Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752837Ab0K3V56 (ORCPT ); Tue, 30 Nov 2010 16:57:58 -0500 Received: from mail-px0-f174.google.com ([209.85.212.174]:33923 "EHLO mail-px0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752677Ab0K3V54 (ORCPT ); Tue, 30 Nov 2010 16:57:56 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=from:to:cc:subject:date:message-id:x-mailer:in-reply-to:references; b=f9zX/ReLVbOrG9lEMbNNKDNPMyFYXiii8ob5FjHSsgwDuyJfQ0ujYx8WAPKZaXgk+x Dq/gCv5XrlFbyxdilFo2Yr03kXTUjZav+C5ju6IgUfRXGOrfTsMwrTq4R7+x3ZnEkFux vlPqKpvw11Wc8fVomhRcgqxcsFxOHLgSlb180= From: Charles Manning To: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Charles Manning Subject: [PATCH 2/8] Add yaffs2 file system: checkpoint and ecc code Date: Wed, 1 Dec 2010 10:57:28 +1300 Message-Id: <1291154254-22533-3-git-send-email-cdhmanning@gmail.com> X-Mailer: git-send-email 1.7.1 In-Reply-To: <1291154254-22533-1-git-send-email-cdhmanning@gmail.com> References: <1291154254-22533-1-git-send-email-cdhmanning@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 22914 Lines: 839 Signed-off-by: Charles Manning --- fs/yaffs2/yaffs_checkptrw.c | 420 +++++++++++++++++++++++++++++++++++++++++++ fs/yaffs2/yaffs_checkptrw.h | 33 ++++ fs/yaffs2/yaffs_ecc.c | 298 ++++++++++++++++++++++++++++++ fs/yaffs2/yaffs_ecc.h | 44 +++++ 4 files changed, 795 insertions(+), 0 deletions(-) create mode 100644 fs/yaffs2/yaffs_checkptrw.c create mode 100644 fs/yaffs2/yaffs_checkptrw.h create mode 100644 fs/yaffs2/yaffs_ecc.c create mode 100644 fs/yaffs2/yaffs_ecc.h diff --git a/fs/yaffs2/yaffs_checkptrw.c b/fs/yaffs2/yaffs_checkptrw.c new file mode 100644 index 0000000..02b8ce6 --- /dev/null +++ b/fs/yaffs2/yaffs_checkptrw.c @@ -0,0 +1,420 @@ +/* + * YAFFS: Yet Another Flash File System. A NAND-flash specific file system. + * + * Copyright (C) 2002-2010 Aleph One Ltd. + * for Toby Churchill Ltd and Brightstar Engineering + * + * Created by Charles Manning + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + */ + +#include "yaffs_checkptrw.h" +#include "yaffs_getblockinfo.h" + +static int yaffs2_checkpt_space_ok(struct yaffs_dev *dev) +{ + int blocks_avail = dev->n_erased_blocks - dev->param.n_reserved_blocks; + + T(YAFFS_TRACE_CHECKPOINT, + (TSTR("checkpt blocks available = %d" TENDSTR), blocks_avail)); + + return (blocks_avail <= 0) ? 0 : 1; +} + +static int yaffs_checkpt_erase(struct yaffs_dev *dev) +{ + int i; + + if (!dev->param.erase_fn) + return 0; + T(YAFFS_TRACE_CHECKPOINT, (TSTR("checking blocks %d to %d" TENDSTR), + dev->internal_start_block, + dev->internal_end_block)); + + for (i = dev->internal_start_block; i <= dev->internal_end_block; i++) { + struct yaffs_block_info *bi = yaffs_get_block_info(dev, i); + if (bi->block_state == YAFFS_BLOCK_STATE_CHECKPOINT) { + T(YAFFS_TRACE_CHECKPOINT, + (TSTR("erasing