mtd: nand: Introduce the ECC engine framework

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>
Link: https://lore.kernel.org/linux-mtd/20200827085208.16276-9-miquel.raynal@bootlin.com

1 files changed, 114 insertions, 0 deletions

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
@@ -184,6 +229,75 @@ struct nand_ops {
 };
 
 /**
+ * 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
  * @memorg: memory layout