mtd: nand: ecc-bch: Use the public nsteps field

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

mtd: nand: ecc-bch: Create the software BCH engine

Let's continue introducing the generic ECC engine abstraction in the
NAND subsystem by instantiating a first ECC engine: the software
BCH one.

While at it, make a very tidy ecc_sw_bch_init() function and move all
the sanity checks and user input management in
nand_ecc_sw_bch_init_ctx(). This second helper will be called from the
raw RAND core.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20200929230124.31491-10-miquel.raynal@bootlin.com

mtd: nand: ecc-bch: Stop using raw NAND structures

This code is meant to be reused by the SPI-NAND core. Now that the
driver has been cleaned and reorganized, use a generic ECC engine
object to store the driver's data instead of accessing members of the
nand_chip structure.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20200929230124.31491-9-miquel.raynal@bootlin.com

mtd: nand: ecc-bch: Update the prototypes to be more generic

These functions must be usable by the main NAND core, so their names
must be technology-agnostic as well as the parameters. Hence, we pass
a generic nand_device instead of a raw nand_chip structure.

As it seems that changing the raw NAND functions to always pass a
generic NAND device is a lost of time, we prefer to create dedicated
raw NAND wrappers that will be useful in the near future to do the
translation.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20200929230124.31491-8-miquel.raynal@bootlin.com

mtd: nand: ecc-bch: Drop mtd_nand_has_bch()

Like for any other compilation option, use the IS_ENABLED() macro
instead of hardcoding it.

By droping this helper we can get rid of the BCH header in nandsim.c.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20200929230124.31491-7-miquel.raynal@bootlin.com

mtd: nand: ecc-bch: Return only valid error codes

When a function is not available, returning -ENOTSUPP makes much more
sense than returning -1.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20200929230124.31491-6-miquel.raynal@bootlin.com

mtd: nand: ecc-bch: Stop exporting the private structure

The NAND BCH control structure has nothing to do outside of this
driver, all users of the nand_bch_init/free() functions just save it
to chip->ecc.priv so do it in this driver directly and return a
regular error code instead.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20200929230124.31491-5-miquel.raynal@bootlin.com

mtd: nand: ecc-bch: Move BCH code to the generic NAND layer

BCH ECC code might be later re-used by the SPI NAND layer.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20200929230124.31491-3-miquel.raynal@bootlin.com