17c1d2be28
[Reported by Randy Dunlap] Signed-off-by: Alexey Korolev <akorolev@infradead.org> Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
464 lines
14 KiB
C
464 lines
14 KiB
C
/*
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* This file contains an ECC algorithm that detects and corrects 1 bit
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* errors in a 256 byte block of data.
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*
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* drivers/mtd/nand/nand_ecc.c
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*
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* Copyright © 2008 Koninklijke Philips Electronics NV.
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* Author: Frans Meulenbroeks
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*
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* Completely replaces the previous ECC implementation which was written by:
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* Steven J. Hill (sjhill@realitydiluted.com)
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* Thomas Gleixner (tglx@linutronix.de)
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*
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* Information on how this algorithm works and how it was developed
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* can be found in Documentation/mtd/nand_ecc.txt
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*
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* This file is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the
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* Free Software Foundation; either version 2 or (at your option) any
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* later version.
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*
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* This file is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this file; if not, write to the Free Software Foundation, Inc.,
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* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
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*
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*/
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/*
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* The STANDALONE macro is useful when running the code outside the kernel
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* e.g. when running the code in a testbed or a benchmark program.
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* When STANDALONE is used, the module related macros are commented out
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* as well as the linux include files.
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* Instead a private definition of mtd_info is given to satisfy the compiler
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* (the code does not use mtd_info, so the code does not care)
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*/
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#ifndef STANDALONE
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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/nand_ecc.h>
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#include <asm/byteorder.h>
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#else
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#include <stdint.h>
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struct mtd_info;
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#define EXPORT_SYMBOL(x) /* x */
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#define MODULE_LICENSE(x) /* x */
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#define MODULE_AUTHOR(x) /* x */
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#define MODULE_DESCRIPTION(x) /* x */
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#define printk printf
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#define KERN_ERR ""
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#endif
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/*
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* invparity is a 256 byte table that contains the odd parity
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* for each byte. So if the number of bits in a byte is even,
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* the array element is 1, and when the number of bits is odd
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* the array eleemnt is 0.
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*/
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static const char invparity[256] = {
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1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1,
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0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0,
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0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0,
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1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1,
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0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0,
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1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1,
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1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1,
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0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0,
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0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0,
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1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1,
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1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1,
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0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0,
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1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1,
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0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0,
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0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0,
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1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1
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};
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/*
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* bitsperbyte contains the number of bits per byte
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* this is only used for testing and repairing parity
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* (a precalculated value slightly improves performance)
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*/
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static const char bitsperbyte[256] = {
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0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4,
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1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
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1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
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2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
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1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
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2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
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2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
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3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
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1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
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2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
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2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
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3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
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2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
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3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
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3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
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4, 5, 5, 6, 5, 6, 6, 7, 5, 6, 6, 7, 6, 7, 7, 8,
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};
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/*
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* addressbits is a lookup table to filter out the bits from the xor-ed
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* ecc data that identify the faulty location.
