spi: Add Freescale/Motorola Coldfire QSPI driver

Add support for the QSPI controller found some on Freescale/Motorola
Coldfire MCUs.

Full duplex, active high cs, spi modes 0-3 and word sizes 8-16 bits are
supported.  The hardware drives the MISO, MOSI and SCLK lines, but the chip
selects are managed via GPIO and must be configured by the board code.

The QSPI controller has an 80 byte buffer which allows us to transfer up to 16
words at a time.  For transfers longer than 16 words, we split the buffer in
half so we can update in one half while the controller is operating on the
other half.  Interrupt latencies then ultimately limits our sustained thru-put
to something less than half the maximum speed supported by the part.

Signed-off-by: Steven King <sfking@fdwdc.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

drivers/spi/Kconfig

@@ -100,6 +100,16 @@ config SPI_BUTTERFLY
 	  inexpensive battery powered microcontroller evaluation board.
 	  This same cable can be used to flash new firmware.
 
+config SPI_COLDFIRE_QSPI
+	tristate "Freescale Coldfire QSPI controller"
+	depends on (M520x || M523x || M5249 || M527x || M528x || M532x)
+	help
+	  This enables support for the Coldfire QSPI controller in master
+	  mode.
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called coldfire_qspi.
+
 config SPI_DAVINCI
 	tristate "SPI controller driver for DaVinci/DA8xx SoC's"
 	depends on SPI_MASTER && ARCH_DAVINCI

drivers/spi/Makefile

@@ -16,6 +16,7 @@ obj-$(CONFIG_SPI_BFIN)			+= spi_bfin5xx.o
 obj-$(CONFIG_SPI_BITBANG)		+= spi_bitbang.o
 obj-$(CONFIG_SPI_AU1550)		+= au1550_spi.o
 obj-$(CONFIG_SPI_BUTTERFLY)		+= spi_butterfly.o
+obj-$(CONFIG_SPI_COLDFIRE_QSPI)		+= coldfire_qspi.o
 obj-$(CONFIG_SPI_DAVINCI)		+= davinci_spi.o
 obj-$(CONFIG_SPI_DESIGNWARE)		+= dw_spi.o
 obj-$(CONFIG_SPI_DW_PCI)		+= dw_spi_pci.o