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