gpio: add a driver for the Synopsys DesignWare APB GPIO block

The Synopsys DesignWare block is used in some ARM devices (picoxcell)
and can be configured to provide multiple banks of GPIO pins.

v12: - Add irq_startup/shutdown
     - do irq_create_mapping() in probe, irq_find_mapping() in to_irq()
     - Adjust mappings to show support for 1 gpio per port.
     - gpio-cells = <1>
v11: - Use NULL when checking existence of 'interrupts' property
     - Bindings descriptions cleanup
v10: - in documentation nr-gpio -> nr-gpios
v9:  - cleanup in dt bindings doc
     - use of_get_child_count()
v8:  - remove socfpga.dtsi changes
     - minor cleanup in devicetree documentation
v7:  - use irq_generic_chip
     - support one irq per gpio line or one irq for many
     - s/bank/port/ and other cleanup
v6:  - (atull) squash the set of patches
     - use linear irq domain
     - build fixes. Original driver was reviewed on v3.2.
     - Fix setting irq edge type for 'rising' and 'both'.
     - Support as a loadable module.
     - Use bgpio_chip's spinlock during register access.
     - Clean up register names to match spec
     - s/bank/port/ because register names use the word 'port'
     - s/nr-gpio/nr-gpios/
     - don't get/put the of_node
     - remove signoffs/acked-by's because of changes
     - other cleanup
v5:  - handle sparse bank population correctly
v3:  - depend on rather than select IRQ_DOMAIN
     - split IRQ support into a separate patch
v2:  - use Rob Herring's irqdomain in generic irq chip patches
     - use reg property to indicate bank index
     - support irqs on both edges based on LinusW's u300 driver
Signed-off-by: Jamie Iles <jamie@jamieiles.com>
Signed-off-by: Alan Tull <atull@altera.com>
Reviewed-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

Documentation/devicetree/bindings/gpio/snps-dwapb-gpio.txt

+* Synopsys DesignWare APB GPIO controller
+
+Required properties:
+- compatible : Should contain "snps,dw-apb-gpio"
+- reg : Address and length of the register set for the device.
+- #address-cells : should be 1 (for addressing port subnodes).
+- #size-cells : should be 0 (port subnodes).
+
+The GPIO controller has a configurable number of ports, each of which are
+represented as child nodes with the following properties:
+
+Required properties:
+- compatible : "snps,dw-apb-gpio-port"
+- gpio-controller : Marks the device node as a gpio controller.
+- #gpio-cells : Should be 1.  It is the pin number.
+- reg : The integer port index of the port, a single cell.
+
+Optional properties:
+- interrupt-controller : The first port may be configured to be an interrupt
+controller.
+- #interrupt-cells : Specifies the number of cells needed to encode an
+  interrupt.  Shall be set to 2.  The first cell defines the interrupt number,
+  the second encodes the triger flags encoded as described in
+  Documentation/devicetree/bindings/interrupts.txt
+- interrupt-parent : The parent interrupt controller.
+- interrupts : The interrupt to the parent controller raised when GPIOs
+  generate the interrupts.
+- snps,nr-gpios : The number of pins in the port, a single cell.
+
+Example:
+
+gpio: gpio@20000 {
+	compatible = "snps,dw-apb-gpio";
+	reg = <0x20000 0x1000>;
+	#address-cells = <1>;
+	#size-cells = <0>;
+
+	porta: gpio-controller@0 {
+		compatible = "snps,dw-apb-gpio-port";
+		gpio-controller;
+		#gpio-cells = <1>;
+		snps,nr-gpios = <8>;
+		reg = <0>;
+		interrupt-controller;
+		#interrupt-cells = <2>;
+		interrupt-parent = <&vic1>;
+		interrupts = <0>;
+	};
+
+	portb: gpio-controller@1 {
+		compatible = "snps,dw-apb-gpio-port";
+		gpio-controller;
+		#gpio-cells = <1>;
+		snps,nr-gpios = <8>;
+		reg = <1>;
+	};
+};

drivers/gpio/Kconfig

@@ -128,6 +128,15 @@ config GPIO_GENERIC_PLATFORM
 	help
 	  Say yes here to support basic platform_device memory-mapped GPIO controllers.
 
+config GPIO_DWAPB
+	tristate "Synopsys DesignWare APB GPIO driver"
+	select GPIO_GENERIC
+	select GENERIC_IRQ_CHIP
+	depends on OF_GPIO && IRQ_DOMAIN
+	help
+	  Say Y or M here to build support for the Synopsys DesignWare APB
+	  GPIO block.
+
 config GPIO_IT8761E
 	tristate "IT8761E GPIO support"
 	depends on X86  # unconditional access to IO space.

drivers/gpio/Makefile

@@ -23,6 +23,7 @@ obj-$(CONFIG_GPIO_CS5535)	+= gpio-cs5535.o
 obj-$(CONFIG_GPIO_DA9052)	+= gpio-da9052.o
 obj-$(CONFIG_GPIO_DA9055)	+= gpio-da9055.o
 obj-$(CONFIG_GPIO_DAVINCI)	+= gpio-davinci.o
+obj-$(CONFIG_GPIO_DWAPB)	+= gpio-dwapb.o
 obj-$(CONFIG_GPIO_EM)		+= gpio-em.o
 obj-$(CONFIG_GPIO_EP93XX)	+= gpio-ep93xx.o
 obj-$(CONFIG_GPIO_F7188X)	+= gpio-f7188x.o