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406 lines
11 KiB
406 lines
11 KiB
// SPDX-License-Identifier: GPL-2.0-or-later |
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/* |
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* This file provides ECC correction for more than 1 bit per block of data, |
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* using binary BCH codes. It relies on the generic BCH library lib/bch.c. |
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* |
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* Copyright © 2011 Ivan Djelic <[email protected]> |
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*/ |
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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/slab.h> |
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#include <linux/bitops.h> |
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#include <linux/mtd/nand.h> |
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#include <linux/mtd/nand-ecc-sw-bch.h> |
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/** |
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* nand_ecc_sw_bch_calculate - Calculate the ECC corresponding to a data block |
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* @nand: NAND device |
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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_ecc_sw_bch_calculate(struct nand_device *nand, |
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const unsigned char *buf, unsigned char *code) |
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{ |
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struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv; |
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unsigned int i; |
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memset(code, 0, engine_conf->code_size); |
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bch_encode(engine_conf->bch, buf, nand->ecc.ctx.conf.step_size, code); |
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/* apply mask so that an erased page is a valid codeword */ |
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for (i = 0; i < engine_conf->code_size; i++) |
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code[i] ^= engine_conf->eccmask[i]; |
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return 0; |
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} |
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EXPORT_SYMBOL(nand_ecc_sw_bch_calculate); |
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/** |
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* nand_ecc_sw_bch_correct - Detect, correct and report bit error(s) |
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* @nand: NAND device |
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* @buf: Raw data read from the chip |
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* @read_ecc: ECC bytes from the chip |
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* @calc_ecc: ECC calculated from the raw data |
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* |
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* Detect and correct bit errors for a data block. |
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*/ |
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int nand_ecc_sw_bch_correct(struct nand_device *nand, unsigned char *buf, |
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unsigned char *read_ecc, unsigned char *calc_ecc) |
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{ |
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struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv; |
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unsigned int step_size = nand->ecc.ctx.conf.step_size; |
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unsigned int *errloc = engine_conf->errloc; |
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int i, count; |
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count = bch_decode(engine_conf->bch, NULL, step_size, read_ecc, |
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calc_ecc, NULL, errloc); |
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if (count > 0) { |
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for (i = 0; i < count; i++) { |
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if (errloc[i] < (step_size * 8)) |
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/* The error is in the data area: correct it */ |
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buf[errloc[i] >> 3] ^= (1 << (errloc[i] & 7)); |
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/* Otherwise the error is in the ECC area: nothing to do */ |
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pr_debug("%s: corrected bitflip %u\n", __func__, |
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errloc[i]); |
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} |
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} else if (count < 0) { |
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pr_err("ECC unrecoverable error\n"); |
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count = -EBADMSG; |
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} |
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return count; |
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} |
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EXPORT_SYMBOL(nand_ecc_sw_bch_correct); |
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/** |
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* nand_ecc_sw_bch_cleanup - Cleanup software BCH ECC resources |
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* @nand: NAND device |
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*/ |
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static void nand_ecc_sw_bch_cleanup(struct nand_device *nand) |
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{ |
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struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv; |
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bch_free(engine_conf->bch); |
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kfree(engine_conf->errloc); |
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kfree(engine_conf->eccmask); |
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} |
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/** |
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* nand_ecc_sw_bch_init - Initialize software BCH ECC engine |
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* @nand: NAND device |
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* |
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* Returns: a pointer to a new NAND BCH control structure, or NULL upon failure |
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* |
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* Initialize NAND BCH error correction. @nand.ecc parameters 'step_size' and |
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* 'bytes' are used to compute the following BCH parameters: |
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* m, the Galois field order |
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* t, the error correction capability |