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* this is only used for repairing parity
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* see the comments in nand_correct_data for more details
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*/
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static const char addressbits[256] = {
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0x00, 0x00, 0x01, 0x01, 0x00, 0x00, 0x01, 0x01,
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0x02, 0x02, 0x03, 0x03, 0x02, 0x02, 0x03, 0x03,
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0x00, 0x00, 0x01, 0x01, 0x00, 0x00, 0x01, 0x01,
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0x02, 0x02, 0x03, 0x03, 0x02, 0x02, 0x03, 0x03,
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0x04, 0x04, 0x05, 0x05, 0x04, 0x04, 0x05, 0x05,
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0x06, 0x06, 0x07, 0x07, 0x06, 0x06, 0x07, 0x07,
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0x04, 0x04, 0x05, 0x05, 0x04, 0x04, 0x05, 0x05,
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0x06, 0x06, 0x07, 0x07, 0x06, 0x06, 0x07, 0x07,
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0x00, 0x00, 0x01, 0x01, 0x00, 0x00, 0x01, 0x01,
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0x02, 0x02, 0x03, 0x03, 0x02, 0x02, 0x03, 0x03,
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0x00, 0x00, 0x01, 0x01, 0x00, 0x00, 0x01, 0x01,
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0x02, 0x02, 0x03, 0x03, 0x02, 0x02, 0x03, 0x03,
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0x04, 0x04, 0x05, 0x05, 0x04, 0x04, 0x05, 0x05,
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0x06, 0x06, 0x07, 0x07, 0x06, 0x06, 0x07, 0x07,
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0x04, 0x04, 0x05, 0x05, 0x04, 0x04, 0x05, 0x05,
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0x06, 0x06, 0x07, 0x07, 0x06, 0x06, 0x07, 0x07,
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0x08, 0x08, 0x09, 0x09, 0x08, 0x08, 0x09, 0x09,
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0x0a, 0x0a, 0x0b, 0x0b, 0x0a, 0x0a, 0x0b, 0x0b,
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0x08, 0x08, 0x09, 0x09, 0x08, 0x08, 0x09, 0x09,
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0x0a, 0x0a, 0x0b, 0x0b, 0x0a, 0x0a, 0x0b, 0x0b,
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0x0c, 0x0c, 0x0d, 0x0d, 0x0c, 0x0c, 0x0d, 0x0d,
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0x0e, 0x0e, 0x0f, 0x0f, 0x0e, 0x0e, 0x0f, 0x0f,
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0x0c, 0x0c, 0x0d, 0x0d, 0x0c, 0x0c, 0x0d, 0x0d,
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0x0e, 0x0e, 0x0f, 0x0f, 0x0e, 0x0e, 0x0f, 0x0f,
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0x08, 0x08, 0x09, 0x09, 0x08, 0x08, 0x09, 0x09,
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0x0a, 0x0a, 0x0b, 0x0b, 0x0a, 0x0a, 0x0b, 0x0b,
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0x08, 0x08, 0x09, 0x09, 0x08, 0x08, 0x09, 0x09,
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0x0a, 0x0a, 0x0b, 0x0b, 0x0a, 0x0a, 0x0b, 0x0b,
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0x0c, 0x0c, 0x0d, 0x0d, 0x0c, 0x0c, 0x0d, 0x0d,
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0x0e, 0x0e, 0x0f, 0x0f, 0x0e, 0x0e, 0x0f, 0x0f,
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0x0c, 0x0c, 0x0d, 0x0d, 0x0c, 0x0c, 0x0d, 0x0d,
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0x0e, 0x0e, 0x0f, 0x0f, 0x0e, 0x0e, 0x0f, 0x0f
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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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* @buf: input buffer with raw data
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* @code: output buffer with ECC
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*/
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int nand_calculate_ecc(struct mtd_info *mtd, const unsigned char *buf,
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unsigned char *code)
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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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uint32_t cur; /* current value in buffer */
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/* rp0..rp15 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 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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par = 0;
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rp4 = 0;
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rp6 = 0;
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rp8 = 0;
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rp10 = 0;
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rp12 = 0;
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rp14 = 0;
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/*
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* The loop is unrolled a number of times;
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* This avoids if statements to decide on which rp value to update
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* Also we process the data by longwords.
