[PATCH v10 08/20] mtd: nand: Introduce the ECC engine framework

[Miquel Raynal <miquel.raynal@bootlin.com>]

Create a generic ECC engine framework. This is a base to instantiate ECC
engine objects.

If we really want to be generic, bindings must evolve, so here is the
new logic. The following three properties are mutually exclusive:
- The nand-no-ecc-engine boolean property is set and there is no
  ECC engine to retrieve.
- The nand-use-soft-ecc-engine boolean property is set and the core
  will force using the use of software correction.
- There is a nand-ecc-engine property pointing at a node which will
  act as ECC engine.

It the later case, the property may reference:
- The NAND chip node itself (for the on-die ECC case).
- The parent node if the NAND controller embeds an ECC engine.
- Any other node being an external ECC controller as well.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
---
 drivers/mtd/nand/Kconfig  |   8 +
 drivers/mtd/nand/Makefile |   2 +
 drivers/mtd/nand/ecc.c    | 484 ++++++++++++++++++++++++++++++++++++++
 include/linux/mtd/nand.h  | 114 +++++++++
 4 files changed, 608 insertions(+)
 create mode 100644 drivers/mtd/nand/ecc.c

diff --git a/drivers/mtd/nand/Kconfig b/drivers/mtd/nand/Kconfig
index c1a45b071165..4a9aed4f0104 100644
--- a/drivers/mtd/nand/Kconfig
+++ b/drivers/mtd/nand/Kconfig
@@ -9,4 +9,12 @@ source "drivers/mtd/nand/onenand/Kconfig"
 source "drivers/mtd/nand/raw/Kconfig"
 source "drivers/mtd/nand/spi/Kconfig"
 
+menu "ECC engine support"
+
+config MTD_NAND_ECC
+       bool
+       depends on MTD_NAND_CORE
+
+endmenu
+
 endmenu
diff --git a/drivers/mtd/nand/Makefile b/drivers/mtd/nand/Makefile
index 7ecd80c0a66e..981372953b56 100644
--- a/drivers/mtd/nand/Makefile
+++ b/drivers/mtd/nand/Makefile
@@ -6,3 +6,5 @@ obj-$(CONFIG_MTD_NAND_CORE) += nandcore.o
 obj-y	+= onenand/
 obj-y	+= raw/
 obj-y	+= spi/
+
+nandcore-$(CONFIG_MTD_NAND_ECC) += ecc.o
diff --git a/drivers/mtd/nand/ecc.c b/drivers/mtd/nand/ecc.c
new file mode 100644
index 000000000000..52de9c9775a0
--- /dev/null
+++ b/drivers/mtd/nand/ecc.c
@@ -0,0 +1,484 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Generic Error-Correcting Code (ECC) engine
+ *
+ * Copyright (C) 2019 Macronix
+ * Author:
+ *     Miquèl RAYNAL <miquel.raynal@bootlin.com>
+ *
+ *
+ * This file describes the abstraction of any NAND ECC engine. It has been
+ * designed to fit most cases, including parallel NANDs and SPI-NANDs.
+ *
+ * There are three main situations where instantiating this ECC engine makes
+ * sense:
+ *   - external: The ECC engine is outside the NAND pipeline, typically this
+ *               is a software ECC engine, or an hardware engine that is
+ *               outside the NAND controller pipeline.
+ *   - pipelined: The ECC engine is inside the NAND pipeline, ie. on the
+ *                controller's side. This is the case of most of the raw NAND
+ *                controllers. In the pipeline case, the ECC bytes are
+ *                generated/data corrected on the fly when a page is
+ *                written/read.
+ *   - ondie: The ECC engine is inside the NAND pipeline, on the chip's side.
+ *            Some NAND chips can correct themselves the data.