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* 'bytes' should be equal to the number of bytes required to store m * t |
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* bits, where m is such that 2^m - 1 > step_size * 8. |
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* |
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* Example: to configure 4 bit correction per 512 bytes, you should pass |
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* step_size = 512 (thus, m = 13 is the smallest integer such that 2^m - 1 > 512 * 8) |
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* bytes = 7 (7 bytes are required to store m * t = 13 * 4 = 52 bits) |
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*/ |
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static int nand_ecc_sw_bch_init(struct nand_device *nand) |
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{ |
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struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv; |
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unsigned int eccsize = nand->ecc.ctx.conf.step_size; |
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unsigned int eccbytes = engine_conf->code_size; |
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unsigned int m, t, i; |
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unsigned char *erased_page; |
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int ret; |
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m = fls(1 + (8 * eccsize)); |
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t = (eccbytes * 8) / m; |
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engine_conf->bch = bch_init(m, t, 0, false); |
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if (!engine_conf->bch) |
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return -EINVAL; |
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engine_conf->eccmask = kzalloc(eccbytes, GFP_KERNEL); |
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engine_conf->errloc = kmalloc_array(t, sizeof(*engine_conf->errloc), |
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GFP_KERNEL); |
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if (!engine_conf->eccmask || !engine_conf->errloc) { |
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ret = -ENOMEM; |
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goto cleanup; |
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} |
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/* Compute and store the inverted ECC of an erased step */ |
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erased_page = kmalloc(eccsize, GFP_KERNEL); |
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if (!erased_page) { |
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ret = -ENOMEM; |
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goto cleanup; |
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} |
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memset(erased_page, 0xff, eccsize); |
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bch_encode(engine_conf->bch, erased_page, eccsize, |
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engine_conf->eccmask); |
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kfree(erased_page); |
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for (i = 0; i < eccbytes; i++) |
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engine_conf->eccmask[i] ^= 0xff; |
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/* Verify that the number of code bytes has the expected value */ |
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if (engine_conf->bch->ecc_bytes != eccbytes) { |
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pr_err("Invalid number of ECC bytes: %u, expected: %u\n", |
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eccbytes, engine_conf->bch->ecc_bytes); |
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ret = -EINVAL; |
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goto cleanup; |
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} |
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/* Sanity checks */ |
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if (8 * (eccsize + eccbytes) >= (1 << m)) { |
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pr_err("ECC step size is too large (%u)\n", eccsize); |
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ret = -EINVAL; |
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goto cleanup; |
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} |
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return 0; |
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cleanup: |
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nand_ecc_sw_bch_cleanup(nand); |
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return ret; |
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} |
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int nand_ecc_sw_bch_init_ctx(struct nand_device *nand) |
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{ |
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struct nand_ecc_props *conf = &nand->ecc.ctx.conf; |
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struct mtd_info *mtd = nanddev_to_mtd(nand); |
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struct nand_ecc_sw_bch_conf *engine_conf; |
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unsigned int code_size = 0, nsteps; |
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int ret; |
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/* Only large page NAND chips may use BCH */ |
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if (mtd->oobsize < 64) { |
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pr_err("BCH cannot be used with small page NAND chips\n"); |
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return -EINVAL; |
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} |
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if (!mtd->ooblayout) |
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mtd_set_ooblayout(mtd, nand_get_large_page_ooblayout()); |
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conf->engine_type = NAND_ECC_ENGINE_TYPE_SOFT; |
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conf->algo = NAND_ECC_ALGO_BCH; |
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conf->step_size = nand->ecc.user_conf.step_size; |
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conf->strength = nand->ecc.user_conf.strength; |
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/* |
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* Board driver should supply ECC size and ECC strength |
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* values to select how many bits are correctable. |
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* Otherwise, default to 512 bytes for large page devices and 256 for |
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* small page devices. |
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*/ |
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if (!conf->step_size) { |
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if (mtd->oobsize >= 64) |