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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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* 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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cur = *bp++;
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tmppar = cur;
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rp4 ^= cur;
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cur = *bp++;
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tmppar ^= cur;
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rp6 ^= tmppar;
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cur = *bp++;
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tmppar ^= cur;
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rp4 ^= cur;
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cur = *bp++;
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tmppar ^= cur;
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rp8 ^= tmppar;
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cur = *bp++;
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tmppar ^= cur;
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rp4 ^= cur;
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rp6 ^= cur;
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cur = *bp++;
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tmppar ^= cur;
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rp6 ^= cur;
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cur = *bp++;
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tmppar ^= cur;
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rp4 ^= cur;
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cur = *bp++;
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tmppar ^= cur;
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rp10 ^= tmppar;
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cur = *bp++;
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tmppar ^= cur;
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rp4 ^= cur;
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rp6 ^= cur;
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rp8 ^= cur;
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cur = *bp++;
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tmppar ^= cur;
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rp6 ^= cur;
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rp8 ^= cur;
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cur = *bp++;
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tmppar ^= cur;
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rp4 ^= cur;
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rp8 ^= cur;
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cur = *bp++;
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tmppar ^= cur;
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rp8 ^= cur;
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cur = *bp++;
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tmppar ^= cur;
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rp4 ^= cur;
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rp6 ^= cur;
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cur = *bp++;
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tmppar ^= cur;
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rp6 ^= cur;
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cur = *bp++;
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tmppar ^= cur;
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rp4 ^= cur;
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cur = *bp++;
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tmppar ^= cur;
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par ^= tmppar;
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if ((i & 0x1) == 0)
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rp12 ^= tmppar;
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if ((i & 0x2) == 0)
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rp14 ^= 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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* then the upper and lower 8 bits.
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*/
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rp4 ^= (rp4 >> 16);
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rp4 ^= (rp4 >> 8);
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rp4 &= 0xff;
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rp6 ^= (rp6 >> 16);
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rp6 ^= (rp6 >> 8);
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rp6 &= 0xff;
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rp8 ^= (rp8 >> 16);
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rp8 ^= (rp8 >> 8);
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rp8 &= 0xff;
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rp10 ^= (rp10 >> 16);
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rp10 ^= (rp10 >> 8);
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rp10 &= 0xff;
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rp12 ^= (rp12 >> 16);
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rp12 ^= (rp12 >> 8);
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rp12 &= 0xff;
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rp14 ^= (rp14 >> 16);
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rp14 ^= (rp14 >> 8);
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rp14 &= 0xff;
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/*
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* we also need to calculate the row parity for rp0..rp3
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* This is present in par, because par is now
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* rp3 rp3 rp2 rp2 in little endian and
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* rp2 rp2 rp3 rp3 in big endian
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* as well as
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* rp1 rp0 rp1 rp0 in little endian and
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* rp0 rp1 rp0 rp1 in big endian
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* First calculate rp2 and rp3
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*/
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#ifdef __BIG_ENDIAN
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rp2 = (par >> 16);
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rp2 ^= (rp2 >> 8);
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rp2 &= 0xff;
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rp3 = par & 0xffff;
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rp3 ^= (rp3 >> 8);
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rp3 &= 0xff;
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#else
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rp3 = (par >> 16);
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rp3 ^= (rp3 >> 8);
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rp3 &= 0xff;
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rp2 = par & 0xffff;
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rp2 ^= (rp2 >> 8);
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rp2 &= 0xff;
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#endif
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/* reduce par to 16 bits then calculate rp1 and rp0 */
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par ^= (par >> 16);
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#ifdef __BIG_ENDIAN
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rp0 = (par >> 8) & 0xff;
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rp1 = (par & 0xff);
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#else
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rp1 = (par >> 8) & 0xff;
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rp0 = (par & 0xff);
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#endif
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/* finally reduce par to 8 bits */
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par ^= (par >> 8);
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par &= 0xff;
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/*
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* and calculate rp5..rp15
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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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* The & 0xff seems superfluous, but benchmarking learned that
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* leaving it out gives slightly worse results. No idea why, probably
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* it has to do with the way the pipeline in pentium is organized.
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*/
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rp5 = (par ^ rp4) & 0xff;
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rp7 = (par ^ rp6) & 0xff;
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rp9 = (par ^ rp8) & 0xff;
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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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/*
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* Finally calculate the ecc bits.