+ *
+ * Besides the initial setup and final cleanups, the interfaces are rather
+ * simple:
+ *   - prepare: Prepare an I/O request. Enable/disable the ECC engine based on
+ *              the I/O request type. In case of software correction or external
+ *              engine, this step may involve to derive the ECC bytes and place
+ *              them in the OOB area before a write.
+ *   - finish: Finish an I/O request. Correct the data in case of a read
+ *             request and report the number of corrected bits/uncorrectable
+ *             errors. Most likely empty for write operations, unless you have
+ *             hardware specific stuff to do, like shutting down the engine to
+ *             save power.
+ *
+ * The I/O request should be enclosed in a prepare()/finish() pair of calls
+ * and will behave differently depending on the requested I/O type:
+ *   - raw: Correction disabled
+ *   - ecc: Correction enabled
+ *
+ * The request direction is impacting the logic as well:
+ *   - read: Load data from the NAND chip
+ *   - write: Store data in the NAND chip
+ *
+ * Mixing all this combinations together gives the following behavior.
+ * Those are just examples, drivers are free to add custom steps in their
+ * prepare/finish hook.
+ *
+ * [external ECC engine]
+ *   - external + prepare + raw + read: do nothing
+ *   - external + finish  + raw + read: do nothing
+ *   - external + prepare + raw + write: do nothing
+ *   - external + finish  + raw + write: do nothing
+ *   - external + prepare + ecc + read: do nothing
+ *   - external + finish  + ecc + read: calculate expected ECC bytes, extract
+ *                                      ECC bytes from OOB buffer, correct
+ *                                      and report any bitflip/error
+ *   - external + prepare + ecc + write: calculate ECC bytes and store them at
+ *                                       the right place in the OOB buffer based
+ *                                       on the OOB layout
+ *   - external + finish  + ecc + write: do nothing
+ *
+ * [pipelined ECC engine]
+ *   - pipelined + prepare + raw + read: disable the controller's ECC engine if
+ *                                       activated
+ *   - pipelined + finish  + raw + read: do nothing
+ *   - pipelined + prepare + raw + write: disable the controller's ECC engine if
+ *                                        activated
+ *   - pipelined + finish  + raw + write: do nothing
+ *   - pipelined + prepare + ecc + read: enable the controller's ECC engine if
+ *                                       deactivated
+ *   - pipelined + finish  + ecc + read: check the status, report any
+ *                                       error/bitflip
+ *   - pipelined + prepare + ecc + write: enable the controller's ECC engine if
+ *                                        deactivated
+ *   - pipelined + finish  + ecc + write: do nothing
+ *
+ * [ondie ECC engine]
+ *   - ondie + prepare + raw + read: send commands to disable the on-chip ECC
+ *                                   engine if activated
+ *   - ondie + finish  + raw + read: do nothing
+ *   - ondie + prepare + raw + write: send commands to disable the on-chip ECC
+ *                                    engine if activated
+ *   - ondie + finish  + raw + write: do nothing
+ *   - ondie + prepare + ecc + read: send commands to enable the on-chip ECC
+ *                                   engine if deactivated
+ *   - ondie + finish  + ecc + read: send commands to check the status, report
+ *                                   any error/bitflip
+ *   - ondie + prepare + ecc + write: send commands to enable the on-chip ECC
+ *                                    engine if deactivated
+ *   - ondie + finish  + ecc + write: do nothing
+ */
+
+#include <linux/module.h>
+#include <linux/mtd/nand.h>
+
+/**
+ * nand_ecc_init_ctx - Init the ECC engine context
+ * @nand: the NAND device
+ *
+ * On success, the caller is responsible of calling @nand_ecc_cleanup_ctx().
