1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
|
/*
* This file provides ECC correction for more than 1 bit per block of data,
* using binary BCH codes. It relies on the generic BCH library lib/bch.c.
*
* Copyright © 2011 Ivan Djelic <ivan.djelic@parrot.com>
*
* This file is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation; either version 2 or (at your option) any
* later version.
*
* This file is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* for more details.
*
* You should have received a copy of the GNU General Public License along
* with this file; if not, write to the Free Software Foundation, Inc.,
* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
*/
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/bitops.h>
#include <linux/mtd/mtd.h>
#include <linux/mtd/nand.h>
#include <linux/mtd/nand_bch.h>
#include <linux/bch.h>
/**
* struct nand_bch_control - private NAND BCH control structure
* @bch: BCH control structure
* @ecclayout: private ecc layout for this BCH configuration
* @errloc: error location array
* @eccmask: XOR ecc mask, allows erased pages to be decoded as valid
*/
struct nand_bch_control {
struct bch_control *bch;
struct nand_ecclayout ecclayout;
unsigned int *errloc;
unsigned char *eccmask;
};
/**
* nand_bch_calculate_ecc - [NAND Interface] Calculate ECC for data block
* @mtd: MTD block structure
* @buf: input buffer with raw data
* @code: output buffer with ECC
*/
int nand_bch_calculate_ecc(struct mtd_info *mtd, const unsigned char *buf,
unsigned char *code)
{
const struct nand_chip *chip = mtd->priv;
struct nand_bch_control *nbc = chip->ecc.priv;
unsigned int i;
memset(code, 0, chip->ecc.bytes);
encode_bch(nbc->bch, buf, chip->ecc.size, code);
/* apply mask so that an erased page is a valid codeword */
for (i = 0; i < chip->ecc.bytes; i++)
code[i] ^= nbc->eccmask[i];
return 0;
}
EXPORT_SYMBOL(nand_bch_calculate_ecc);
/**
* nand_bch_correct_data - [NAND Interface] Detect and correct bit error(s)
* @mtd: MTD block structure
* @buf: raw data read from the chip
* @read_ecc: ECC from the chip
* @calc_ecc: the ECC calculated from raw data
*
* Detect and correct bit errors for a data byte block
*/
int nand_bch_correct_data(struct mtd_info *mtd, unsigned char *buf,
unsigned char *read_ecc, unsigned char *calc_ecc)
{
const struct nand_chip *chip = mtd->priv;
struct nand_bch_control *nbc = chip->ecc.priv;
unsigned int *errloc = nbc->errloc;
int i, count;
count = decode_bch(nbc->bch, NULL, chip->ecc.size, read_ecc, calc_ecc,
NULL, errloc);
if (count > 0) {
for (i = 0; i < count; i++) {
if (errloc[i] < (chip->ecc.size*8))
/* error is located in data, correct it */
buf[errloc[i] >> 3] ^= (1 << (errloc[i] & 7));
/* else error in ecc, no action needed */
pr_debug("%s: corrected bitflip %u\n", __func__,
errloc[i]);
}
} else if (count < 0) {
printk(KERN_ERR "ecc unrecoverable error\n");
count = -1;
}
return count;
}
EXPORT_SYMBOL(nand_bch_correct_data);
/**
* nand_bch_init - [NAND Interface] Initialize NAND BCH error correction
* @mtd: MTD block structure
* @eccsize: ecc block size in bytes
* @eccbytes: ecc length in bytes
* @ecclayout: output default layout
*
* Returns:
* a pointer to a new NAND BCH control structure, or NULL upon failure
*
* Initialize NAND BCH error correction. Parameters @eccsize and @eccbytes
* are used to compute BCH parameters m (Galois field order) and t (error
* correction capability). @eccbytes should be equal to the number of bytes
* required to store m*t bits, where m is such that 2^m-1 > @eccsize*8.