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conf->step_size = 512; |
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else |
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conf->step_size = 256; |
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conf->strength = 4; |
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} |
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nsteps = mtd->writesize / conf->step_size; |
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/* Maximize */ |
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if (nand->ecc.user_conf.flags & NAND_ECC_MAXIMIZE_STRENGTH) { |
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conf->step_size = 1024; |
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nsteps = mtd->writesize / conf->step_size; |
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/* Reserve 2 bytes for the BBM */ |
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code_size = (mtd->oobsize - 2) / nsteps; |
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conf->strength = code_size * 8 / fls(8 * conf->step_size); |
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} |
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if (!code_size) |
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code_size = DIV_ROUND_UP(conf->strength * |
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fls(8 * conf->step_size), 8); |
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if (!conf->strength) |
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conf->strength = (code_size * 8) / fls(8 * conf->step_size); |
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if (!code_size && !conf->strength) { |
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pr_err("Missing ECC parameters\n"); |
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return -EINVAL; |
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} |
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engine_conf = kzalloc(sizeof(*engine_conf), GFP_KERNEL); |
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if (!engine_conf) |
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return -ENOMEM; |
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ret = nand_ecc_init_req_tweaking(&engine_conf->req_ctx, nand); |
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if (ret) |
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goto free_engine_conf; |
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engine_conf->code_size = code_size; |
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engine_conf->nsteps = nsteps; |
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engine_conf->calc_buf = kzalloc(mtd->oobsize, GFP_KERNEL); |
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engine_conf->code_buf = kzalloc(mtd->oobsize, GFP_KERNEL); |
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if (!engine_conf->calc_buf || !engine_conf->code_buf) { |
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ret = -ENOMEM; |
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goto free_bufs; |
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} |
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nand->ecc.ctx.priv = engine_conf; |
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nand->ecc.ctx.total = nsteps * code_size; |
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ret = nand_ecc_sw_bch_init(nand); |
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if (ret) |
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goto free_bufs; |
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/* Verify the layout validity */ |
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if (mtd_ooblayout_count_eccbytes(mtd) != |
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engine_conf->nsteps * engine_conf->code_size) { |
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pr_err("Invalid ECC layout\n"); |
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ret = -EINVAL; |
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goto cleanup_bch_ctx; |
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} |
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return 0; |
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cleanup_bch_ctx: |
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nand_ecc_sw_bch_cleanup(nand); |
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free_bufs: |
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nand_ecc_cleanup_req_tweaking(&engine_conf->req_ctx); |
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kfree(engine_conf->calc_buf); |
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kfree(engine_conf->code_buf); |
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free_engine_conf: |
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kfree(engine_conf); |
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return ret; |
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} |
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EXPORT_SYMBOL(nand_ecc_sw_bch_init_ctx); |
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void nand_ecc_sw_bch_cleanup_ctx(struct nand_device *nand) |
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{ |
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struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv; |
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if (engine_conf) { |
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nand_ecc_sw_bch_cleanup(nand); |
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nand_ecc_cleanup_req_tweaking(&engine_conf->req_ctx); |
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kfree(engine_conf->calc_buf); |
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kfree(engine_conf->code_buf); |
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kfree(engine_conf); |
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} |
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} |
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EXPORT_SYMBOL(nand_ecc_sw_bch_cleanup_ctx); |
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static int nand_ecc_sw_bch_prepare_io_req(struct nand_device *nand, |
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struct nand_page_io_req *req) |
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{ |
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struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv; |
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struct mtd_info *mtd = nanddev_to_mtd(nand); |
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int eccsize = nand->ecc.ctx.conf.step_size; |
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int eccbytes = engine_conf->code_size; |
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int eccsteps = engine_conf->nsteps; |
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int total = nand->ecc.ctx.total; |
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u8 *ecccalc = engine_conf->calc_buf; |
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const u8 *data; |
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int i; |
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/* Nothing to do for a raw operation */ |
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if (req->mode == MTD_OPS_RAW) |
