1 files changed, 406 insertions, 0 deletions
diff --git a/drivers/mtd/nand/ecc-sw-bch.c b/drivers/mtd/nand/ecc-sw-bch.c
new file mode 100644
index 000000000000..0a0ac11d5725
--- /dev/null
+++ b/drivers/mtd/nand/ecc-sw-bch.c
@@ -0,0 +1,406 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * 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>
+ */
+
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/bitops.h>
+#include <linux/mtd/nand.h>
+#include <linux/mtd/nand-ecc-sw-bch.h>
+
+/**
+ * nand_ecc_sw_bch_calculate - Calculate the ECC corresponding to a data block
+ * @nand: NAND device
+ * @buf: Input buffer with raw data
+ * @code: Output buffer with ECC
+ */
+int nand_ecc_sw_bch_calculate(struct nand_device *nand,
+			      const unsigned char *buf, unsigned char *code)
+{
+	struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv;
+	unsigned int i;
+
+	memset(code, 0, engine_conf->code_size);
+	bch_encode(engine_conf->bch, buf, nand->ecc.ctx.conf.step_size, code);
+
+	/* apply mask so that an erased page is a valid codeword */
+	for (i = 0; i < engine_conf->code_size; i++)
+		code[i] ^= engine_conf->eccmask[i];
+
+	return 0;
+}
+EXPORT_SYMBOL(nand_ecc_sw_bch_calculate);
+
+/**
+ * nand_ecc_sw_bch_correct - Detect, correct and report bit error(s)
+ * @nand: NAND device
+ * @buf: Raw data read from the chip
+ * @read_ecc: ECC bytes from the chip
+ * @calc_ecc: ECC calculated from the raw data
+ *
+ * Detect and correct bit errors for a data block.
+ */
+int nand_ecc_sw_bch_correct(struct nand_device *nand, unsigned char *buf,
+			    unsigned char *read_ecc, unsigned char *calc_ecc)
+{
+	struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv;
+	unsigned int step_size = nand->ecc.ctx.conf.step_size;
+	unsigned int *errloc = engine_conf->errloc;
+	int i, count;
+
+	count = bch_decode(engine_conf->bch, NULL, step_size, read_ecc,
+			   calc_ecc, NULL, errloc);
+	if (count > 0) {
+		for (i = 0; i < count; i++) {
+			if (errloc[i] < (step_size * 8))
+				/* The error is in the data area: correct it */
+				buf[errloc[i] >> 3] ^= (1 << (errloc[i] & 7));
+
+			/* Otherwise the error is in the ECC area: nothing to do */
+			pr_debug("%s: corrected bitflip %u\n", __func__,
+				 errloc[i]);
+		}
+	} else if (count < 0) {
+		pr_err("ECC unrecoverable error\n");
+		count = -EBADMSG;
+	}
+
+	return count;
+}
+EXPORT_SYMBOL(nand_ecc_sw_bch_correct);
+
+/**
+ * nand_ecc_sw_bch_cleanup - Cleanup software BCH ECC resources
+ * @nand: NAND device
+ */
+static void nand_ecc_sw_bch_cleanup(struct nand_device *nand)
+{
+	struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv;
+
+	bch_free(engine_conf->bch);
+	kfree(engine_conf->errloc);
+	kfree(engine_conf->eccmask);
+}
+
+/**
+ * nand_ecc_sw_bch_init - Initialize software BCH ECC engine
+ * @nand: NAND device
+ *
+ * Returns: a pointer to a new NAND BCH control structure, or NULL upon failure
+ *
+ * Initialize NAND BCH error correction. @nand.ecc parameters 'step_size' and
+ * 'bytes' are used to compute the following BCH parameters:
+ *     m, the Galois field order
+ *     t, the error correction capability
+ * 'bytes' should be equal to the number of bytes required to store m * t
+ * bits, where m is such that 2^m - 1 > step_size * 8.
