spi: spi-mem: Add driver for NXP FlexSPI controller

- Add driver for NXP FlexSPI host controller

(0) What is the FlexSPI controller?
 FlexSPI is a flexsible SPI host controller which supports two SPI
 channels and up to 4 external devices. Each channel supports
 Single/Dual/Quad/Octal mode data transfer (1/2/4/8 bidirectional
 data lines) i.e. FlexSPI acts as an interface to external devices,
 maximum 4, each with up to 8 bidirectional data lines.

 It uses new SPI memory interface of the SPI framework to issue
 flash memory operations to up to four connected flash
 devices (2 buses with 2 CS each).

(1) Tested this driver with the mtd_debug and JFFS2 filesystem utility
 on NXP LX2160ARDB and LX2160AQDS targets.
 LX2160ARDB is having two NOR slave device connected on single bus A
 i.e. A0 and A1 (CS0 and CS1).
 LX2160AQDS is having two NOR slave device connected on separate buses
 one flash on A0 and second on B1 i.e. (CS0 and CS3).
 Verified this driver on following SPI NOR flashes:
    Micron, mt35xu512ab, [Read - 1 bit mode]
    Cypress, s25fl512s, [Read - 1/2/4 bit mode]
Signed-off-by: NYogesh Narayan Gaur <yogeshnarayan.gaur@nxp.com>
Reviewed-by: NFrieder Schrempf <frieder.schrempf@kontron.de>
Reviewed-by: NBoris Brezillon <bbrezillon@kernel.org>
Tested-by: NAshish Kumar <Ashish.Kumar@nxp.com>
Signed-off-by: NMark Brown <broonie@kernel.org>

drivers/spi/Kconfig

@@ -279,6 +279,16 @@ config SPI_FSL_QUADSPI
 	  This controller does not support generic SPI messages. It only
 	  supports the high-level SPI memory interface.
 
+config SPI_NXP_FLEXSPI
+	tristate "NXP Flex SPI controller"
+	depends on ARCH_LAYERSCAPE || HAS_IOMEM
+	help
+	  This enables support for the Flex SPI controller in master mode.
+	  Up to four slave devices can be connected on two buses with two
+	  chipselects each.
+	  This controller does not support generic SPI messages and only
+	  supports the high-level SPI memory interface.
+
 config SPI_GPIO
 	tristate "GPIO-based bitbanging SPI Master"
 	depends on GPIOLIB || COMPILE_TEST

drivers/spi/Makefile

@@ -64,6 +64,7 @@ obj-$(CONFIG_SPI_MXIC)			+= spi-mxic.o
 obj-$(CONFIG_SPI_MXS)			+= spi-mxs.o
 obj-$(CONFIG_SPI_NPCM_PSPI)		+= spi-npcm-pspi.o
 obj-$(CONFIG_SPI_NUC900)		+= spi-nuc900.o
+obj-$(CONFIG_SPI_NXP_FLEXSPI)		+= spi-nxp-fspi.o
 obj-$(CONFIG_SPI_OC_TINY)		+= spi-oc-tiny.o
 spi-octeon-objs				:= spi-cavium.o spi-cavium-octeon.o
 obj-$(CONFIG_SPI_OCTEON)		+= spi-octeon.o