mtd: spi-nor: Add Freescale QuadSPI driver

(0) What is the QuadSPI controller?

    The QuadSPI(Quad Serial Peripheral Interface) acts as an interface to
    one single or two external serial flash devices, each with up to 4
    bidirectional data lines.

(1) The QuadSPI controller is driven by the LUT(Look-up Table) registers.
    The LUT registers are a look-up-table for sequences of instructions.
    A valid sequence consists of four LUT registers.

(2) The definition of the LUT register shows below:

    ---------------------------------------------------
    | INSTR1 | PAD1 | OPRND1 | INSTR0 | PAD0 | OPRND0 |
    ---------------------------------------------------

    There are several types of INSTRx, such as:
	CMD	: the SPI NOR command.
	ADDR	: the address for the SPI NOR command.
	DUMMY	: the dummy cycles needed by the SPI NOR command.
	....

    There are several types of PADx, such as:
	PAD1	: use a singe I/O line.
	PAD2	: use two I/O lines.
	PAD4	: use quad I/O lines.
	....

(3) Test this driver with the JFFS2 and UBIFS:

    For jffs2:
    -------------
	#flash_eraseall /dev/mtd0
	#mount -t jffs2 /dev/mtdblock0 tmp
	#bonnie++ -d tmp -u 0 -s 10 -r 5

    For ubifs:
    -------------
	#flash_eraseall /dev/mtd0
	#ubiattach /dev/ubi_ctrl -m 0
	#ubimkvol /dev/ubi0 -N test -m
	#mount -t ubifs ubi0:test tmp
	#bonnie++ -d tmp -u 0 -s 10 -r 5
Signed-off-by: Huang Shijie <b32955@freescale.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

drivers/mtd/spi-nor/Kconfig

@@ -4,3 +4,9 @@ config MTD_SPI_NOR_BASE
 	help
 	  This is the framework for the SPI NOR which can be used by the SPI
 	  device drivers and the SPI-NOR device driver.
+config SPI_FSL_QUADSPI
+	tristate "Freescale Quad SPI controller"
+	depends on ARCH_MXC && MTD_SPI_NOR_BASE
+	help
+	  This enables support for the Quad SPI controller in master mode.
+	  We only connect the NOR to this controller now.

drivers/mtd/spi-nor/Makefile

 obj-$(CONFIG_MTD_SPI_NOR_BASE)	+= spi-nor.o
+obj-$(CONFIG_SPI_FSL_QUADSPI)	+= fsl-quadspi.o