we'll bring rp4..rp14..rp16 back to single byte entities by
+ * shifting and xoring first fold the upper and lower 16 bits,
* then the upper and lower 8 bits.
*/
rp4 ^= (rp4 >> 16);
@@ -269,6 +280,11 @@
rp14 ^= (rp14 >> 16);
rp14 ^= (rp14 >> 8);
rp14 &= 0xff;
+ if (eccsize_mult == 2) {
+ rp16 ^= (rp16 >> 16);
+ rp16 ^= (rp16 >> 8);
+ rp16 &= 0xff;
+ }
/*
* we also need to calculate the row parity for rp0..rp3
@@ -297,7 +313,7 @@
par &= 0xff;
/*
- * and calculate rp5..rp15
+ * and calculate rp5..rp15..rp17
* note that par = rp4 ^ rp5 and due to the commutative property
* of the ^ operator we can say:
* rp5 = (par ^ rp4);
@@ -311,6 +327,8 @@
rp11 = (par ^ rp10) & 0xff;
rp13 = (par ^ rp12) & 0xff;
rp15 = (par ^ rp14) & 0xff;
+ if (eccsize_mult == 2)
+ rp17 = (par ^ rp16) & 0xff;
/*
* Finally calculate the ecc bits.
@@ -357,14 +375,25 @@
(invparity[rp9] << 1) |
(invparity[rp8]);
#endif
- code[2] =
- (invparity[par & 0xf0] << 7) |
- (invparity[par & 0x0f] << 6) |
- (invparity[par & 0xcc] << 5) |
- (invparity[par & 0x33] << 4) |
- (invparity[par & 0xaa] << 3) |
- (invparity[par & 0x55] << 2) |
- 3;
+ if (eccsize_mult == 1)
+ code[2] =
+ (invparity[par & 0xf0] << 7) |
+ (invparity[par & 0x0f] << 6) |
+ (invparity[par & 0xcc] << 5) |
+ (invparity[par & 0x33] << 4) |
+ (invparity[par & 0xaa] << 3) |
+ (invparity[par & 0x55] << 2) |
+ 3;
+ else
+ code[2] =
+ (invparity[par & 0xf0] << 7) |
+ (invparity[par & 0x0f] << 6) |
+ (invparity[par & 0xcc] << 5) |
+ (invparity[par & 0x33] << 4) |
+ (invparity[par & 0xaa] << 3) |
+ (invparity[par & 0x55] << 2) |
+ (invparity[rp17] << 1) |
+ (invparity[rp16] << 0);
return 0;
}
EXPORT_SYMBOL(nand_calculate_ecc);
@@ -376,7 +405,7 @@
* @read_ecc: ECC from the chip
* @calc_ecc: the ECC calculated from raw data
*
- * Detect and correct a 1 bit error for 256 byte block
+ * Detect and correct a 1 bit error for 256/512 byte block
*/
int nand_correct_data(struct mtd_info *mtd, unsigned char *buf,
unsigned char *read_ecc, unsigned char *calc_ecc)
@@ -384,6 +413,9 @@
int nr_bits;
unsigned char b0, b1, b2;
unsigned char byte_addr, bit_addr;
+ /* 256 or 512 bytes/ecc */
+ const uint32_t eccsize_mult =
+ (((struct nand_chip *)mtd->priv)->ecc.size) >> 8;
/*
* b0 to b2 indicate which bit is faulty (if any)
@@ -408,10 +440,14 @@
/* ordered in order of likelihood */
if (nr_bits == 0)
return 0; /* no error */
- if (nr_bits == 11) { /* correctable error */
+ if ((((b0 ^ (b0 >> 1)) & 0x55) == 0x55) &&
+ (((b1 ^ (b1 >> 1)) & 0x55) == 0x55) &&
+ ((eccsize_mult == 1 && ((b2 ^ (b2 >> 1)) & 0x54) == 0x54) ||
+ (eccsize_mult == 2 && ((b2 ^ (b2 >> 1)) & 0x55) == 0x55))) {
+ /* single bit error */
/*
- * rp15/13/11/9/7/5/3/1 indicate which byte is the faulty byte
- * cp 5/3/1 indicate the faulty bit.
+ * rp17/rp15/13/11/9/7/5/3/1 indicate which byte is the faulty
+ * byte, cp 5/3/1 indicate the faulty bit.
* A lookup table (called addressbits) is used to filter
* the bits from the byte they are in.
* A marginal optimisation is possible by having three
@@ -425,7 +461,11 @@
* We could also do addressbits[b2] >> 1 but for the
* performace it does not make any difference
*/
- byte_addr = (addressbits[b1] << 4) + addressbits[b0];
+ if (eccsize_mult == 1)
+ byte_addr = (addressbits[b1] << 4) + addressbits[b0];
+ else
+ byte_addr = (addressbits[b2 & 0x3] << 8) +
+ (addressbits[b1] << 4) + addressbits[b0];
bit_addr = addressbits[b2 >> 2];
/* flip the bit */
buf[byte_addr] ^= (1 << bit_addr);
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