+ *
+ * Example: to configure 4 bit correction per 512 bytes, you should pass
+ * step_size = 512 (thus, m = 13 is the smallest integer such that 2^m - 1 > 512 * 8)
+ * bytes = 7 (7 bytes are required to store m * t = 13 * 4 = 52 bits)
+ */
+static int nand_ecc_sw_bch_init(struct nand_device *nand)
+{
+	struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv;
+	unsigned int eccsize = nand->ecc.ctx.conf.step_size;
+	unsigned int eccbytes = engine_conf->code_size;
+	unsigned int m, t, i;
+	unsigned char *erased_page;
+	int ret;
+
+	m = fls(1 + (8 * eccsize));
+	t = (eccbytes * 8) / m;
+
+	engine_conf->bch = bch_init(m, t, 0, false);
+	if (!engine_conf->bch)
+		return -EINVAL;
+
+	engine_conf->eccmask = kzalloc(eccbytes, GFP_KERNEL);
+	engine_conf->errloc = kmalloc_array(t, sizeof(*engine_conf->errloc),
+					    GFP_KERNEL);
+	if (!engine_conf->eccmask || !engine_conf->errloc) {
+		ret = -ENOMEM;
+		goto cleanup;
+	}
+
+	/* Compute and store the inverted ECC of an erased step */
+	erased_page = kmalloc(eccsize, GFP_KERNEL);
+	if (!erased_page) {
+		ret = -ENOMEM;
+		goto cleanup;
+	}
+
+	memset(erased_page, 0xff, eccsize);
+	bch_encode(engine_conf->bch, erased_page, eccsize,
+		   engine_conf->eccmask);
+	kfree(erased_page);
+
+	for (i = 0; i < eccbytes; i++)
+		engine_conf->eccmask[i] ^= 0xff;
+
+	/* Verify that the number of code bytes has the expected value */
+	if (engine_conf->bch->ecc_bytes != eccbytes) {
+		pr_err("Invalid number of ECC bytes: %u, expected: %u\n",
+		       eccbytes, engine_conf->bch->ecc_bytes);
+		ret = -EINVAL;
+		goto cleanup;
+	}
+
+	/* Sanity checks */
+	if (8 * (eccsize + eccbytes) >= (1 << m)) {
+		pr_err("ECC step size is too large (%u)\n", eccsize);
+		ret = -EINVAL;
+		goto cleanup;
+	}
+
+	return 0;
+
+cleanup:
+	nand_ecc_sw_bch_cleanup(nand);
+
+	return ret;
+}
+
+int nand_ecc_sw_bch_init_ctx(struct nand_device *nand)
+{
+	struct nand_ecc_props *conf = &nand->ecc.ctx.conf;
+	struct mtd_info *mtd = nanddev_to_mtd(nand);
+	struct nand_ecc_sw_bch_conf *engine_conf;
+	unsigned int code_size = 0, nsteps;
+	int ret;
+
+	/* Only large page NAND chips may use BCH */
+	if (mtd->oobsize < 64) {
+		pr_err("BCH cannot be used with small page NAND chips\n");
+		return -EINVAL;
+	}
+
+	if (!mtd->ooblayout)
+		mtd_set_ooblayout(mtd, nand_get_large_page_ooblayout());
+
+	conf->engine_type = NAND_ECC_ENGINE_TYPE_SOFT;
+	conf->algo = NAND_ECC_ALGO_BCH;
+	conf->step_size = nand->ecc.user_conf.step_size;
+	conf->strength = nand->ecc.user_conf.strength;
+
+	/*
+	 * Board driver should supply ECC size and ECC strength
+	 * values to select how many bits are correctable.
+	 * Otherwise, default to 512 bytes for large page devices and 256 for
+	 * small page devices.
