spi: wpcm-fiu: Add driver for Nuvoton WPCM450 Flash Interface Unit (FIU)

The Flash Interface Unit (FIU) is the SPI flash controller in the
Nuvoton WPCM450 BMC SoC. It supports four chip selects, and direct
(memory-mapped) access to 16 MiB per chip. Larger flash chips can be
accessed by software-defined SPI transfers.

The FIU in newer NPCM7xx SoCs is not compatible with the WPCM450 FIU.

Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Link: https://lore.kernel.org/r/20221124191400.287918-3-j.neuschaefer@gmx.net
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: neuschaefer

drivers/spi/Kconfig

@@ -635,6 +635,17 @@ config SPI_MTK_SNFI
 	  is implemented as a SPI-MEM controller with pipelined ECC
 	  capcability.
 
+config SPI_WPCM_FIU
+	tristate "Nuvoton WPCM450 Flash Interface Unit"
+	depends on ARCH_NPCM || COMPILE_TEST
+	select REGMAP
+	help
+	  This enables support got the Flash Interface Unit SPI controller
+	  present in the Nuvoton WPCM450 SoC.
+
+	  This driver does not support generic SPI. The implementation only
+	  supports the spi-mem interface.
+
 config SPI_NPCM_FIU
 	tristate "Nuvoton NPCM FLASH Interface Unit"
 	depends on ARCH_NPCM || COMPILE_TEST

drivers/spi/Makefile

@@ -83,6 +83,7 @@ obj-$(CONFIG_SPI_MTK_NOR)		+= spi-mtk-nor.o
 obj-$(CONFIG_SPI_MTK_SNFI)		+= spi-mtk-snfi.o
 obj-$(CONFIG_SPI_MXIC)			+= spi-mxic.o
 obj-$(CONFIG_SPI_MXS)			+= spi-mxs.o
+obj-$(CONFIG_SPI_WPCM_FIU)		+= spi-wpcm-fiu.o
 obj-$(CONFIG_SPI_NPCM_FIU)		+= spi-npcm-fiu.o
 obj-$(CONFIG_SPI_NPCM_PSPI)		+= spi-npcm-pspi.o
 obj-$(CONFIG_SPI_NXP_FLEXSPI)		+= spi-nxp-fspi.o