+ */
+int nand_ecc_init_ctx(struct nand_device *nand)
+{
+	if (!nand->ecc.engine->ops->init_ctx)
+		return 0;
+
+	return nand->ecc.engine->ops->init_ctx(nand);
+}
+EXPORT_SYMBOL(nand_ecc_init_ctx);
+
+/**
+ * nand_ecc_cleanup_ctx - Cleanup the ECC engine context
+ * @nand: the NAND device
+ */
+void nand_ecc_cleanup_ctx(struct nand_device *nand)
+{
+	if (nand->ecc.engine->ops->cleanup_ctx)
+		nand->ecc.engine->ops->cleanup_ctx(nand);
+}
+EXPORT_SYMBOL(nand_ecc_cleanup_ctx);
+
+/**
+ * nand_ecc_prepare_io_req - Prepare an I/O request
+ * @nand: the NAND device
+ * @req: the I/O request
+ */
+int nand_ecc_prepare_io_req(struct nand_device *nand,
+			    struct nand_page_io_req *req)
+{
+	if (!nand->ecc.engine->ops->prepare_io_req)
+		return 0;
+
+	return nand->ecc.engine->ops->prepare_io_req(nand, req);
+}
+EXPORT_SYMBOL(nand_ecc_prepare_io_req);
+
+/**
+ * nand_ecc_finish_io_req - Finish an I/O request
+ * @nand: the NAND device
+ * @req: the I/O request
+ */
+int nand_ecc_finish_io_req(struct nand_device *nand,
+			   struct nand_page_io_req *req)
+{
+	if (!nand->ecc.engine->ops->finish_io_req)
+		return 0;
+
+	return nand->ecc.engine->ops->finish_io_req(nand, req);
+}
+EXPORT_SYMBOL(nand_ecc_finish_io_req);
+
+/* Define default OOB placement schemes for large and small page devices */
+static int nand_ooblayout_ecc_sp(struct mtd_info *mtd, int section,
+				 struct mtd_oob_region *oobregion)
+{
+	struct nand_device *nand = mtd_to_nanddev(mtd);
+	unsigned int total_ecc_bytes = nand->ecc.ctx.total;
+
+	if (section > 1)
+		return -ERANGE;
+
+	if (!section) {
+		oobregion->offset = 0;
+		if (mtd->oobsize == 16)
+			oobregion->length = 4;
+		else
+			oobregion->length = 3;
+	} else {
+		if (mtd->oobsize == 8)
+			return -ERANGE;
+
+		oobregion->offset = 6;
+		oobregion->length = total_ecc_bytes - 4;
+	}
+
+	return 0;
+}
+
+static int nand_ooblayout_free_sp(struct mtd_info *mtd, int section,
+				  struct mtd_oob_region *oobregion)
+{
+	if (section > 1)
+		return -ERANGE;
+
+	if (mtd->oobsize == 16) {
+		if (section)
+			return -ERANGE;
+
+		oobregion->length = 8;
+		oobregion->offset = 8;
+	} else {
+		oobregion->length = 2;
+		if (!section)
+			oobregion->offset = 3;
+		else
+			oobregion->offset = 6;
+	}
+
+	return 0;
+}
+
+static const struct mtd_ooblayout_ops nand_ooblayout_sp_ops = {
+	.ecc = nand_ooblayout_ecc_sp,
+	.free = nand_ooblayout_free_sp,
+};
+
+const struct mtd_ooblayout_ops *nand_get_small_page_ooblayout(void)
+{
+	return &nand_ooblayout_sp_ops;
+}
+EXPORT_SYMBOL_GPL(nand_get_small_page_ooblayout);
+
+static int nand_ooblayout_ecc_lp(struct mtd_info *mtd, int section,
+				 struct mtd_oob_region *oobregion)
+{
+	struct nand_device *nand = mtd_to_nanddev(mtd);
+	unsigned int total_ecc_bytes = nand->ecc.ctx.total;
+
+	if (section || !total_ecc_bytes)
+		return -ERANGE;
+
+	oobregion->length = total_ecc_bytes;
+	oobregion->offset = mtd->oobsize - oobregion->length;
+
+	return 0;
+}
+
+static int nand_ooblayout_free_lp(struct mtd_info *mtd, int section,
+				  struct mtd_oob_region *oobregion)
+{
+	struct nand_device *nand = mtd_to_nanddev(mtd);
+	unsigned int total_ecc_bytes = nand->ecc.ctx.total;
+
+	if (section)
+		return -ERANGE;
+
+	oobregion->length = mtd->oobsize - total_ecc_bytes - 2;
+	oobregion->offset = 2;
+
+	return 0;
+}
+
+static const struct mtd_ooblayout_ops nand_ooblayout_lp_ops = {
+	.ecc = nand_ooblayout_ecc_lp,
+	.free = nand_ooblayout_free_lp,
+};
+
+const struct mtd_ooblayout_ops *nand_get_large_page_ooblayout(void)
+{
+	return &nand_ooblayout_lp_ops;
+}
+EXPORT_SYMBOL_GPL(nand_get_large_page_ooblayout);
+
+/*
+ * Support the old "large page" layout used for 1-bit Hamming ECC where ECC
+ * are placed at a fixed offset.
