152 lines
4.5 KiB
C
152 lines
4.5 KiB
C
|
/*
|
||
|
|
* Synopsis : Error Correction Codes (ECC) Algorithms.
|
||
|
|
*
|
||
|
|
* Copyright (c) 2008 STMicroelectronics Limited. All right reserved.
|
||
|
|
*
|
||
|
|
* May be copied or modified under the terms of the GNU General Public
|
||
|
|
* License Version 2.0 only. See linux/COPYING for more information.
|
||
|
|
*
|
||
|
|
* An ECC is a 3-byte code which can be used to detect and correct 1-bit
|
||
|
|
* errors (perhaps introduced by NAND flash defects) in a 128, 256, or
|
||
|
|
* 512-byte block of data.
|
||
|
|
*
|
||
|
|
* Features:
|
||
|
|
* - Correction of any 1-bit error in the data.
|
||
|
|
* - Detection of any 1-bit error in the ECC and whether the data is OK.
|
||
|
|
* - Detection of any 2-bit error in the data.
|
||
|
|
*
|
||
|
|
* Limitations:
|
||
|
|
* - CANNOT correct 2-bit errors.
|
||
|
|
* - Results for 3-bit errors (or worse) are UNDEFINED.
|
||
|
|
*
|
||
|
|
* This algorithm is only intended for use with data corrupted by a NAND
|
||
|
|
* flash - in which anything more than a 1-bit error is highly unlikely.
|
||
|
|
*
|
||
|
|
* DO NOT attempt to use it where the data may be more seriously corrupted.
|
||
|
|
* The algorithm WILL NOT always correct serious defects and may even report
|
||
|
|
* that the data is good.
|
||
|
|
*
|
||
|
|
* Usage
|
||
|
|
* =====
|
||
|
|
*
|
||
|
|
* Writing flash:
|
||
|
|
*
|
||
|
|
* 1) Prepare the data.
|
||
|
|
* 2) Generate an ECC for each 128, 256, or 512 bytes.
|
||
|
|
* stm_ecc_gen (data, ecc, ECC_256)
|
||
|
|
* 3) Write both to flash.
|
||
|
|
*
|
||
|
|
* Reading flash:
|
||
|
|
*
|
||
|
|
* 1) Read both data and ECC from flash.
|
||
|
|
* 2) Generate a fresh ECC for the read data.
|
||
|
|
* ecc_gen (read_data, new_ecc, ECC_256)
|
||
|
|
* 3) Compare the two ECCs and correct the data, if necessary.
|
||
|
|
* ecc_correct (read_data, read_ecc, new_ecc, ECC_256)
|
||
|
|
* 4) Check the return code:
|
||
|
|
* E_UN_CHK
|
||
|
|
* Data cannot be used - too badly corrupted.
|
||
|
|
* E_NO_CHK
|
||
|
|
* All is well.
|
||
|
|
* E_D1_CHK
|
||
|
|
* Data has been corrected, but the flash block contains an error.
|
||
|
|
* E_C1_CHK
|
||
|
|
* Data is OK, but the flash block contains an error in the ECC.
|
||
|
|
*
|
||
|
|
* If a read error occurs then you may want to consider moving the data to
|
||
|
|
* another flash block. If the read error is in the ECC then don't forget
|
||
|
|
* to generate a correct ECC before rewriting.
|
||
|
|
*
|
||
|
|
* ECC Format
|
||
|
|
* ==========
|
||
|
|
*
|
||
|
|
* Basic Format:
|
||
|
|
*
|
||
|
|
* byte 0 byte 1 byte2
|
||
|
|
*
|
||
|
|
* bit 0 LP0 LP8 LP16
|
||
|
|
* bit 1 LP1 LP9 LP17
|
||
|
|
* bit 2 LP2 LP10 ` CP0
|
||
|
|
* bit 3 LP3 LP11 CP1
|
||
|
|
* bit 4 LP4 LP12 CP2
|
||
|
|
* bit 5 LP5 LP13 CP3
|
||
|
|
* bit 6 LP6 LP14 CP4
|
||
|
|
* bit 7 LP7 LP15 CP5
|
||
|
|
*
|
||
|
|
* CP = Column parity
|
||
|
|
* LP = Line parity
|
||
|
|
*
|
||
|
|
* ECC_128:
|
||
|
|
*
|
||
|
|
* LP14-17 are not used. The unused bits are set to zero.