*
* Example: to configure 4 bit correction per 512 bytes, you should pass
* @eccsize = 512 (thus, m=13 is the smallest integer such that 2^m-1 > 512*8)
* @eccbytes = 7 (7 bytes are required to store m*t = 13*4 = 52 bits)
*/
struct nand_bch_control *
nand_bch_init(struct mtd_info *mtd, unsigned int eccsize, unsigned int eccbytes,
struct nand_ecclayout **ecclayout)
{
unsigned int m, t, eccsteps, i;
struct nand_ecclayout *layout;
struct nand_bch_control *nbc = NULL;
unsigned char *erased_page;
if (!eccsize || !eccbytes) {
printk(KERN_WARNING "ecc parameters not supplied\n");
goto fail;
}
m = fls(1+8*eccsize);
t = (eccbytes*8)/m;
nbc = kzalloc(sizeof(*nbc), GFP_KERNEL);
if (!nbc)
goto fail;
nbc->bch = init_bch(m, t, 0);
if (!nbc->bch)
goto fail;
/* verify that eccbytes has the expected value */
if (nbc->bch->ecc_bytes != eccbytes) {
printk(KERN_WARNING "invalid eccbytes %u, should be %u\n",
eccbytes, nbc->bch->ecc_bytes);
goto fail;
}
eccsteps = mtd->writesize/eccsize;
/* if no ecc placement scheme was provided, build one */
if (!*ecclayout) {
/* handle large page devices only */
if (mtd->oobsize < 64) {
printk(KERN_WARNING "must provide an oob scheme for "
"oobsize %d\n", mtd->oobsize);
goto fail;
}
layout = &nbc->ecclayout;
layout->eccbytes = eccsteps*eccbytes;
/* reserve 2 bytes for bad block marker */
if (layout->eccbytes+2 > mtd->oobsize) {
printk(KERN_WARNING "no suitable oob scheme available "
"for oobsize %d eccbytes %u\n", mtd->oobsize,
eccbytes);
goto fail;
}
/* put ecc bytes at oob tail */
for (i = 0; i < layout->eccbytes; i++)
layout->eccpos[i] = mtd->oobsize-layout->eccbytes+i;
layout->oobfree[0].offset = 2;
layout->oobfree[0].length = mtd->oobsize-2-layout->eccbytes;
*ecclayout = layout;
}
/* sanity checks */
if (8*(eccsize+eccbytes) >= (1 << m)) {
printk(KERN_WARNING "eccsize %u is too large\n", eccsize);
goto fail;
}
if ((*ecclayout)->eccbytes != (eccsteps*eccbytes)) {
printk(KERN_WARNING "invalid ecc layout\n");
goto fail;
}
nbc->eccmask = kmalloc(eccbytes, GFP_KERNEL);
nbc->errloc = kmalloc(t*sizeof(*nbc->errloc), GFP_KERNEL);
if (!nbc->eccmask || !nbc->errloc)
goto fail;
/*
* compute and store the inverted ecc of an erased ecc block
*/
erased_page = kmalloc(eccsize, GFP_KERNEL);
if (!erased_page)
goto fail;
memset(erased_page, 0xff, eccsize);
memset(nbc->eccmask, 0, eccbytes);
encode_bch(nbc->bch, erased_page, eccsize, nbc->eccmask);
kfree(erased_page);
for (i = 0; i < eccbytes; i++)
nbc->eccmask[i] ^= 0xff;
return nbc;
fail:
nand_bch_free(nbc);
return NULL;
}
EXPORT_SYMBOL(nand_bch_init);
/**
* nand_bch_free - [NAND Interface] Release NAND BCH ECC resources
* @nbc: NAND BCH control structure
*/
void nand_bch_free(struct nand_bch_control *nbc)
{
if (nbc) {
free_bch(nbc->bch);
kfree(nbc->errloc);
kfree(nbc->eccmask);
kfree(nbc);
}
}
EXPORT_SYMBOL(nand_bch_free);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Ivan Djelic <ivan.djelic@parrot.com>");
MODULE_DESCRIPTION("NAND software BCH ECC support");
|
