1 // SPDX-License-Identifier: GPL-2.0+ 2 /* 3 * This file provides ECC correction for more than 1 bit per block of data, 4 * using binary BCH codes. It relies on the generic BCH library lib/bch.c. 5 * 6 * Copyright © 2011 Ivan Djelic <ivan.djelic@parrot.com> 7 * 8 */ 9 10 #include <common.h> 11 /*#include <asm/io.h>*/ 12 #include <linux/types.h> 13 14 #include <linux/bitops.h> 15 #include <linux/mtd/mtd.h> 16 #include <linux/mtd/rawnand.h> 17 #include <linux/mtd/nand_bch.h> 18 #include <linux/bch.h> 19 #include <malloc.h> 20 21 /** 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 27 */ 28 struct nand_bch_control { 29 struct bch_control *bch; 30 struct nand_ecclayout ecclayout; 31 unsigned int *errloc; 32 unsigned char *eccmask; 33 }; 34 35 /** 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 40 */ 41 int nand_bch_calculate_ecc(struct mtd_info *mtd, const unsigned char *buf, 42 unsigned char *code) 43 { 44 const struct nand_chip *chip = mtd_to_nand(mtd); 45 struct nand_bch_control *nbc = chip->ecc.priv; 46 unsigned int i; 47 48 memset(code, 0, chip->ecc.bytes); 49 encode_bch(nbc->bch, buf, chip->ecc.size, code); 50 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]; 54 55 return 0; 56 } 57 58 /** 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 64 * 65 * Detect and correct bit errors for a data byte block 66 */ 67 int nand_bch_correct_data(struct mtd_info *mtd, unsigned char *buf, 68 unsigned char *read_ecc, unsigned char *calc_ecc) 69 { 70 const struct nand_chip *chip = mtd_to_nand(mtd); 71 struct nand_bch_control *nbc = chip->ecc.priv; 72 unsigned int *errloc = nbc->errloc; 73 int i, count; 74 75 count = decode_bch(nbc->bch, NULL, chip->ecc.size, read_ecc, calc_ecc, 76 NULL, errloc); 77 if (count > 0) { 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 */ 83 84 pr_debug("%s: corrected bitflip %u\n", 85 __func__, errloc[i]); 86 } 87 } else if (count < 0) { 88 printk(KERN_ERR "ecc unrecoverable error\n"); 89 count = -EBADMSG; 90 } 91 return count; 92 } 93 94 /** 95 * nand_bch_init - [NAND Interface] Initialize NAND BCH error correction 96 * @mtd: MTD block structure 97 * 98 * Returns: 99 * a pointer to a new NAND BCH control structure, or NULL upon failure 100 * 101 * Initialize NAND BCH error correction. Parameters @eccsize and @eccbytes 102 * are used to compute BCH parameters m (Galois field order) and t (error 103 * correction capability). @eccbytes should be equal to the number of bytes 104 * required to store m*t bits, where m is such that 2^m-1 > @eccsize*8. 105 * 106 * Example: to configure 4 bit correction per 512 bytes, you should pass 107 * @eccsize = 512 (thus, m=13 is the smallest integer such that 2^m-1 > 512*8) 108 * @eccbytes = 7 (7 bytes are required to store m*t = 13*4 = 52 bits) 109 */ 110 struct nand_bch_control *nand_bch_init(struct mtd_info *mtd) 111 { 112 struct nand_chip *nand = mtd_to_nand(mtd); 113 unsigned int m, t, eccsteps, i; 114 struct nand_ecclayout *layout = nand->ecc.layout; 115 struct nand_bch_control *nbc = NULL; 116 unsigned char *erased_page; 