+	 */
+	if (!conf->step_size) {
+		if (mtd->oobsize >= 64)
+			conf->step_size = 512;
+		else
+			conf->step_size = 256;
+
+		conf->strength = 4;
+	}
+
+	nsteps = mtd->writesize / conf->step_size;
+
+	/* Maximize */
+	if (nand->ecc.user_conf.flags & NAND_ECC_MAXIMIZE_STRENGTH) {
+		conf->step_size = 1024;
+		nsteps = mtd->writesize / conf->step_size;
+		/* Reserve 2 bytes for the BBM */
+		code_size = (mtd->oobsize - 2) / nsteps;
+		conf->strength = code_size * 8 / fls(8 * conf->step_size);
+	}
+
+	if (!code_size)
+		code_size = DIV_ROUND_UP(conf->strength *
+					 fls(8 * conf->step_size), 8);
+
+	if (!conf->strength)
+		conf->strength = (code_size * 8) / fls(8 * conf->step_size);
+
+	if (!code_size && !conf->strength) {
+		pr_err("Missing ECC parameters\n");
+		return -EINVAL;
+	}
+
+	engine_conf = kzalloc(sizeof(*engine_conf), GFP_KERNEL);
+	if (!engine_conf)
+		return -ENOMEM;
+
+	ret = nand_ecc_init_req_tweaking(&engine_conf->req_ctx, nand);
+	if (ret)
+		goto free_engine_conf;
+
+	engine_conf->code_size = code_size;
+	engine_conf->nsteps = nsteps;
+	engine_conf->calc_buf = kzalloc(mtd->oobsize, GFP_KERNEL);
+	engine_conf->code_buf = kzalloc(mtd->oobsize, GFP_KERNEL);
+	if (!engine_conf->calc_buf || !engine_conf->code_buf) {
+		ret = -ENOMEM;
+		goto free_bufs;
+	}
+
+	nand->ecc.ctx.priv = engine_conf;
+	nand->ecc.ctx.total = nsteps * code_size;
+
+	ret = nand_ecc_sw_bch_init(nand);
+	if (ret)
+		goto free_bufs;
+
+	/* Verify the layout validity */
+	if (mtd_ooblayout_count_eccbytes(mtd) !=
+	    engine_conf->nsteps * engine_conf->code_size) {
+		pr_err("Invalid ECC layout\n");
+		ret = -EINVAL;
+		goto cleanup_bch_ctx;
+	}
+
+	return 0;
+
+cleanup_bch_ctx:
+	nand_ecc_sw_bch_cleanup(nand);
+free_bufs:
+	nand_ecc_cleanup_req_tweaking(&engine_conf->req_ctx);
+	kfree(engine_conf->calc_buf);
+	kfree(engine_conf->code_buf);
+free_engine_conf:
+	kfree(engine_conf);
+
+	return ret;
+}
+EXPORT_SYMBOL(nand_ecc_sw_bch_init_ctx);
+
+void nand_ecc_sw_bch_cleanup_ctx(struct nand_device *nand)
+{
+	struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv;
+
+	if (engine_conf) {
+		nand_ecc_sw_bch_cleanup(nand);
+		nand_ecc_cleanup_req_tweaking(&engine_conf->req_ctx);
+		kfree(engine_conf->calc_buf);
+		kfree(engine_conf->code_buf);
+		kfree(engine_conf);
+	}
+}
+EXPORT_SYMBOL(nand_ecc_sw_bch_cleanup_ctx);
+
+static int nand_ecc_sw_bch_prepare_io_req(struct nand_device *nand,
+					  struct nand_page_io_req *req)
+{
+	struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv;
+	struct mtd_info *mtd = nanddev_to_mtd(nand);
+	int eccsize = nand->ecc.ctx.conf.step_size;
+	int eccbytes = engine_conf->code_size;
+	int eccsteps = engine_conf->nsteps;
+	int total = nand->ecc.ctx.total;
+	u8 *ecccalc = engine_conf->calc_buf;
+	const u8 *data;
+	int i;
+
+	/* Nothing to do for a raw operation */
+	if (req->mode == MTD_OPS_RAW)
+		return 0;
+
+	/* This engine does not provide BBM/free OOB bytes protection */