checkpt block %d" TENDSTR), i)); + + dev->n_erasures++; + + if (dev->param. + erase_fn(dev, + i - dev->block_offset /* realign */ )) { + bi->block_state = YAFFS_BLOCK_STATE_EMPTY; + dev->n_erased_blocks++; + dev->n_free_chunks += + dev->param.chunks_per_block; + } else { + dev->param.bad_block_fn(dev, i); + bi->block_state = YAFFS_BLOCK_STATE_DEAD; + } + } + } + + dev->blocks_in_checkpt = 0; + + return 1; +} + +static void yaffs2_checkpt_find_erased_block(struct yaffs_dev *dev) +{ + int i; + int blocks_avail = dev->n_erased_blocks - dev->param.n_reserved_blocks; + T(YAFFS_TRACE_CHECKPOINT, + (TSTR + ("allocating checkpt block: erased %d reserved %d avail %d next %d " + TENDSTR), dev->n_erased_blocks, dev->param.n_reserved_blocks, + blocks_avail, dev->checkpt_next_block)); + + if (dev->checkpt_next_block >= 0 && + dev->checkpt_next_block <= dev->internal_end_block && + blocks_avail > 0) { + + for (i = dev->checkpt_next_block; i <= dev->internal_end_block; + i++) { + struct yaffs_block_info *bi = + yaffs_get_block_info(dev, i); + if (bi->block_state == YAFFS_BLOCK_STATE_EMPTY) { + dev->checkpt_next_block = i + 1; + dev->checkpt_cur_block = i; + T(YAFFS_TRACE_CHECKPOINT, + (TSTR("allocating checkpt block %d" TENDSTR), + i)); + return; + } + } + } + T(YAFFS_TRACE_CHECKPOINT, (TSTR("out of checkpt blocks" TENDSTR))); + + dev->checkpt_next_block = -1; + dev->checkpt_cur_block = -1; +} + +static void yaffs2_checkpt_find_block(struct yaffs_dev *dev) +{ + int i; + struct yaffs_ext_tags tags; + + T(YAFFS_TRACE_CHECKPOINT, + (TSTR("find next checkpt block: start: blocks %d next %d" TENDSTR), + dev->blocks_in_checkpt, dev->checkpt_next_block)); + + if (dev->blocks_in_checkpt < dev->checkpt_max_blocks) + for (i = dev->checkpt_next_block; i <= dev->internal_end_block; + i++) { + int chunk = i * dev->param.chunks_per_block; + int realigned_chunk = chunk - dev->chunk_offset; + + dev->param.read_chunk_tags_fn(dev, realigned_chunk, + NULL, &tags); + T(YAFFS_TRACE_CHECKPOINT, + (TSTR + ("find next checkpt block: search: block %d oid %d seq %d eccr %d" + TENDSTR), i, tags.obj_id, tags.seq_number, + tags.ecc_result)); + + if (tags.seq_number == YAFFS_SEQUENCE_CHECKPOINT_DATA) { + /* Right kind of block */ + dev->checkpt_next_block = tags.obj_id; + dev->checkpt_cur_block = i; + dev->checkpt_block_list[dev-> + blocks_in_checkpt] = i; + dev->blocks_in_checkpt++; + T(YAFFS_TRACE_CHECKPOINT, + (TSTR("found checkpt block %d" TENDSTR), i)); + return; + } + } + + T(YAFFS_TRACE_CHECKPOINT, + (TSTR("found no more checkpt blocks" TENDSTR))); + + dev->checkpt_next_block = -1; + dev->checkpt_cur_block = -1; +} + +int yaffs2_checkpt_open(struct yaffs_dev *dev, int writing) +{ + + dev->checkpt_open_write = writing; + + /* Got the functions we need? */ + if (!dev->param.write_chunk_tags_fn || + !dev->param.read_chunk_tags_fn || + !dev->param.erase_fn || !dev->param.bad_block_fn) + return 0; + + if (writing && !yaffs2_checkpt_space_ok(dev)) + return 0; + + if (!dev->checkpt_buffer) + dev->checkpt_buffer = + YMALLOC_DMA(dev->param.total_bytes_per_chunk); + if (!dev->checkpt_buffer) + return 0; + + dev->checkpt_page_seq = 0; + dev->checkpt_byte_count = 0; + dev->checkpt_sum = 0; + dev->checkpt_xor = 0; + dev->checkpt_cur_block = -1; + dev->checkpt_cur_chunk = -1; + dev->checkpt_next_block = dev->internal_start_block; + + /* Erase all the blocks in the checkpoint area */ + if (writing) { + memset(dev->checkpt_buffer, 0, dev->data_bytes_per_chunk); + dev->checkpt_byte_offs = 0; + return yaffs_checkpt_erase(dev); + } else { + int i; + /* Set to a value that will kick off a read */ + dev->checkpt_byte_offs = dev->data_bytes_per_chunk; + /* A checkpoint block list of 1 checkpoint block per 16 block is (hopefully) + * going to be way more than we need */ + dev->blocks_in_checkpt = 0; + dev->checkpt_max_blocks = + (dev->internal_end_block - dev->internal_start_block) / 16 + + 2; + dev->checkpt_block_list = + YMALLOC(sizeof(int) * dev->checkpt_max_blocks); + if (!dev->checkpt_block_list) + return 0; + + for (i = 0; i < dev->checkpt_max_blocks; i++) + dev->checkpt_block_list[i] = -1; + } + + return 1; +} + +int yaffs2_get_checkpt_sum(struct yaffs_dev *dev, u32 * sum) +{ + u32 composite_sum; + composite_sum = (dev->checkpt_sum << 8) | (dev->checkpt_xor & 0xFF); + *sum = composite_sum; + return 1; +} + +static int yaffs2_checkpt_flush_buffer(struct yaffs_dev *dev) +{ + int chunk; + int realigned_chunk; + + struct yaffs_ext_tags tags; + + if (dev->checkpt_cur_block < 0) { + yaffs2_checkpt_find_erased_block(dev); + dev->checkpt_cur_chunk = 0; + } + + if (dev->checkpt_cur_block < 0) + return 0; + + tags.is_deleted = 0; + tags.obj_id = dev->checkpt_next_block; /* Hint to next place to look */ + tags.chunk_id = dev->checkpt_page_seq + 1; + tags.seq_number = YAFFS_SEQUENCE_CHECKPOINT_DATA; + tags.n_bytes = dev->data_bytes_per_chunk; + if (dev->checkpt_cur_chunk == 0) { + /* First chunk we write for the block? Set block state to + checkpoint */ + struct yaffs_block_info *bi = + yaffs_get_block_info(dev, dev->checkpt_cur_block); + bi->block_state = YAFFS_BLOCK_STATE_CHECKPOINT; + dev->blocks_in_checkpt++; + } + + chunk = + dev->checkpt_cur_block * dev->param.chunks_per_block + + dev->checkpt_cur_chunk; + + T(YAFFS_TRACE_CHECKPOINT, + (TSTR + ("checkpoint wite buffer nand %d(%d:%d) objid %d chId %d" TENDSTR), + chunk, dev->checkpt_cur_block, dev->checkpt_cur_chunk, tags.obj_id, + tags.chunk_id)); + + realigned_chunk = chunk - dev->chunk_offset; + + dev->n_page_writes++; + + dev->param.write_chunk_tags_fn(dev, realigned_chunk, + dev->checkpt_buffer, &tags); + dev->checkpt_byte_offs = 0; + dev->checkpt_page_seq++; + dev->checkpt_cur_chunk++; + if (dev->checkpt_cur_chunk >= dev->param.chunks_per_block) { + dev->checkpt_cur_chunk = 0; + dev->checkpt_cur_block = -1; + } + memset(dev->checkpt_buffer, 0, dev->data_bytes_per_chunk); + + return 1; +} + +int yaffs2_checkpt_wr(struct yaffs_dev *dev, const void *data, int n_bytes) +{ + int i = 0; + int ok = 1; + + u8 *data_bytes = (u8 *) data; + + if (!dev->checkpt_buffer) + return 0; + + if (!dev->checkpt_open_write) + return -1; + + while (i < n_bytes && ok) { + dev->checkpt_buffer[dev->checkpt_byte_offs] = *data_bytes; + dev->checkpt_sum += *data_bytes; + dev->checkpt_xor ^= *data_bytes; + + dev->checkpt_byte_offs++; + i++; + data_bytes++; + dev->checkpt_byte_count++; + + if (dev->checkpt_byte_offs < 0 || + dev->checkpt_byte_offs >= dev->data_bytes_per_chunk) + ok = yaffs2_checkpt_flush_buffer(dev); + } + + return i; +} + +int yaffs2_checkpt_rd(struct yaffs_dev *dev, void *data, int n_bytes) +{ + int i = 0; + int ok = 1; + struct yaffs_ext_tags tags; + + int chunk; + int realigned_chunk; + + u8 *data_bytes = (u8 *) data; + + if (!dev->checkpt_buffer) + return 0; + + if (dev->checkpt_open_write) + return -1; + + while (i < n_bytes && ok) { + + if (dev->checkpt_byte_offs < 0 || + dev->checkpt_byte_offs >= dev->data_bytes_per_chunk) { + + if (dev->checkpt_cur_block < 0) { + yaffs2_checkpt_find_block(dev); + dev->checkpt_cur_chunk = 0; + } + + if (dev->checkpt_cur_block < 0) + ok = 0; + else { + chunk = dev->checkpt_cur_block * + dev->param.chunks_per_block + + dev->checkpt_cur_chunk; + + realigned_chunk = chunk - dev->chunk_offset; + + dev->n_page_reads++; + + /* read in the next chunk */ + dev->param.read_chunk_tags_fn(dev, + realigned_chunk, + dev-> + checkpt_buffer, + &tags); + + if (tags.chunk_id != (dev->checkpt_page_seq + 1) + || tags.ecc_result > YAFFS_ECC_RESULT_FIXED + || tags.seq_number != + YAFFS_SEQUENCE_CHECKPOINT_DATA) + ok = 0; + + dev->checkpt_byte_offs = 0; + dev->checkpt_page_seq++; + dev->checkpt_cur_chunk++; + + if (dev->checkpt_cur_chunk >= + dev->param.chunks_per_block) + dev->checkpt_cur_block = -1; + } + } + + if (ok) { + *data_bytes = + dev->checkpt_buffer[dev->checkpt_byte_offs]; + dev->checkpt_sum += *data_bytes; + dev->checkpt_xor ^= *data_bytes; + dev->checkpt_byte_offs++; + i++; + data_bytes++; + dev->checkpt_byte_count++; + } + } + + return i; +} + +int yaffs_checkpt_close(struct yaffs_dev *dev) +{ + + if (dev->checkpt_open_write) { + if (dev->checkpt_byte_offs != 0) + yaffs2_checkpt_flush_buffer(dev); + } else if (dev->checkpt_block_list) { + int i; + for (i = 0; + i < dev->blocks_in_checkpt + && dev->checkpt_block_list[i] >= 0; i++) { + int blk = dev->checkpt_block_list[i]; + struct yaffs_block_info *bi = NULL; + if (dev->internal_start_block <= blk + && blk <= dev->internal_end_block) + bi = yaffs_get_block_info(dev, blk); + if (bi && bi->block_state == YAFFS_BLOCK_STATE_EMPTY) + bi->block_state = YAFFS_BLOCK_STATE_CHECKPOINT; + else { + /* Todo this looks odd... */ + } + } + YFREE(dev->checkpt_block_list); + dev->checkpt_block_list = NULL; + } + + dev->n_free_chunks -= + dev->blocks_in_checkpt * dev->param.chunks_per_block; + dev->n_erased_blocks -= dev->blocks_in_checkpt; + + T(YAFFS_TRACE_CHECKPOINT, (TSTR("checkpoint byte count %d" TENDSTR), + dev->checkpt_byte_count)); + + if (dev->checkpt_buffer) { + /* free the buffer */ + YFREE(dev->checkpt_buffer); + dev->checkpt_buffer = NULL; + return 1; + } else { + return 0; + } +} + +int yaffs2_checkpt_invalidate_stream(struct yaffs_dev *dev) +{ + /* Erase the checkpoint data */ + + T(YAFFS_TRACE_CHECKPOINT, + (TSTR("checkpoint invalidate of %d blocks" TENDSTR), + dev->blocks_in_checkpt)); + + return yaffs_checkpt_erase(dev); +} diff --git a/fs/yaffs2/yaffs_checkptrw.h b/fs/yaffs2/yaffs_checkptrw.h new file mode 100644 index 0000000..361c606 --- /dev/null +++ b/fs/yaffs2/yaffs_checkptrw.h @@ -0,0 +1,33 @@ +/* + * YAFFS: Yet another Flash File System . A NAND-flash specific file system. + * + * Copyright (C) 2002-2010 Aleph One Ltd. + * for Toby Churchill Ltd and Brightstar Engineering + * + * Created by Charles Manning + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU Lesser General Public License version 2.1 as + * published by the Free Software Foundation. + * + * Note: Only YAFFS headers are LGPL, YAFFS C code is covered by GPL. + */ + +#ifndef __YAFFS_CHECKPTRW_H__ +#define __YAFFS_CHECKPTRW_H__ + +#include "yaffs_guts.h" + +int yaffs2_checkpt_open(struct yaffs_dev *dev, int writing); + +int yaffs2_checkpt_wr(struct yaffs_dev *dev, const void *data, int n_bytes); + +int yaffs2_checkpt_rd(struct yaffs_dev *dev, void *data, int n_bytes); + +int yaffs2_get_checkpt_sum(struct yaffs_dev *dev, u32 * sum); + +int yaffs_checkpt_close(struct yaffs_dev *dev); + +int yaffs2_checkpt_invalidate_stream(struct yaffs_dev *dev); + +#endif diff --git a/fs/yaffs2/yaffs_ecc.c b/fs/yaffs2/yaffs_ecc.c new file mode 100644 index 0000000..e95a806 --- /dev/null +++ b/fs/yaffs2/yaffs_ecc.c @@ -0,0 +1,298 @@ +/* + * YAFFS: Yet Another Flash File System. A NAND-flash specific file system. + * + * Copyright (C) 2002-2010 Aleph One Ltd. + * for Toby Churchill Ltd and Brightstar Engineering + * + * Created by Charles Manning + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + */ + +/* + * This code implements the ECC algorithm used in SmartMedia. + * + * The ECC comprises 22 bits of parity information and is stuffed into 3 bytes. + * The two unused bit are set to 1. + * The ECC can correct single bit errors in a 256-byte page of data. Thus, two such ECC + * blocks