2 * This file provides ECC correction for more than 1 bit per block of data,
3 * using binary BCH codes. It relies on the generic BCH library lib/bch.c.
5 * Copyright © 2011 Ivan Djelic <ivan.djelic@parrot.com>
7 * SPDX-License-Identifier: GPL-2.0+
11 /*#include <asm/io.h>*/
12 #include <linux/types.h>
14 #include <linux/bitops.h>
15 #include <linux/mtd/mtd.h>
16 #include <linux/mtd/nand.h>
17 #include <linux/mtd/nand_bch.h>
18 #include <linux/bch.h>
22 * struct nand_bch_control - private NAND BCH control structure
23 * @bch: BCH control structure
24 * @ecclayout: private ecc layout for this BCH configuration
25 * @errloc: error location array
26 * @eccmask: XOR ecc mask, allows erased pages to be decoded as valid
28 struct nand_bch_control {
29 struct bch_control *bch;
30 struct nand_ecclayout ecclayout;
32 unsigned char *eccmask;
36 * nand_bch_calculate_ecc - [NAND Interface] Calculate ECC for data block
37 * @mtd: MTD block structure
38 * @buf: input buffer with raw data
39 * @code: output buffer with ECC
41 int nand_bch_calculate_ecc(struct mtd_info *mtd, const unsigned char *buf,
44 const struct nand_chip *chip = mtd->priv;
45 struct nand_bch_control *nbc = chip->ecc.priv;
48 memset(code, 0, chip->ecc.bytes);
49 encode_bch(nbc->bch, buf, chip->ecc.size, code);
51 /* apply mask so that an erased page is a valid codeword */
52 for (i = 0; i < chip->ecc.bytes; i++)
53 code[i] ^= nbc->eccmask[i];
59 * nand_bch_correct_data - [NAND Interface] Detect and correct bit error(s)
60 * @mtd: MTD block structure
61 * @buf: raw data read from the chip
62 * @read_ecc: ECC from the chip
63 * @calc_ecc: the ECC calculated from raw data
65 * Detect and correct bit errors for a data byte block
67 int nand_bch_correct_data(struct mtd_info *mtd, unsigned char *buf,
68 unsigned char *read_ecc, unsigned char *calc_ecc)
70 const struct nand_chip *chip = mtd->priv;
71 struct nand_bch_control *nbc = chip->ecc.priv;
72 unsigned int *errloc = nbc->errloc;
75 count = decode_bch(nbc->bch, NULL, chip->ecc.size, read_ecc, calc_ecc,
78 for (i = 0; i < count; i++) {
79 if (errloc[i] < (chip->ecc.size*8))
80 /* error is located in data, correct it */
81 buf[errloc[i] >> 3] ^= (1 << (errloc[i] & 7));
82 /* else error in ecc, no action needed */
84 MTDDEBUG(MTD_DEBUG_LEVEL0, "%s: corrected bitflip %u\n",
87 } else if (count < 0) {
88 printk(KERN_ERR "ecc unrecoverable error\n");
95 * nand_bch_init - [NAND Interface] Initialize NAND BCH error correction
96 * @mtd: MTD block structure
97 * @eccsize: ecc block size in bytes
98 * @eccbytes: ecc length in bytes
99 * @ecclayout: output default layout
102 * a pointer to a new NAND BCH control structure, or NULL upon failure
104 * Initialize NAND BCH error correction. Parameters @eccsize and @eccbytes
105 * are used to compute BCH parameters m (Galois field order) and t (error
106 * correction capability). @eccbytes should be equal to the number of bytes
107 * required to store m*t bits, where m is such that 2^m-1 > @eccsize*8.
109 * Example: to configure 4 bit correction per 512 bytes, you should pass
110 * @eccsize = 512 (thus, m=13 is the smallest integer such that 2^m-1 > 512*8)
111 * @eccbytes = 7 (7 bytes are required to store m*t = 13*4 = 52 bits)
113 struct nand_bch_control *
114 nand_bch_init(struct mtd_info *mtd, unsigned int eccsize, unsigned int eccbytes,
115 struct nand_ecclayout **ecclayout)
117 unsigned int m, t, eccsteps, i;
118 struct nand_ecclayout *layout;
119 struct nand_bch_control *nbc = NULL;
120 unsigned char *erased_page;
122 if (!eccsize || !eccbytes) {
123 printk(KERN_WARNING "ecc parameters not supplied\n");
127 m = fls(1+8*eccsize);
130 nbc = kzalloc(sizeof(*nbc), GFP_KERNEL);
134 nbc->bch = init_bch(m, t, 0);
138 /* verify that eccbytes has the expected value */
139 if (nbc->bch->ecc_bytes != eccbytes) {
140 printk(KERN_WARNING "invalid eccbytes %u, should be %u\n",
141 eccbytes, nbc->bch->ecc_bytes);
145 eccsteps = mtd->writesize/eccsize;
147 /* if no ecc placement scheme was provided, build one */
150 /* handle large page devices only */
151 if (mtd->oobsize < 64) {
152 printk(KERN_WARNING "must provide an oob scheme for "
153 "oobsize %d\n", mtd->oobsize);
157 layout = &nbc->ecclayout;
158 layout->eccbytes = eccsteps*eccbytes;
160 /* reserve 2 bytes for bad block marker */
161 if (layout->eccbytes+2 > mtd->oobsize) {
162 printk(KERN_WARNING "no suitable oob scheme available "
163 "for oobsize %d eccbytes %u\n", mtd->oobsize,
167 /* put ecc bytes at oob tail */
168 for (i = 0; i < layout->eccbytes; i++)
169 layout->eccpos[i] = mtd->oobsize-layout->eccbytes+i;
171 layout->oobfree[0].offset = 2;
172 layout->oobfree[0].length = mtd->oobsize-2-layout->eccbytes;
178 if (8*(eccsize+eccbytes) >= (1 << m)) {
179 printk(KERN_WARNING "eccsize %u is too large\n", eccsize);
182 if ((*ecclayout)->eccbytes != (eccsteps*eccbytes)) {
183 printk(KERN_WARNING "invalid ecc layout\n");
187 nbc->eccmask = kmalloc(eccbytes, GFP_KERNEL);
188 nbc->errloc = kmalloc(t*sizeof(*nbc->errloc), GFP_KERNEL);
189 if (!nbc->eccmask || !nbc->errloc)
192 * compute and store the inverted ecc of an erased ecc block
194 erased_page = kmalloc(eccsize, GFP_KERNEL);
198 memset(erased_page, 0xff, eccsize);
199 memset(nbc->eccmask, 0, eccbytes);
200 encode_bch(nbc->bch, erased_page, eccsize, nbc->eccmask);
203 for (i = 0; i < eccbytes; i++)
204 nbc->eccmask[i] ^= 0xff;
213 * nand_bch_free - [NAND Interface] Release NAND BCH ECC resources
214 * @nbc: NAND BCH control structure
216 void nand_bch_free(struct nand_bch_control *nbc)