+ */
+static int nand_ooblayout_ecc_lp_hamming(struct mtd_info *mtd, int section,
+					 struct mtd_oob_region *oobregion)
+{
+	struct nand_device *nand = mtd_to_nanddev(mtd);
+	unsigned int total_ecc_bytes = nand->ecc.ctx.total;
+
+	if (section)
+		return -ERANGE;
+
+	switch (mtd->oobsize) {
+	case 64:
+		oobregion->offset = 40;
+		break;
+	case 128:
+		oobregion->offset = 80;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	oobregion->length = total_ecc_bytes;
+	if (oobregion->offset + oobregion->length > mtd->oobsize)
+		return -ERANGE;
+
+	return 0;
+}
+
+static int nand_ooblayout_free_lp_hamming(struct mtd_info *mtd, int section,
+					  struct mtd_oob_region *oobregion)
+{
+	struct nand_device *nand = mtd_to_nanddev(mtd);
+	unsigned int total_ecc_bytes = nand->ecc.ctx.total;
+	int ecc_offset = 0;
+
+	if (section < 0 || section > 1)
+		return -ERANGE;
+
+	switch (mtd->oobsize) {
+	case 64:
+		ecc_offset = 40;
+		break;
+	case 128:
+		ecc_offset = 80;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	if (section == 0) {
+		oobregion->offset = 2;
+		oobregion->length = ecc_offset - 2;
+	} else {
+		oobregion->offset = ecc_offset + total_ecc_bytes;
+		oobregion->length = mtd->oobsize - oobregion->offset;
+	}
+
+	return 0;
+}
+
+static const struct mtd_ooblayout_ops nand_ooblayout_lp_hamming_ops = {
+	.ecc = nand_ooblayout_ecc_lp_hamming,
+	.free = nand_ooblayout_free_lp_hamming,
+};
+
+const struct mtd_ooblayout_ops *nand_get_large_page_hamming_ooblayout(void)
+{
+	return &nand_ooblayout_lp_hamming_ops;
+}
+EXPORT_SYMBOL_GPL(nand_get_large_page_hamming_ooblayout);
+
+static enum nand_ecc_engine_type
+of_get_nand_ecc_engine_type(struct device_node *np)
+{
+	struct device_node *eng_np;
+
+	if (of_property_read_bool(np, "nand-no-ecc-engine"))
+		return NAND_ECC_ENGINE_TYPE_NONE;
+
+	if (of_property_read_bool(np, "nand-use-soft-ecc-engine"))
+		return NAND_ECC_ENGINE_TYPE_SOFT;
+
+	eng_np = of_parse_phandle(np, "nand-ecc-engine", 0);
+	of_node_put(eng_np);
+
+	if (eng_np) {
+		if (eng_np == np)
+			return NAND_ECC_ENGINE_TYPE_ON_DIE;
+		else
+			return NAND_ECC_ENGINE_TYPE_ON_HOST;
+	}
+
+	return NAND_ECC_ENGINE_TYPE_INVALID;
+}
+
+static const char * const nand_ecc_placement[] = {
+	[NAND_ECC_PLACEMENT_OOB] = "oob",
+	[NAND_ECC_PLACEMENT_INTERLEAVED] = "interleaved",
+};
+
+enum nand_ecc_placement of_get_nand_ecc_placement(struct device_node *np)
+{
+	enum nand_ecc_placement placement;
+	const char *pm;
+	int err;