+	if (!req->datalen)
+		return 0;
+
+	nand_ecc_tweak_req(&engine_conf->req_ctx, req);
+
+	/* No more preparation for page read */
+	if (req->type == NAND_PAGE_READ)
+		return 0;
+
+	/* Preparation for page write: derive the ECC bytes and place them */
+	for (i = 0, data = req->databuf.out;
+	     eccsteps;
+	     eccsteps--, i += eccbytes, data += eccsize)
+		nand_ecc_sw_bch_calculate(nand, data, &ecccalc[i]);
+
+	return mtd_ooblayout_set_eccbytes(mtd, ecccalc, (void *)req->oobbuf.out,
+					  0, total);
+}
+
+static int nand_ecc_sw_bch_finish_io_req(struct nand_device *nand,
+					 struct nand_page_io_req *req)
+{
+	struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv;
+	struct mtd_info *mtd = nanddev_to_mtd(nand);
+	int eccsize = nand->ecc.ctx.conf.step_size;
+	int total = nand->ecc.ctx.total;
+	int eccbytes = engine_conf->code_size;
+	int eccsteps = engine_conf->nsteps;
+	u8 *ecccalc = engine_conf->calc_buf;
+	u8 *ecccode = engine_conf->code_buf;
+	unsigned int max_bitflips = 0;
+	u8 *data = req->databuf.in;
+	int i, ret;
+
+	/* Nothing to do for a raw operation */
+	if (req->mode == MTD_OPS_RAW)
+		return 0;
+
+	/* This engine does not provide BBM/free OOB bytes protection */
+	if (!req->datalen)
+		return 0;
+
+	/* No more preparation for page write */
+	if (req->type == NAND_PAGE_WRITE) {
+		nand_ecc_restore_req(&engine_conf->req_ctx, req);
+		return 0;
+	}
+
+	/* Finish a page read: retrieve the (raw) ECC bytes*/
+	ret = mtd_ooblayout_get_eccbytes(mtd, ecccode, req->oobbuf.in, 0,
+					 total);
+	if (ret)
+		return ret;
+
+	/* Calculate the ECC bytes */
+	for (i = 0; eccsteps; eccsteps--, i += eccbytes, data += eccsize)
+		nand_ecc_sw_bch_calculate(nand, data, &ecccalc[i]);
+
+	/* Finish a page read: compare and correct */
+	for (eccsteps = engine_conf->nsteps, i = 0, data = req->databuf.in;
+	     eccsteps;
+	     eccsteps--, i += eccbytes, data += eccsize) {
+		int stat =  nand_ecc_sw_bch_correct(nand, data,
+						    &ecccode[i],
+						    &ecccalc[i]);
+		if (stat < 0) {
+			mtd->ecc_stats.failed++;
+		} else {
+			mtd->ecc_stats.corrected += stat;
+			max_bitflips = max_t(unsigned int, max_bitflips, stat);
+		}
+	}
+
+	nand_ecc_restore_req(&engine_conf->req_ctx, req);
+
+	return max_bitflips;
+}
+
+static struct nand_ecc_engine_ops nand_ecc_sw_bch_engine_ops = {
+	.init_ctx = nand_ecc_sw_bch_init_ctx,
+	.cleanup_ctx = nand_ecc_sw_bch_cleanup_ctx,
+	.prepare_io_req = nand_ecc_sw_bch_prepare_io_req,
+	.finish_io_req = nand_ecc_sw_bch_finish_io_req,
+};
+
+static struct nand_ecc_engine nand_ecc_sw_bch_engine = {
+	.ops = &nand_ecc_sw_bch_engine_ops,
+};
+
+struct nand_ecc_engine *nand_ecc_sw_bch_get_engine(void)
+{
+	return &nand_ecc_sw_bch_engine;
+}
+EXPORT_SYMBOL(nand_ecc_sw_bch_get_engine);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Ivan Djelic <ivan.djelic@parrot.com>");
+MODULE_DESCRIPTION("NAND software BCH ECC support");