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![Miquel Raynal](/assets/img/avatar_default.png)
The software BCH ECC engine stores the nsteps variable in its own private structure while it is also exported as a public ECC field. Let's get rid of the redundant private one and let's use the nand_ecc_context structure when possible. Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com> Tested-by: Adam Ford <aford173@gmail.com> #logicpd Torpedo Link: https://lore.kernel.org/linux-mtd/20210127203020.9574-9-miquel.raynal@bootlin.com
406 lines
11 KiB
C
406 lines
11 KiB
C
// 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 <ivan.djelic@parrot.com>
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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->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.nsteps = nsteps;
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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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nand->ecc.ctx.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 = nand->ecc.ctx.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 = nand->ecc.ctx.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 = nand->ecc.ctx.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 <ivan.djelic@parrot.com>");
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MODULE_DESCRIPTION("NAND software BCH ECC support");
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