gpio: Add Avionic Design N-bit GPIO expander support

This commit adds a driver for the Avionic Design N-bit GPIO expander.
The expander provides a variable number of GPIO pins with interrupt
support.

Changes in v2:
- allow building the driver as a module
- assign of_node unconditionally
- use linear mapping IRQ domain
- properly cleanup IRQ domain
- add OF device table and annotate device tables
- emulate rising and falling edge triggers
- increase #gpio-cells to 2
- drop support for !OF
- use IS_ENABLED to conditionalize DEBUG_FS code

Changes in v3:
- make IRQ support runtime configurable (interrupt-controller property)
- drop interrupt-controller and #interrupt-cells from DT binding
- add inline to_adnp() function to wrap container_of() macro
- consistently use adnp as name for struct adnp variables
- remove irq_mask_cur and rename irq_mask to irq_enable
- fix a subtle deadlock in adnp_gpio_direction_output()
- remove dynamic allocations from debugfs code
- rename regs to num_regs to avoid confusion
- annotate non-trivial code with comments
- don't acquire mutex in adnp_gpio_get()
- assume NO_IRQ == 0

Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: devicetree-discuss@lists.ozlabs.org
Cc: Linus Walleij <linus.walleij@stericsson.com>
Cc: linux-kernel@vger.kernel.org
Acked-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Thierry Reding <thierry.reding@avionic-design.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

1 files changed, 30 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/gpio/gpio-adnp.txt b/Documentation/devicetree/bindings/gpio/gpio-adnp.txt
new file mode 100644
index 000000000000..5a09a216fe65
--- /dev/null
+++ b/Documentation/devicetree/bindings/gpio/gpio-adnp.txt
@@ -0,0 +1,30 @@
+Avionic Design N-bit GPIO expander bindings
+
+Required properties:
+- compatible: should be "ad,gpio-adnp"
+- reg: The I2C slave address for this device.
+- interrupt-parent: phandle of the parent interrupt controller.
+- interrupts: Interrupt specifier for the controllers interrupt.
+- #gpio-cells: Should be 2. The first cell is the GPIO number and the
+  second cell is used to specify optional parameters:
+  - bit 0: polarity (0: normal, 1: inverted)
+- gpio-controller: Marks the device as a GPIO controller
+- nr-gpios: The number of pins supported by the controller.
+
+Example:
+
+        gpioext: gpio-controller@41 {
+                compatible = "ad,gpio-adnp";
+                reg = <0x41>;
+
+                interrupt-parent = <&gpio>;
+                interrupts = <160 1>;
+
+                gpio-controller;
+                #gpio-cells = <2>;
+
+                interrupt-controller;
+                #interrupt-cells = <2>;
+
+                nr-gpios = <64>;
+        };