drivers/gpio: Altera soft IP GPIO driver

Adds a new driver for Altera soft GPIO IP. The driver is able to do
read/write and allows GPIO to be a interrupt controller.

Tested on Altera GHRD on interrupt handling and IO.

v10:
- Updated conflicting device tree parameters
- Removed unused headers
- Used macro instead of magic numbers for ngpio
- Code readability cleanup using ?: and temporal variables
- Removed leftover garbage and unnecessary function calls
- Checked bgpio_init but unusable because Altera GPIO may not
  be a multiple of 8 bits

v9:
- Removed duplicated initialization on set_type using temporals
  to improve code readability in calling generic_handle_irq
- Using ?: ternary to reduce code size

v8:
- Using for_each_set_bit
- Added const for struct definition
- Removed naggy pr_err
- Sort alpha header
- Remove unused macros
- Use fixed width data types instead of unsigned long
- Whitespace issue fixes
- Removed _relaxed function for better compatibility across different
  CPU
- Changed irq_create_mapping to platform_get_irq updated implementation
  to use gpiochip_irqchip_add
- Reserve interrupt-cells number 2 in device tree binding for future
  use
- Remove confusing sections on devicetree bindings
- Added tristate Kconfig help text

v7:
- Used dev_warn instead of pr_warn
- Clean up unnecesarry if else indentation

v6:
- Added irq_startup and irq_shutdown
- Changed bitwise clamping style
- Cleanup bitwise operation to improve readability change naming of
  mapped irqs from virq to mapped_irq

v5:
- Dispose irq_domain mapping correctly
- Update optional binding description in binding docs

v4:
- Added vendor prefix to devicetree binding for IP specific properties
  using MMIO GPIO helper library instead of manually map PIO to memory
- altera_gpio_chip inline struct documentation to kerneldoc
- Using dev_ print to print a better failure message

v2, v3:
- Do not reference NO_IRQ
- Updated irq_set_type to only allow the hardware configured irq type
Signed-off-by: Tien Hock Loh <thloh@altera.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

MAINTAINERS

@@ -569,6 +569,12 @@ L:	nios2-dev@lists.rocketboards.org (moderated for non-subscribers)
 S:	Maintained
 F:	drivers/mailbox/mailbox-altera.c
 
+ALTERA PIO DRIVER
+M:	Tien Hock Loh <thloh@altera.com>
+L:	linux-gpio@vger.kernel.org
+S:	Maintained
+F:	drivers/gpio/gpio-altera.c
+
 ALTERA TRIPLE SPEED ETHERNET DRIVER
 M:	Vince Bridgers <vbridger@opensource.altera.com>
 L:	netdev@vger.kernel.org

drivers/gpio/Kconfig

@@ -156,6 +156,16 @@ config GPIO_DWAPB
 	  Say Y or M here to build support for the Synopsys DesignWare APB
 	  GPIO block.
 
+config GPIO_ALTERA
+	tristate "Altera GPIO"
+	depends on OF_GPIO
+	select GPIO_GENERIC
+	select GPIOLIB_IRQCHIP
+	help
+	  Say Y or M here to build support for the Altera PIO device.
+
+	  If driver is built as a module it will be called gpio-altera.
+
 config GPIO_IT8761E
 	tristate "IT8761E GPIO support"
 	depends on X86  # unconditional access to IO space.

drivers/gpio/Makefile

@@ -17,6 +17,7 @@ obj-$(CONFIG_GPIO_74XX_MMIO)	+= gpio-74xx-mmio.o
 obj-$(CONFIG_GPIO_ADNP)		+= gpio-adnp.o
 obj-$(CONFIG_GPIO_ADP5520)	+= gpio-adp5520.o
 obj-$(CONFIG_GPIO_ADP5588)	+= gpio-adp5588.o
+obj-$(CONFIG_GPIO_ALTERA)  	+= gpio-altera.o
 obj-$(CONFIG_GPIO_AMD8111)	+= gpio-amd8111.o
 obj-$(CONFIG_GPIO_ARIZONA)	+= gpio-arizona.o
 obj-$(CONFIG_GPIO_BCM_KONA)	+= gpio-bcm-kona.o