mtd: nand: realtek-ecc: Add Realtek external ECC engine support

The Realtek RTl93xx switch SoC series has a built in ECC controller
that can provide BCH6 or BCH12 over 512 data and 6 tag bytes. It
generates 10 (BCH6) or 20 (BCH12) bytes of parity.

This engine will most likely work in conjunction with the Realtek
spi-mem based NAND controller but can work on its own. Therefore
the initial implementation will be of type external.

Remark! The engine can support any data blocks that are multiples
of 512 bytes. For now limit it to data+oob layouts that have been
analyzed from existing devices. This way it keeps compatibility
and pre-existing vendor data can be read.

Signed-off-by: Markus Stockhausen <markus.stockhausen@gmx.de>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>

Author: plappermaul

drivers/mtd/nand/Kconfig

@@ -61,6 +61,14 @@ config MTD_NAND_ECC_MEDIATEK
 	help
 	  This enables support for the hardware ECC engine from Mediatek.
 
+config MTD_NAND_ECC_REALTEK
+        tristate "Realtek RTL93xx hardware ECC engine"
+        depends on HAS_IOMEM
+        depends on MACH_REALTEK_RTL || COMPILE_TEST
+        select MTD_NAND_ECC
+        help
+          This enables support for the hardware ECC engine from Realtek.
+
 endmenu
 
 endmenu

drivers/mtd/nand/Makefile

@@ -3,6 +3,7 @@
 nandcore-objs := core.o bbt.o
 obj-$(CONFIG_MTD_NAND_CORE) += nandcore.o
 obj-$(CONFIG_MTD_NAND_ECC_MEDIATEK) += ecc-mtk.o
+obj-$(CONFIG_MTD_NAND_ECC_REALTEK) += ecc-realtek.o
 obj-$(CONFIG_SPI_QPIC_SNAND) += qpic_common.o
 obj-$(CONFIG_MTD_NAND_QCOM) += qpic_common.o
 obj-y	+= onenand/