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return 0; |
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/* This engine does not provide BBM/free OOB bytes protection */ |
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if (!req->datalen) |
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return 0; |
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nand_ecc_tweak_req(&engine_conf->req_ctx, req); |
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/* No more preparation for page read */ |
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if (req->type == NAND_PAGE_READ) |
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return 0; |
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/* Preparation for page write: derive the ECC bytes and place them */ |
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for (i = 0, data = req->databuf.out; |
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eccsteps; |
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eccsteps--, i += eccbytes, data += eccsize) |
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nand_ecc_sw_bch_calculate(nand, data, &ecccalc[i]); |
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return mtd_ooblayout_set_eccbytes(mtd, ecccalc, (void *)req->oobbuf.out, |
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0, total); |
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} |
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static int nand_ecc_sw_bch_finish_io_req(struct nand_device *nand, |
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struct nand_page_io_req *req) |
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{ |
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struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv; |
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struct mtd_info *mtd = nanddev_to_mtd(nand); |
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int eccsize = nand->ecc.ctx.conf.step_size; |
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int total = nand->ecc.ctx.total; |
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int eccbytes = engine_conf->code_size; |
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int eccsteps = engine_conf->nsteps; |
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u8 *ecccalc = engine_conf->calc_buf; |
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u8 *ecccode = engine_conf->code_buf; |
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unsigned int max_bitflips = 0; |
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u8 *data = req->databuf.in; |
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int i, ret; |
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/* Nothing to do for a raw operation */ |
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if (req->mode == MTD_OPS_RAW) |
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return 0; |
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/* This engine does not provide BBM/free OOB bytes protection */ |
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if (!req->datalen) |
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return 0; |
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/* No more preparation for page write */ |
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if (req->type == NAND_PAGE_WRITE) { |
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nand_ecc_restore_req(&engine_conf->req_ctx, req); |
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return 0; |
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} |
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/* Finish a page read: retrieve the (raw) ECC bytes*/ |
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ret = mtd_ooblayout_get_eccbytes(mtd, ecccode, req->oobbuf.in, 0, |
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total); |
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if (ret) |
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return ret; |
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/* Calculate the ECC bytes */ |
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for (i = 0; eccsteps; eccsteps--, i += eccbytes, data += eccsize) |
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nand_ecc_sw_bch_calculate(nand, data, &ecccalc[i]); |
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/* Finish a page read: compare and correct */ |
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for (eccsteps = engine_conf->nsteps, i = 0, data = req->databuf.in; |
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eccsteps; |
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eccsteps--, i += eccbytes, data += eccsize) { |
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int stat = nand_ecc_sw_bch_correct(nand, data, |
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&ecccode[i], |
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&ecccalc[i]); |
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if (stat < 0) { |
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mtd->ecc_stats.failed++; |
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} else { |
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mtd->ecc_stats.corrected += stat; |
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max_bitflips = max_t(unsigned int, max_bitflips, stat); |
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} |
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} |
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nand_ecc_restore_req(&engine_conf->req_ctx, req); |
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return max_bitflips; |
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} |
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static struct nand_ecc_engine_ops nand_ecc_sw_bch_engine_ops = { |
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.init_ctx = nand_ecc_sw_bch_init_ctx, |
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.cleanup_ctx = nand_ecc_sw_bch_cleanup_ctx, |
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.prepare_io_req = nand_ecc_sw_bch_prepare_io_req, |
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.finish_io_req = nand_ecc_sw_bch_finish_io_req, |
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}; |
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static struct nand_ecc_engine nand_ecc_sw_bch_engine = { |
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.ops = &nand_ecc_sw_bch_engine_ops, |
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}; |
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struct nand_ecc_engine *nand_ecc_sw_bch_get_engine(void) |
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{ |
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return &nand_ecc_sw_bch_engine; |
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} |
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EXPORT_SYMBOL(nand_ecc_sw_bch_get_engine); |
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MODULE_LICENSE("GPL"); |
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MODULE_AUTHOR("Ivan Djelic <[email protected]>"); |
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MODULE_DESCRIPTION("NAND software BCH ECC support");
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