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[MTD] [NAND] nand_ecc.c: adding support for 512 byte ecc
Support 512 byte ECC calculation [FM: updated two comments] Signed-off-by: Vimal Singh <vimalsingh@ti.com> Signed-off-by: Frans Meulenbroeks <fransmeulenbroeks@gmail.com> Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
This commit is contained in:
Singh, Vimal
David Woodhouse
parent
dffc8d6654
commit
d68156cfad
@ -42,6 +42,8 @@
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#include <linux/types.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/mtd/mtd.h>
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#include <linux/mtd/nand.h>
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#include <linux/mtd/nand_ecc.h>
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#include <asm/byteorder.h>
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#else
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@ -148,8 +150,9 @@ static const char addressbits[256] = {
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};
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/**
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* nand_calculate_ecc - [NAND Interface] Calculate 3-byte ECC for 256-byte block
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* @mtd: MTD block structure (unused)
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* nand_calculate_ecc - [NAND Interface] Calculate 3-byte ECC for 256/512-byte
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* block
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* @mtd: MTD block structure
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* @buf: input buffer with raw data
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* @code: output buffer with ECC
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*/
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@ -158,13 +161,18 @@ int nand_calculate_ecc(struct mtd_info *mtd, const unsigned char *buf,
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{
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int i;
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const uint32_t *bp = (uint32_t *)buf;
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/* 256 or 512 bytes/ecc */
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const uint32_t eccsize_mult =
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(((struct nand_chip *)mtd->priv)->ecc.size) >> 8;
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uint32_t cur; /* current value in buffer */
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/* rp0..rp15 are the various accumulated parities (per byte) */
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/* rp0..rp15..rp17 are the various accumulated parities (per byte) */
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uint32_t rp0, rp1, rp2, rp3, rp4, rp5, rp6, rp7;
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uint32_t rp8, rp9, rp10, rp11, rp12, rp13, rp14, rp15;
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uint32_t rp8, rp9, rp10, rp11, rp12, rp13, rp14, rp15, rp16;
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uint32_t uninitialized_var(rp17); /* to make compiler happy */
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uint32_t par; /* the cumulative parity for all data */
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uint32_t tmppar; /* the cumulative parity for this iteration;
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for rp12 and rp14 at the end of the loop */
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for rp12, rp14 and rp16 at the end of the
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loop */
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par = 0;
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rp4 = 0;
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@ -173,6 +181,7 @@ int nand_calculate_ecc(struct mtd_info *mtd, const unsigned char *buf,
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rp10 = 0;
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rp12 = 0;
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rp14 = 0;
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rp16 = 0;
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/*
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* The loop is unrolled a number of times;
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@ -181,10 +190,10 @@ int nand_calculate_ecc(struct mtd_info *mtd, const unsigned char *buf,
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* Note: passing unaligned data might give a performance penalty.
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* It is assumed that the buffers are aligned.
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* tmppar is the cumulative sum of this iteration.
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* needed for calculating rp12, rp14 and par
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* needed for calculating rp12, rp14, rp16 and par
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* also used as a performance improvement for rp6, rp8 and rp10
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*/
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for (i = 0; i < 4; i++) {
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for (i = 0; i < eccsize_mult << 2; i++) {
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cur = *bp++;
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tmppar = cur;
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rp4 ^= cur;
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@ -247,12 +256,14 @@ int nand_calculate_ecc(struct mtd_info *mtd, const unsigned char *buf,
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rp12 ^= tmppar;
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if ((i & 0x2) == 0)
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rp14 ^= tmppar;
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if (eccsize_mult == 2 && (i & 0x4) == 0)
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rp16 ^= tmppar;
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}
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/*
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* handle the fact that we use longword operations
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* we'll bring rp4..rp14 back to single byte entities by shifting and
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* xoring first fold the upper and lower 16 bits,
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* we'll bring rp4..rp14..rp16 back to single byte entities by
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* shifting and xoring first fold the upper and lower 16 bits,
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* then the upper and lower 8 bits.
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*/
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rp4 ^= (rp4 >> 16);
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@ -273,6 +284,11 @@ int nand_calculate_ecc(struct mtd_info *mtd, const unsigned char *buf,
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rp14 ^= (rp14 >> 16);
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rp14 ^= (rp14 >> 8);
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rp14 &= 0xff;
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if (eccsize_mult == 2) {
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rp16 ^= (rp16 >> 16);
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rp16 ^= (rp16 >> 8);
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rp16 &= 0xff;
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}
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/*
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* we also need to calculate the row parity for rp0..rp3
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@ -315,7 +331,7 @@ int nand_calculate_ecc(struct mtd_info *mtd, const unsigned char *buf,
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par &= 0xff;
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/*
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* and calculate rp5..rp15
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* and calculate rp5..rp15..rp17
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* note that par = rp4 ^ rp5 and due to the commutative property
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* of the ^ operator we can say:
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* rp5 = (par ^ rp4);
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@ -329,6 +345,8 @@ int nand_calculate_ecc(struct mtd_info *mtd, const unsigned char *buf,
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rp11 = (par ^ rp10) & 0xff;
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rp13 = (par ^ rp12) & 0xff;
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rp15 = (par ^ rp14) & 0xff;
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if (eccsize_mult == 2)
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rp17 = (par ^ rp16) & 0xff;
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/*
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* Finally calculate the ecc bits.