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* Again here it might seem that there are performance optimisations
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* possible, but benchmarks showed that on the system this is developed
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* the code below is the fastest
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*/
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#ifdef CONFIG_MTD_NAND_ECC_SMC
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code[0] =
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(invparity[rp7] << 7) |
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(invparity[rp6] << 6) |
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(invparity[rp5] << 5) |
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(invparity[rp4] << 4) |
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(invparity[rp3] << 3) |
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(invparity[rp2] << 2) |
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(invparity[rp1] << 1) |
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(invparity[rp0]);
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code[1] =
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(invparity[rp15] << 7) |
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(invparity[rp14] << 6) |
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(invparity[rp13] << 5) |
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(invparity[rp12] << 4) |
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(invparity[rp11] << 3) |
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(invparity[rp10] << 2) |
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(invparity[rp9] << 1) |
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(invparity[rp8]);
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#else
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code[1] =
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(invparity[rp7] << 7) |
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(invparity[rp6] << 6) |
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(invparity[rp5] << 5) |
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(invparity[rp4] << 4) |
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(invparity[rp3] << 3) |
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(invparity[rp2] << 2) |
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(invparity[rp1] << 1) |
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(invparity[rp0]);
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code[0] =
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(invparity[rp15] << 7) |
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(invparity[rp14] << 6) |
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(invparity[rp13] << 5) |
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(invparity[rp12] << 4) |
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(invparity[rp11] << 3) |
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(invparity[rp10] << 2) |
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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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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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* @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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*/
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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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|
|
|
/*
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* b0 to b2 indicate which bit is faulty (if any)
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|
* we might need the xor result more than once,
|
|
* so keep them in a local var
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|
*/
|
|
#ifdef CONFIG_MTD_NAND_ECC_SMC
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|
b0 = read_ecc[0] ^ calc_ecc[0];
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|
b1 = read_ecc[1] ^ calc_ecc[1];
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|
#else
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b0 = read_ecc[1] ^ calc_ecc[1];
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b1 = read_ecc[0] ^ calc_ecc[0];
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|
#endif
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b2 = read_ecc[2] ^ calc_ecc[2];
|
|
|
|
/* check if there are any bitfaults */
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|
|
|
/* repeated if statements are slightly more efficient than switch ... */
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|
/* ordered in order of likelihood */
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|
|
|
if ((b0 | b1 | b2) == 0)
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return 0; /* no error */
|
|
|
|
if ((((b0 ^ (b0 >> 1)) & 0x55) == 0x55) &&
|
|
(((b1 ^ (b1 >> 1)) & 0x55) == 0x55) &&
|
|
(((b2 ^ (b2 >> 1)) & 0x54) == 0x54)) { /* 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.
|
|
* 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
|
|
* different lookup tables.
|
|
* One as we have now (for b0), one for b2
|
|
* (that would avoid the >> 1), and one for b1 (with all values
|
|
* << 4). However it was felt that introducing two more tables
|
|
* hardly justify the gain.
|
|
*
|
|
* The b2 shift is there to get rid of the lowest two bits.
|
|
* We could also do addressbits[b2] >> 1 but for the
|
|
* performace it does not make any difference
|
|
*/
|
|
byte_addr = (addressbits[b1] << 4) + addressbits[b0];
|
|
bit_addr = addressbits[b2 >> 2];
|
|
/* flip the bit */
|
|
buf[byte_addr] ^= (1 << bit_addr);
|
|
return 1;
|
|
|
|
}
|
|
/* count nr of bits; use table lookup, faster than calculating it */
|
|
if ((bitsperbyte[b0] + bitsperbyte[b1] + bitsperbyte[b2]) == 1)
|
|
return 1; /* error in ecc data; no action needed */
|
|
|
|
printk(KERN_ERR "uncorrectable error : ");
|
|
return -1;
|
|
}
|
|
EXPORT_SYMBOL(nand_correct_data);
|
|
|
|
MODULE_LICENSE("GPL");
|
|
MODULE_AUTHOR("Frans Meulenbroeks <fransmeulenbroeks@gmail.com>");
|
|
MODULE_DESCRIPTION("Generic NAND ECC support");
|