+
+	err = of_property_read_string(np, "nand-ecc-placement", &pm);
+	if (!err) {
+		for (placement = NAND_ECC_PLACEMENT_OOB;
+		     placement < ARRAY_SIZE(nand_ecc_placement); placement++) {
+			if (!strcasecmp(pm, nand_ecc_placement[placement]))
+				return placement;
+		}
+	}
+
+	return NAND_ECC_PLACEMENT_UNKNOWN;
+}
+
+static const char * const nand_ecc_algos[] = {
+	[NAND_ECC_ALGO_HAMMING] = "hamming",
+	[NAND_ECC_ALGO_BCH] = "bch",
+	[NAND_ECC_ALGO_RS] = "rs",
+};
+
+static enum nand_ecc_algo of_get_nand_ecc_algo(struct device_node *np)
+{
+	enum nand_ecc_algo ecc_algo;
+	const char *pm;
+	int err;
+
+	err = of_property_read_string(np, "nand-ecc-algo", &pm);
+	if (!err) {
+		for (ecc_algo = NAND_ECC_ALGO_HAMMING;
+		     ecc_algo < ARRAY_SIZE(nand_ecc_algos);
+		     ecc_algo++) {
+			if (!strcasecmp(pm, nand_ecc_algos[ecc_algo]))
+				return ecc_algo;
+		}
+	}
+
+	return NAND_ECC_ALGO_UNKNOWN;
+}
+
+static int of_get_nand_ecc_step_size(struct device_node *np)
+{
+	int ret;
+	u32 val;
+
+	ret = of_property_read_u32(np, "nand-ecc-step-size", &val);
+	return ret ? ret : val;
+}
+
+static int of_get_nand_ecc_strength(struct device_node *np)
+{
+	int ret;
+	u32 val;
+
+	ret = of_property_read_u32(np, "nand-ecc-strength", &val);
+	return ret ? ret : val;
+}
+
+void of_get_nand_ecc_user_config(struct nand_device *nand)
+{
+	struct device_node *dn = nanddev_get_of_node(nand);
+	int strength, size;
+
+	nand->ecc.user_conf.engine_type = of_get_nand_ecc_engine_type(dn);
+	nand->ecc.user_conf.algo = of_get_nand_ecc_algo(dn);
+	nand->ecc.user_conf.placement = of_get_nand_ecc_placement(dn);
+
+	strength = of_get_nand_ecc_strength(dn);
+	if (strength >= 0)
+		nand->ecc.user_conf.strength = strength;
+
+	size = of_get_nand_ecc_step_size(dn);
+	if (size >= 0)
+		nand->ecc.user_conf.step_size = size;
+
+	if (of_property_read_bool(dn, "nand-ecc-maximize"))
+		nand->ecc.user_conf.flags |= NAND_ECC_MAXIMIZE_STRENGTH;
+}
+EXPORT_SYMBOL(of_get_nand_ecc_user_config);
+
+/**
+ * nand_ecc_is_strong_enough - Check if the chip configuration meets the
+ *                             datasheet requirements.
+ *
+ * @nand: Device to check
+ *
+ * If our configuration corrects A bits per B bytes and the minimum
+ * required correction level is X bits per Y bytes, then we must ensure
+ * both of the following are true:
+ *
+ * (1) A / B >= X / Y
+ * (2) A >= X
+ *
+ * Requirement (1) ensures we can correct for the required bitflip density.