117 unsigned int eccsize = nand->ecc.size; 118 unsigned int eccbytes = nand->ecc.bytes; 119 unsigned int eccstrength = nand->ecc.strength; 120 121 if (!eccbytes && eccstrength) { 122 eccbytes = DIV_ROUND_UP(eccstrength * fls(8 * eccsize), 8); 123 nand->ecc.bytes = eccbytes; 124 } 125 126 if (!eccsize || !eccbytes) { 127 printk(KERN_WARNING "ecc parameters not supplied\n"); 128 goto fail; 129 } 130 131 m = fls(1+8*eccsize); 132 t = (eccbytes*8)/m; 133 134 nbc = kzalloc(sizeof(*nbc), GFP_KERNEL); 135 if (!nbc) 136 goto fail; 137 138 nbc->bch = init_bch(m, t, 0); 139 if (!nbc->bch) 140 goto fail; 141 142 /* verify that eccbytes has the expected value */ 143 if (nbc->bch->ecc_bytes != eccbytes) { 144 printk(KERN_WARNING "invalid eccbytes %u, should be %u\n", 145 eccbytes, nbc->bch->ecc_bytes); 146 goto fail; 147 } 148 149 eccsteps = mtd->writesize/eccsize; 150 151 /* if no ecc placement scheme was provided, build one */ 152 if (!layout) { 153 154 /* handle large page devices only */ 155 if (mtd->oobsize < 64) { 156 printk(KERN_WARNING "must provide an oob scheme for " 157 "oobsize %d\n", mtd->oobsize); 158 goto fail; 159 } 160 161 layout = &nbc->ecclayout; 162 layout->eccbytes = eccsteps*eccbytes; 163 164 /* reserve 2 bytes for bad block marker */ 165 if (layout->eccbytes+2 > mtd->oobsize) { 166 printk(KERN_WARNING "no suitable oob scheme available " 167 "for oobsize %d eccbytes %u\n", mtd->oobsize, 168 eccbytes); 169 goto fail; 170 } 171 /* put ecc bytes at oob tail */ 172 for (i = 0; i < layout->eccbytes; i++) 173 layout->eccpos[i] = mtd->oobsize-layout->eccbytes+i; 174 175 layout->oobfree[0].offset = 2; 176 layout->oobfree[0].length = mtd->oobsize-2-layout->eccbytes; 177 178 nand->ecc.layout = layout; 179 } 180 181 /* sanity checks */ 182 if (8*(eccsize+eccbytes) >= (1 << m)) { 183 printk(KERN_WARNING "eccsize %u is too large\n", eccsize); 184 goto fail; 185 } 186 if (layout->eccbytes != (eccsteps*eccbytes)) { 187 printk(KERN_WARNING "invalid ecc layout\n"); 188 goto fail; 189 } 190 191 nbc->eccmask = kmalloc(eccbytes, GFP_KERNEL); 192 nbc->errloc = kmalloc(t*sizeof(*nbc->errloc), GFP_KERNEL); 193 if (!nbc->eccmask || !nbc->errloc) 194 goto fail; 195 /* 196 * compute and store the inverted ecc of an erased ecc block 197 */ 198 erased_page = kmalloc(eccsize, GFP_KERNEL); 199 if (!erased_page) 200 goto fail; 201 202 memset(erased_page, 0xff, eccsize); 203 memset(nbc->eccmask, 0, eccbytes); 204 encode_bch(nbc->bch, erased_page, eccsize, nbc->eccmask); 205 kfree(erased_page); 206 207 for (i = 0; i < eccbytes; i++) 208 nbc->eccmask[i] ^= 0xff; 209 210 if (!eccstrength) 211 nand->ecc.strength = (eccbytes * 8) / fls(8 * eccsize); 212 213 return nbc; 214 fail: 215 nand_bch_free(nbc); 216 return NULL; 217 } 218 219 /** 220 * nand_bch_free - [NAND Interface] Release NAND BCH ECC resources 221 * @nbc: NAND BCH control structure 222 */ 223 void nand_bch_free(struct nand_bch_control *nbc) 224 { 225 if (nbc) { 226 free_bch(nbc->bch); 227 kfree(nbc->errloc); 228 kfree(nbc->eccmask); 229 kfree(nbc); 230 } 231 } 232