|
||
|
|
*
|
||
|
|
* This format is designed to match the format used by the error
|
||
|
|
* correcting EMI NAND Controller. It may NOT be compatible with other
|
||
|
|
* 128 byte ECCs.
|
||
|
|
*
|
||
|
|
* ECC_256:
|
||
|
|
*
|
||
|
|
* LP16-17 are not used. The unused bits are set to zero.
|
||
|
|
*
|
||
|
|
* ECC_512:
|
||
|
|
*
|
||
|
|
* All bits are used.
|
||
|
|
*
|
||
|
|
* This format is NOT compatible with the 512 byte ECC used by OSPlus.
|
||
|
|
* (At the time of writing, this can be resolved merely by inverting each
|
||
|
|
* bit in the ECC, but this may not be the case in future.)
|
||
|
|
*
|
||
|
|
* Changelog:
|
||
|
|
* 2009-02-25 Angus Clark <angus.clark@st.com>
|
||
|
|
* - Renamed, formatted, and edited for linux compatibility
|
||
|
|
*
|
||
|
|
*/
|
||
|
|
|
||
|
|
#ifndef STM_NAND_ECC_H
|
||
|
|
#define STM_NAND_ECC_H
|
||
|
|
|
||
|
|
#include <linux/types.h>
|
||
|
|
|
||
|
|
/* The ECC algorithms support three different data sizes. */
|
||
|
|
enum ecc_size
|
||
|
|
{
|
||
|
|
ECC_128 = 128,
|
||
|
|
ECC_256 = 256,
|
||
|
|
ECC_512 = 512
|
||
|
|
};
|
||
|
|
|
||
|
|
/* Return values from check function */
|
||
|
|
enum ecc_check
|
||
|
|
{
|
||
|
|
E_UN_CHK = -1, /* uncorrectable error. */
|
||
|
|
E_NO_CHK = 0, /* No Errors. */
|
||
|
|
E_D1_CHK = 1, /* 1-bit data error. */
|
||
|
|
E_C1_CHK = 2 /* 1-bit code error. */
|
||
|
|
};
|
||
|
|
|
||
|
|
/* Generate 3 byte ECC code for ecc_size block p_data.
|
||
|
|
"p_data" is a pointer to the date and must be 4-byte aligned.
|
||
|
|
"size" gives length of "p_data" - one of enum ecc_size.
|
||
|
|
*/
|
||
|
|
void stm_ecc_gen(const uint8_t *p_data, uint8_t *ecc,
|
||
|
|
enum ecc_size size);
|
||
|
|
|
||
|
|
/* Detect and correct a 1 bit error in a 128, 256 or 512 byte block.
|
||
|
|
"p_data" is a pointer to the data.
|
||
|
|
"old_ecc" is the proper ECC for the data.
|
||
|
|
"new_ecc" is the ECC generated from the (possibly) corrupted data.
|
||
|
|
The size of the block is given in "size".
|
||
|
|
|
||
|
|
Returns whether the data needed correcting, or was not correctable.
|
||
|
|
If the result code is E_D1_CHK, then the data will have been modified.
|
||
|
|
*/
|
||
|
|
enum ecc_check stm_ecc_correct(uint8_t *p_data,
|
||
|
|
uint8_t *old_ecc,
|
||
|
|
uint8_t *new_ecc,
|
||
|
|
enum ecc_size size);
|
||
|
|
|
||
|
|
unsigned char stm_afm_lp1617(const unsigned char *buf);
|
||
|
|
|
||
|
|
#endif /* ifndef STM_NAND_ECC_H */
|
||
|
|
|