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@ -375,32 +393,46 @@ int nand_calculate_ecc(struct mtd_info *mtd, const unsigned char *buf,
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(invparity[rp9] << 1) |
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(invparity[rp8]);
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#endif
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code[2] =
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(invparity[par & 0xf0] << 7) |
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(invparity[par & 0x0f] << 6) |
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(invparity[par & 0xcc] << 5) |
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(invparity[par & 0x33] << 4) |
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(invparity[par & 0xaa] << 3) |
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(invparity[par & 0x55] << 2) |
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3;
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if (eccsize_mult == 1)
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code[2] =
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(invparity[par & 0xf0] << 7) |
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(invparity[par & 0x0f] << 6) |
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(invparity[par & 0xcc] << 5) |
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(invparity[par & 0x33] << 4) |
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(invparity[par & 0xaa] << 3) |
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(invparity[par & 0x55] << 2) |
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3;
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else
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code[2] =
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(invparity[par & 0xf0] << 7) |
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(invparity[par & 0x0f] << 6) |
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(invparity[par & 0xcc] << 5) |
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(invparity[par & 0x33] << 4) |
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(invparity[par & 0xaa] << 3) |
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(invparity[par & 0x55] << 2) |
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(invparity[rp17] << 1) |
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(invparity[rp16] << 0);
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return 0;
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}
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EXPORT_SYMBOL(nand_calculate_ecc);
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/**
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* nand_correct_data - [NAND Interface] Detect and correct bit error(s)
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* @mtd: MTD block structure (unused)
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* @mtd: MTD block structure
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* @buf: raw data read from the chip
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* @read_ecc: ECC from the chip
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* @calc_ecc: the ECC calculated from raw data
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*
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* Detect and correct a 1 bit error for 256 byte block
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* Detect and correct a 1 bit error for 256/512 byte block
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*/
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int nand_correct_data(struct mtd_info *mtd, unsigned char *buf,
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unsigned char *read_ecc, unsigned char *calc_ecc)
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{
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unsigned char b0, b1, b2;
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unsigned char byte_addr, bit_addr;
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/* 256 or 512 bytes/ecc */
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const uint32_t eccsize_mult =
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(((struct nand_chip *)mtd->priv)->ecc.size) >> 8;
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/*
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* b0 to b2 indicate which bit is faulty (if any)
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@ -426,10 +458,12 @@ int nand_correct_data(struct mtd_info *mtd, unsigned char *buf,
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if ((((b0 ^ (b0 >> 1)) & 0x55) == 0x55) &&
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(((b1 ^ (b1 >> 1)) & 0x55) == 0x55) &&
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(((b2 ^ (b2 >> 1)) & 0x54) == 0x54)) { /* single bit error */
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((eccsize_mult == 1 && ((b2 ^ (b2 >> 1)) & 0x54) == 0x54) ||
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(eccsize_mult == 2 && ((b2 ^ (b2 >> 1)) & 0x55) == 0x55))) {
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/* single bit error */
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/*
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* rp15/13/11/9/7/5/3/1 indicate which byte is the faulty byte
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* cp 5/3/1 indicate the faulty bit.
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* rp17/rp15/13/11/9/7/5/3/1 indicate which byte is the faulty
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* byte, cp 5/3/1 indicate the faulty bit.
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* A lookup table (called addressbits) is used to filter
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* the bits from the byte they are in.
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* A marginal optimisation is possible by having three
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@ -443,7 +477,11 @@ int nand_correct_data(struct mtd_info *mtd, unsigned char *buf,
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* We could also do addressbits[b2] >> 1 but for the
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* performace it does not make any difference
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*/
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byte_addr = (addressbits[b1] << 4) + addressbits[b0];
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if (eccsize_mult == 1)
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byte_addr = (addressbits[b1] << 4) + addressbits[b0];
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else
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byte_addr = (addressbits[b2 & 0x3] << 8) +
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(addressbits[b1] << 4) + addressbits[b0];
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bit_addr = addressbits[b2 >> 2];
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/* flip the bit */
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buf[byte_addr] ^= (1 << bit_addr);
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