are used on a 512-byte NAND page. + * + */ + +/* Table generated by gen-ecc.c + * Using a table means we do not have to calculate p1..p4 and p1'..p4' + * for each byte of data. These are instead provided in a table in bits7..2. + * Bit 0 of each entry indicates whether the entry has an odd or even parity, and therefore + * this bytes influence on the line parity. + */ + +#include "yportenv.h" + +#include "yaffs_ecc.h" + +static const unsigned char column_parity_table[] = { + 0x00, 0x55, 0x59, 0x0c, 0x65, 0x30, 0x3c, 0x69, + 0x69, 0x3c, 0x30, 0x65, 0x0c, 0x59, 0x55, 0x00, + 0x95, 0xc0, 0xcc, 0x99, 0xf0, 0xa5, 0xa9, 0xfc, + 0xfc, 0xa9, 0xa5, 0xf0, 0x99, 0xcc, 0xc0, 0x95, + 0x99, 0xcc, 0xc0, 0x95, 0xfc, 0xa9, 0xa5, 0xf0, + 0xf0, 0xa5, 0xa9, 0xfc, 0x95, 0xc0, 0xcc, 0x99, + 0x0c, 0x59, 0x55, 0x00, 0x69, 0x3c, 0x30, 0x65, + 0x65, 0x30, 0x3c, 0x69, 0x00, 0x55, 0x59, 0x0c, + 0xa5, 0xf0, 0xfc, 0xa9, 0xc0, 0x95, 0x99, 0xcc, + 0xcc, 0x99, 0x95, 0xc0, 0xa9, 0xfc, 0xf0, 0xa5, + 0x30, 0x65, 0x69, 0x3c, 0x55, 0x00, 0x0c, 0x59, + 0x59, 0x0c, 0x00, 0x55, 0x3c, 0x69, 0x65, 0x30, + 0x3c, 0x69, 0x65, 0x30, 0x59, 0x0c, 0x00, 0x55, + 0x55, 0x00, 0x0c, 0x59, 0x30, 0x65, 0x69, 0x3c, + 0xa9, 0xfc, 0xf0, 0xa5, 0xcc, 0x99, 0x95, 0xc0, + 0xc0, 0x95, 0x99, 0xcc, 0xa5, 0xf0, 0xfc, 0xa9, + 0xa9, 0xfc, 0xf0, 0xa5, 0xcc, 0x99, 0x95, 0xc0, + 0xc0, 0x95, 0x99, 0xcc, 0xa5, 0xf0, 0xfc, 0xa9, + 0x3c, 0x69, 0x65, 0x30, 0x59, 0x0c, 0x00, 0x55, + 0x55, 0x00, 0x0c, 0x59, 0x30, 0x65, 0x69, 0x3c, + 0x30, 0x65, 0x69, 0x3c, 0x55, 0x00, 0x0c, 0x59, + 0x59, 0x0c, 0x00, 0x55, 0x3c, 0x69, 0x65, 0x30, + 0xa5, 0xf0, 0xfc, 0xa9, 0xc0, 0x95, 0x99, 0xcc, + 0xcc, 0x99, 0x95, 0xc0, 0xa9, 0xfc, 0xf0, 0xa5, + 0x0c, 0x59, 0x55, 0x00, 0x69, 0x3c, 0x30, 0x65, + 0x65, 0x30, 0x3c, 0x69, 0x00, 0x55, 0x59, 0x0c, + 0x99, 0xcc, 0xc0, 0x95, 0xfc, 0xa9, 0xa5, 0xf0, + 0xf0, 0xa5, 0xa9, 0xfc, 0x95, 0xc0, 0xcc, 0x99, + 0x95, 0xc0, 0xcc, 0x99, 0xf0, 0xa5, 0xa9, 0xfc, + 0xfc, 0xa9, 0xa5, 0xf0, 0x99, 0xcc, 0xc0, 0x95, + 0x00, 0x55, 0x59, 0x0c, 0x65, 0x30, 0x3c, 0x69, + 0x69, 0x3c, 0x30, 0x65, 0x0c, 0x59, 0x55, 0x00, +}; + + +/* Calculate the ECC for a 256-byte block of data */ +void yaffs_ecc_cacl(const unsigned char *data, unsigned char *ecc) +{ + unsigned int i; + + unsigned char col_parity = 0; + unsigned char line_parity = 0; + unsigned char line_parity_prime = 0; + unsigned char t; + unsigned char b; + + for (i = 0; i < 256; i++) { + b = column_parity_table[*data++]; + col_parity ^= b; + + if (b & 0x01) { /* odd number of bits in the byte */ + line_parity ^= i; + line_parity_prime ^= ~i; + } + } + + ecc[2] = (~col_parity) | 0x03; + + t = 0; + if (line_parity & 0x80) + t |= 0x80; + if (line_parity_prime & 0x80) + t |= 0x40; + if (line_parity & 0x40) + t |= 0x20; + if (line_parity_prime & 0x40) + t |= 0x10; + if (line_parity & 0x20) + t |= 0x08; + if (line_parity_prime & 0x20) + t |= 0x04; + if (line_parity & 0x10) + t |= 0x02; + if (line_parity_prime & 0x10) + t |= 0x01; + ecc[1] = ~t; + + t = 0; + if (line_parity & 0x08) + t |= 0x80; + if (line_parity_prime & 0x08) + t |= 0x40; + if (line_parity & 0x04) + t |= 0x20; + if (line_parity_prime & 0x04) + t |= 0x10; + if (line_parity & 0x02) + t |= 0x08; + if (line_parity_prime & 0x02) + t |= 0x04; + if (line_parity & 0x01) + t |= 0x02; + if (line_parity_prime & 0x01) + t |= 0x01; + ecc[0] = ~t; + +#ifdef CONFIG_YAFFS_ECC_WRONG_ORDER + /* Swap the bytes into the wrong order */ + t = ecc[0]; + ecc[0] = ecc[1]; + ecc[1] = t; +#endif +} + +/* Correct the ECC on a 256 byte block of data */ + +int yaffs_ecc_correct(unsigned char *data, unsigned char *read_ecc, + const unsigned char *test_ecc) +{ + unsigned char d0, d1, d2; /* deltas */ + + d0 = read_ecc[0] ^ test_ecc[0]; + d1 = read_ecc[1] ^ test_ecc[1]; + d2 = read_ecc[2] ^ test_ecc[2]; + + if ((d0 | d1 | d2) == 0) + return 0; /* no error */ + + if (((d0 ^ (d0 >> 1)) & 0x55) == 0x55 && + ((d1 ^ (d1 >> 1)) & 0x55) == 0x55 && + ((d2 ^ (d2 >> 1)) & 0x54) == 0x54) { + /* Single bit (recoverable) error in data */ + + unsigned byte; + unsigned bit; + +#ifdef CONFIG_YAFFS_ECC_WRONG_ORDER + /* swap the bytes to correct for the wrong order */ + unsigned char t; + + t = d0; + d0 = d1; + d1 = t; +#endif + + bit = byte = 0; + + if (d1 & 0x80) + byte |= 0x80; + if (d1 & 0x20) + byte |= 0x40; + if (d1 & 0x08) + byte |= 0x20; + if (d1 & 0x02) + byte |= 0x10; + if (d0 & 0x80) + byte |= 0x08; + if (d0 & 0x20) + byte |= 0x04; + if (d0 & 0x08) + byte |= 0x02; + if (d0 & 0x02) + byte |= 0x01; + + if (d2 & 0x80) + bit |= 0x04; + if (d2 & 0x20) + bit |= 0x02; + if (d2 & 0x08) + bit |= 0x01; + + data[byte] ^= (1 << bit); + + return 1; /* Corrected the error */ + } + + if ((hweight8(d0) + hweight8(d1) + hweight8(d2)) == 1) { + /* Reccoverable error in ecc */ + + read_ecc[0] = test_ecc[0]; + read_ecc[1] = test_ecc[1]; + read_ecc[2] = test_ecc[2]; + + return 1; /* Corrected the error */ + } + + /* Unrecoverable error */ + + return -1; + +} + +/* + * ECCxxxOther does ECC calcs on arbitrary n bytes of data + */ +void yaffs_ecc_calc_other(const unsigned char *data, unsigned n_bytes, + struct yaffs_ecc_other *ecc_other) +{ + unsigned int i; + + unsigned char col_parity = 0; + unsigned line_parity = 0; + unsigned line_parity_prime = 0; + unsigned char b; + + for (i = 0; i < n_bytes; i++) { + b = column_parity_table[*data++]; + col_parity ^= b; + + if (b & 0x01) { + /* odd number of bits in the byte */ + line_parity ^= i; + line_parity_prime ^= ~i; + } + + } + + ecc_other->col_parity = (col_parity >> 2) & 0x3f; + ecc_other->line_parity = line_parity; + ecc_other->line_parity_prime = line_parity_prime; +} + +int yaffs_ecc_correct_other(unsigned