+ * Requirement (2) ensures we can correct even when all bitflips are clumped
+ * in the same sector.
+ */
+bool nand_ecc_is_strong_enough(struct nand_device *nand)
+{
+	const struct nand_ecc_props *reqs = nanddev_get_ecc_requirements(nand);
+	const struct nand_ecc_props *conf = nanddev_get_ecc_conf(nand);
+	struct mtd_info *mtd = nanddev_to_mtd(nand);
+	int corr, ds_corr;
+
+	if (conf->step_size == 0 || reqs->step_size == 0)
+		/* Not enough information */
+		return true;
+
+	/*
+	 * We get the number of corrected bits per page to compare
+	 * the correction density.
+	 */
+	corr = (mtd->writesize * conf->strength) / conf->step_size;
+	ds_corr = (mtd->writesize * reqs->strength) / reqs->step_size;
+
+	return corr >= ds_corr && conf->strength >= reqs->strength;
+}
+EXPORT_SYMBOL(nand_ecc_is_strong_enough);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Miquel Raynal <miquel.raynal@bootlin.com>");
+MODULE_DESCRIPTION("Generic ECC engine");
diff --git a/include/linux/mtd/nand.h b/include/linux/mtd/nand.h
index e754a6fc8a4b..8cf5bdbea782 100644
--- a/include/linux/mtd/nand.h
+++ b/include/linux/mtd/nand.h
@@ -127,6 +127,40 @@ struct nand_page_io_req {
 	int mode;
 };
 
+const struct mtd_ooblayout_ops *nand_get_small_page_ooblayout(void);
+const struct mtd_ooblayout_ops *nand_get_large_page_ooblayout(void);
+const struct mtd_ooblayout_ops *nand_get_large_page_hamming_ooblayout(void);
+
+/**
+ * enum nand_ecc_engine_type - NAND ECC engine type
+ * @NAND_ECC_ENGINE_TYPE_INVALID: Invalid value
+ * @NAND_ECC_ENGINE_TYPE_NONE: No ECC correction
+ * @NAND_ECC_ENGINE_TYPE_SOFT: Software ECC correction
+ * @NAND_ECC_ENGINE_TYPE_ON_HOST: On host hardware ECC correction
+ * @NAND_ECC_ENGINE_TYPE_ON_DIE: On chip hardware ECC correction
+ */
+enum nand_ecc_engine_type {
+	NAND_ECC_ENGINE_TYPE_INVALID,
+	NAND_ECC_ENGINE_TYPE_NONE,
+	NAND_ECC_ENGINE_TYPE_SOFT,
+	NAND_ECC_ENGINE_TYPE_ON_HOST,
+	NAND_ECC_ENGINE_TYPE_ON_DIE,
+};
+
+/**
+ * enum nand_ecc_placement - NAND ECC bytes placement
+ * @NAND_ECC_PLACEMENT_UNKNOWN: The actual position of the ECC bytes is unknown
+ * @NAND_ECC_PLACEMENT_OOB: The ECC bytes are located in the OOB area
+ * @NAND_ECC_PLACEMENT_INTERLEAVED: Syndrome layout, there are ECC bytes
+ *                                  interleaved with regular data in the main
+ *                                  area
+ */
+enum nand_ecc_placement {
+	NAND_ECC_PLACEMENT_UNKNOWN,
+	NAND_ECC_PLACEMENT_OOB,
+	NAND_ECC_PLACEMENT_INTERLEAVED,
+};
+
 /**
  * enum nand_ecc_algo - NAND ECC algorithm
  * @NAND_ECC_ALGO_UNKNOWN: Unknown algorithm
@@ -143,16 +177,27 @@ enum nand_ecc_algo {
 
 /**
  * struct nand_ecc_props - NAND ECC properties
+ * @engine_type: ECC engine type
+ * @placement: OOB placement (if relevant)
+ * @algo: ECC algorithm (if relevant)
  * @strength: ECC strength
  * @step_size: Number of bytes per step
+ * @flags: Misc properties
  */
 struct nand_ecc_props {
+	enum nand_ecc_engine_type engine_type;
+	enum nand_ecc_placement placement;
+	enum nand_ecc_algo algo;
 	unsigned int strength;
