[PATCH] [MTD] [NAND] nand_ecc.c: adding support for 512 byte ecc
frans
fransmeulenbroeks at gmail.com
Sat Aug 23 12:18:34 EDT 2008
From: "Singh, Vimal" <vimalsingh at ti.com>
Support 512 byte ECC calculation
[FM: updated two comments]
Signed-off-by: Vimal Singh <vimalsingh at ti.com>
Signed-off-by: Frans Meulenbroeks <fransmeulenbroeks at gmail.com>
---
recreated the patch after making the changes
there are a few other minor optimisations possible, but I am planning to
rework the code and rebench for ARM (there are a few statements
like rp2 = (par ^ rp3) & 0xff; which were marginally faster on pentium
but might be less efficient on ARM and/or MIPS. As this is typically used
for embedded processors it makes sense to optimise for those targets
(especially if the effect for x86 is hardly or not noticable)
Frans.
diff --git a/drivers/mtd/nand/nand_ecc.c b/drivers/mtd/nand/nand_ecc.c
index fd19787..868147a 100644
--- a/drivers/mtd/nand/nand_ecc.c
+++ b/drivers/mtd/nand/nand_ecc.c
@@ -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>
#include <asm/byteorder.h>
#else
@@ -148,8 +150,9 @@ static const char addressbits[256] = {
};
/**
- * nand_calculate_ecc - [NAND Interface] Calculate 3-byte ECC for 256-byte block
- * @mtd: MTD block structure (unused)
+ * nand_calculate_ecc - [NAND Interface] Calculate 3-byte ECC for 256/512-byte
+ * block
+ * @mtd: MTD block structure
* @buf: input buffer with raw data
* @code: output buffer with ECC
*/
@@ -158,13 +161,18 @@ int nand_calculate_ecc(struct mtd_info *mtd, const unsigned char *buf,
{
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 make 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;
@@ -173,6 +181,7 @@ int nand_calculate_ecc(struct mtd_info *mtd, const unsigned char *buf,
rp10 = 0;
rp12 = 0;
rp14 = 0;
+ rp16 = 0;
/*
* The loop is unrolled a number of times;
@@ -181,10 +190,10 @@ int nand_calculate_ecc(struct mtd_info *mtd, const unsigned char *buf,
* 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;
@@ -247,12 +256,14 @@ int nand_calculate_ecc(struct mtd_info *mtd, const unsigned char *buf,
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);
@@ -273,6 +284,11 @@ int nand_calculate_ecc(struct mtd_info *mtd, const unsigned char *buf,
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
@@ -315,7 +331,7 @@ int nand_calculate_ecc(struct mtd_info *mtd, const unsigned char *buf,
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);
@@ -329,6 +345,8 @@ int nand_calculate_ecc(struct mtd_info *mtd, const unsigned char *buf,
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.
@@ -375,32 +393,46 @@ int nand_calculate_ecc(struct mtd_info *mtd, const unsigned char *buf,
(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);
/**
* nand_correct_data - [NAND Interface] Detect and correct bit error(s)
- * @mtd: MTD block structure (unused)
+ * @mtd: MTD block structure
* @buf: raw data read from the chip
* @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)
{
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)
@@ -426,10 +458,12 @@ int nand_correct_data(struct mtd_info *mtd, unsigned char *buf,
if ((((b0 ^ (b0 >> 1)) & 0x55) == 0x55) &&
(((b1 ^ (b1 >> 1)) & 0x55) == 0x55) &&
- (((b2 ^ (b2 >> 1)) & 0x54) == 0x54)) { /* single bit error */
+ ((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
@@ -443,7 +477,11 @@ int nand_correct_data(struct mtd_info *mtd, unsigned char *buf,
* 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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