diff options
Diffstat (limited to 'drivers/mtd/nand/gpmi/gpmi-hamming-13-8.c')
| -rw-r--r-- | drivers/mtd/nand/gpmi/gpmi-hamming-13-8.c | 131 |
1 files changed, 131 insertions, 0 deletions
diff --git a/drivers/mtd/nand/gpmi/gpmi-hamming-13-8.c b/drivers/mtd/nand/gpmi/gpmi-hamming-13-8.c new file mode 100644 index 000000000000..c48d70b38bc0 --- /dev/null +++ b/drivers/mtd/nand/gpmi/gpmi-hamming-13-8.c @@ -0,0 +1,131 @@ +/* + * Freescale STMP37XX/STMP378X GPMI (General-Purpose-Media-Interface) + * + * NCB software ECC Hamming code + * + * Author: dmitry pervushin <dimka@embeddedalley.com> + * + * Copyright 2008-2009 Freescale Semiconductor, Inc. All Rights Reserved. + * Copyright 2008 Embedded Alley Solutions, Inc All Rights Reserved. + */ + +/* + * The code contained herein is licensed under the GNU General Public + * License. You may obtain a copy of the GNU General Public License + * Version 2 or later at the following locations: + * + * http://www.opensource.org/licenses/gpl-license.html + * http://www.gnu.org/copyleft/gpl.html + */ +#include <linux/platform_device.h> +#include <linux/mtd/mtd.h> +#include <linux/mtd/nand.h> +#include <linux/slab.h> +#include <linux/ctype.h> +#include <mach/dma.h> +#include "gpmi.h" + +#define BIT_VAL(v, n) (((v) >> (n)) & 0x1) +#define B(n) (BIT_VAL(d, n)) + +static u8 calculate_parity(u8 d) +{ + u8 p = 0; + + if (d == 0 || d == 0xFF) + return 0; /* optimization :) */ + + p |= (B(6) ^ B(5) ^ B(3) ^ B(2)) << 0; + p |= (B(7) ^ B(5) ^ B(4) ^ B(2) ^ B(1)) << 1; + p |= (B(7) ^ B(6) ^ B(5) ^ B(1) ^ B(0)) << 2; + p |= (B(7) ^ B(4) ^ B(3) ^ B(0)) << 3; + p |= (B(6) ^ B(4) ^ B(3) ^ B(2) ^ B(1) ^ B(0)) << 4; + return p; +} + +static inline int even_number_of_1s(u8 byte) +{ + int even = 1; + + while (byte > 0) { + even ^= (byte & 0x1); + byte >>= 1; + } + return even; +} + +static int lookup_single_error(u8 syndrome) +{ + int i; + u8 syndrome_table[] = { + 0x1C, 0x16, 0x13, 0x19, + 0x1A, 0x07, 0x15, 0x0E, + 0x01, 0x02, 0x04, 0x08, + 0x10, + }; + + for (i = 0; i < ARRAY_SIZE(syndrome_table); i++) + if (syndrome_table[i] == syndrome) + return i; + return -ENOENT; +} + +int gpmi_verify_hamming_13_8(void *data, u8 *parity, size_t size) +{ + int i; + u8 *pdata = data; + int bit_to_flip; + u8 np, syndrome; + int errors = 0; + + for (i = 0; i < size; i ++, pdata++) { + np = calculate_parity(*pdata); + syndrome = np ^ parity[i]; + if (syndrome == 0) /* cool */ { + continue; + } + + if (even_number_of_1s(syndrome)) + return -i; /* can't recover */ + + bit_to_flip = lookup_single_error(syndrome); + if (bit_to_flip < 0) + return -i; /* can't fix the error */ + + if (bit_to_flip < 8) { + *pdata ^= (1 << bit_to_flip); + errors++; + } + } + return errors; +} + +void gpmi_encode_hamming_13_8(void *source_block, size_t src_size, + void *source_ecc, size_t ecc_size) +{ + int i; + u8 *src = source_block; + u8 *ecc = source_ecc; + + for (i = 0; i < src_size && i < ecc_size; i++) + ecc[i] = calculate_parity(src[i]); +} + +void gpmi_encode_hamming_ncb_13_8(void *source_block, size_t source_size, + void *target_block, size_t target_size) +{ + if (target_size < 12 + 2 * NAND_HC_ECC_SIZEOF_DATA_BLOCK_IN_BYTES) + return; + memset(target_block, 0xFF, target_size); + memcpy((u8 *)target_block + 12, source_block, source_size); + gpmi_encode_hamming_13_8(source_block, + NAND_HC_ECC_SIZEOF_DATA_BLOCK_IN_BYTES, + (u8 *)target_block + 12 + NAND_HC_ECC_SIZEOF_DATA_BLOCK_IN_BYTES, + NAND_HC_ECC_SIZEOF_DATA_BLOCK_IN_BYTES); +} + +unsigned gpmi_hamming_ecc_size_13_8(int block_size) +{ + return block_size; +} + |