spi: Add FSI-attached SPI controller driver

There exists a set of SPI controllers on some POWER processors that may
be accessed through the FSI bus. Add a driver to traverse the FSI CFAM
engine that can access and drive the SPI controllers. This driver would
typically be used by a baseboard management controller (BMC).

The SPI controllers operate by means of programming a sequencing engine
which automatically manages the usual SPI protocol buses. The driver
programs each transfer into the sequencer as various operations
specifying the slave chip and shifting data in and out on the lines.
Signed-off-by: Eddie James <eajames@linux.ibm.com>
Link: https://lore.kernel.org/r/20200306194118.18581-3-eajames@linux.ibm.comSigned-off-by: Mark Brown <broonie@kernel.org>

MAINTAINERS

@@ -6861,6 +6861,13 @@ S:	Maintained
 F:	drivers/i2c/busses/i2c-fsi.c
 F:	Documentation/devicetree/bindings/i2c/i2c-fsi.txt
 
+FSI-ATTACHED SPI DRIVER
+M:	Eddie James <eajames@linux.ibm.com>
+L:	linux-spi@vger.kernel.org
+S:	Maintained
+F:	drivers/spi/spi-fsi.c
+F:	Documentation/devicetree/bindings/fsi/ibm,fsi2spi.yaml
+
 FSNOTIFY: FILESYSTEM NOTIFICATION INFRASTRUCTURE
 M:	Jan Kara <jack@suse.cz>
 R:	Amir Goldstein <amir73il@gmail.com>

drivers/spi/Kconfig

@@ -271,6 +271,13 @@ config SPI_FALCON
 	  has only been tested with m25p80 type chips. The hardware has no
 	  support for other types of SPI peripherals.
 
+config SPI_FSI
+	tristate "FSI SPI driver"
+	depends on FSI
+	help
+	  This enables support for the driver for FSI bus attached SPI
+	  controllers.
+
 config SPI_FSL_LPSPI
 	tristate "Freescale i.MX LPSPI controller"
 	depends on ARCH_MXC || COMPILE_TEST

drivers/spi/Makefile

@@ -42,6 +42,7 @@ spi-dw-midpci-objs			:= spi-dw-pci.o spi-dw-mid.o
 obj-$(CONFIG_SPI_EFM32)			+= spi-efm32.o
 obj-$(CONFIG_SPI_EP93XX)		+= spi-ep93xx.o
 obj-$(CONFIG_SPI_FALCON)		+= spi-falcon.o
+obj-$(CONFIG_SPI_FSI)			+= spi-fsi.o
 obj-$(CONFIG_SPI_FSL_CPM)		+= spi-fsl-cpm.o
 obj-$(CONFIG_SPI_FSL_DSPI)		+= spi-fsl-dspi.o
 obj-$(CONFIG_SPI_FSL_LIB)		+= spi-fsl-lib.o