 	unsigned int step_size;
+	unsigned int flags;
 };
 
 #define NAND_ECCREQ(str, stp) { .strength = (str), .step_size = (stp) }
 
+/* NAND ECC misc flags */
+#define NAND_ECC_MAXIMIZE_STRENGTH BIT(0)
+
 /**
  * struct nand_bbt - bad block table object
  * @cache: in memory BBT cache
@@ -183,6 +228,75 @@ struct nand_ops {
 	bool (*isbad)(struct nand_device *nand, const struct nand_pos *pos);
 };
 
+/**
+ * struct nand_ecc_context - Context for the ECC engine
+ * @conf: basic ECC engine parameters
+ * @total: total number of bytes used for storing ECC codes, this is used by
+ *         generic OOB layouts
+ * @priv: ECC engine driver private data
+ */
+struct nand_ecc_context {
+	struct nand_ecc_props conf;
+	unsigned int total;
+	void *priv;
+};
+
+/**
+ * struct nand_ecc_engine_ops - ECC engine operations
+ * @init_ctx: given a desired user configuration for the pointed NAND device,
+ *            requests the ECC engine driver to setup a configuration with
+ *            values it supports.
+ * @cleanup_ctx: clean the context initialized by @init_ctx.
+ * @prepare_io_req: is called before reading/writing a page to prepare the I/O
+ *                  request to be performed with ECC correction.
+ * @finish_io_req: is called after reading/writing a page to terminate the I/O
+ *                 request and ensure proper ECC correction.
+ */
+struct nand_ecc_engine_ops {
+	int (*init_ctx)(struct nand_device *nand);
+	void (*cleanup_ctx)(struct nand_device *nand);
+	int (*prepare_io_req)(struct nand_device *nand,
+			      struct nand_page_io_req *req);
+	int (*finish_io_req)(struct nand_device *nand,
+			     struct nand_page_io_req *req);
+};
+
+/**
+ * struct nand_ecc_engine - ECC engine abstraction for NAND devices
+ * @ops: ECC engine operations
+ */
+struct nand_ecc_engine {
+	struct nand_ecc_engine_ops *ops;
+};
+
+void of_get_nand_ecc_user_config(struct nand_device *nand);
+int nand_ecc_init_ctx(struct nand_device *nand);
+void nand_ecc_cleanup_ctx(struct nand_device *nand);
+int nand_ecc_prepare_io_req(struct nand_device *nand,
+			    struct nand_page_io_req *req);
+int nand_ecc_finish_io_req(struct nand_device *nand,
+			   struct nand_page_io_req *req);
+bool nand_ecc_is_strong_enough(struct nand_device *nand);
+
+/**
+ * struct nand_ecc - Information relative to the ECC
+ * @defaults: Default values, depend on the underlying subsystem
+ * @requirements: ECC requirements from the NAND chip perspective
+ * @user_conf: User desires in terms of ECC parameters
+ * @ctx: ECC context for the ECC engine, derived from the device @requirements
+ *       the @user_conf and the @defaults
+ * @ondie_engine: On-die ECC engine reference, if any
+ * @engine: ECC engine actually bound
+ */
+struct nand_ecc {
+	struct nand_ecc_props defaults;
+	struct nand_ecc_props requirements;
+	struct nand_ecc_props user_conf;
+	struct nand_ecc_context ctx;
+	struct nand_ecc_engine *ondie_engine;
+	struct nand_ecc_engine *engine;
+};
+
 /**
  * struct nand_device - NAND device
  * @mtd: MTD instance attached to the NAND device
-- 
2.20.1