char *data, unsigned n_bytes, + struct yaffs_ecc_other *read_ecc, + const struct yaffs_ecc_other *test_ecc) +{ + unsigned char delta_col; /* column parity delta */ + unsigned delta_line; /* line parity delta */ + unsigned delta_line_prime; /* line parity delta */ + unsigned bit; + + delta_col = read_ecc->col_parity ^ test_ecc->col_parity; + delta_line = read_ecc->line_parity ^ test_ecc->line_parity; + delta_line_prime = + read_ecc->line_parity_prime ^ test_ecc->line_parity_prime; + + if ((delta_col | delta_line | delta_line_prime) == 0) + return 0; /* no error */ + + if (delta_line == ~delta_line_prime && + (((delta_col ^ (delta_col >> 1)) & 0x15) == 0x15)) { + /* Single bit (recoverable) error in data */ + + bit = 0; + + if (delta_col & 0x20) + bit |= 0x04; + if (delta_col & 0x08) + bit |= 0x02; + if (delta_col & 0x02) + bit |= 0x01; + + if (delta_line >= n_bytes) + return -1; + + data[delta_line] ^= (1 << bit); + + return 1; /* corrected */ + } + + if ((hweight32(delta_line) + + hweight32(delta_line_prime) + + hweight8(delta_col)) == 1) { + /* Reccoverable error in ecc */ + + *read_ecc = *test_ecc; + return 1; /* corrected */ + } + + /* Unrecoverable error */ + + return -1; +} diff --git a/fs/yaffs2/yaffs_ecc.h b/fs/yaffs2/yaffs_ecc.h new file mode 100644 index 0000000..b0c461d --- /dev/null +++ b/fs/yaffs2/yaffs_ecc.h @@ -0,0 +1,44 @@ +/* + * YAFFS: Yet another Flash File System . A NAND-flash specific file system. + * + * Copyright (C) 2002-2010 Aleph One Ltd. + * for Toby Churchill Ltd and Brightstar Engineering + * + * Created by Charles Manning + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU Lesser General Public License version 2.1 as + * published by the Free Software Foundation. + * + * Note: Only YAFFS headers are LGPL, YAFFS C code is covered by GPL. + */ + +/* + * This code implements the ECC algorithm used in SmartMedia. + * + * The ECC comprises 22 bits of parity information and is stuffed into 3 bytes. + * The two unused bit are set to 1. + * The ECC can correct single bit errors in a 256-byte page of data. Thus, two such ECC + * blocks are used on a 512-byte NAND page. + * + */ + +#ifndef __YAFFS_ECC_H__ +#define __YAFFS_ECC_H__ + +struct yaffs_ecc_other { + unsigned char col_parity; + unsigned line_parity; + unsigned line_parity_prime; +}; + +void yaffs_ecc_cacl(const unsigned char *data, unsigned char *ecc); +int yaffs_ecc_correct(unsigned char *data, unsigned char *read_ecc, + const unsigned char *test_ecc); + +void yaffs_ecc_calc_other(const unsigned char *data, unsigned n_bytes, + struct yaffs_ecc_other *ecc); +int yaffs_ecc_correct_other(unsigned char *data, unsigned n_bytes, + struct yaffs_ecc_other *read_ecc, + const struct yaffs_ecc_other *test_ecc); +#endif -- 1.7.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/