gpio: Add GPIO support for the Diamond Systems GPIO-MM

diff --git a/MAINTAINERS b/MAINTAINERS
index 25f4320..9481407 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -3757,6 +3757,12 @@  F:	include/linux/regulator/da9211.h
 F:	include/sound/da[79]*.h
 F:	sound/soc/codecs/da[79]*.[ch]
 
+DIAMOND SYSTEMS GPIO-MM GPIO DRIVER
+M:	William Breathitt Gray <vilhelm.gray@gmail.com>
+L:	linux-gpio@vger.kernel.org
+S:	Maintained
+F:	drivers/gpio/gpio-gpio-mm.c
+
 DIGI NEO AND CLASSIC PCI PRODUCTS
 M:	Lidza Louina <lidza.louina@gmail.com>
 M:	Mark Hounschell <markh@compro.net>
diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 6de9062..c481364 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -552,6 +552,19 @@  config GPIO_F7188X
 	  To compile this driver as a module, choose M here: the module will
 	  be called f7188x-gpio.
 
+config GPIO_GPIO_MM
+	tristate "Diamond Systems GPIO-MM GPIO support"
+	depends on ISA_BUS_API
+	help
+	  Enables GPIO support for the Diamond Systems GPIO-MM and GPIO-MM-12.
+
+	  The Diamond Systems GPIO-MM device features 48 lines of digital I/O
+	  via the emulation of dual 82C55A PPI chips. This driver provides GPIO
+	  support for these 48 channels of digital I/O.
+
+	  The base port addresses for the devices may be configured via the base
+	  array module parameter.
+
 config GPIO_IT87
 	tristate "IT87xx GPIO support"
 	help
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index 2a035ed..d0cd144 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -44,6 +44,7 @@  obj-$(CONFIG_GPIO_EP93XX)	+= gpio-ep93xx.o
 obj-$(CONFIG_GPIO_ETRAXFS)	+= gpio-etraxfs.o
 obj-$(CONFIG_GPIO_F7188X)	+= gpio-f7188x.o
 obj-$(CONFIG_GPIO_GE_FPGA)	+= gpio-ge.o
+obj-$(CONFIG_GPIO_GPIO_MM)	+= gpio-gpio-mm.o
 obj-$(CONFIG_GPIO_GRGPIO)	+= gpio-grgpio.o
 obj-$(CONFIG_GPIO_ICH)		+= gpio-ich.o
 obj-$(CONFIG_GPIO_IOP)		+= gpio-iop.o
diff --git a/drivers/gpio/gpio-gpio-mm.c b/drivers/gpio/gpio-gpio-mm.c
new file mode 100644
index 0000000..1e7def9
--- /dev/null
+++ b/drivers/gpio/gpio-gpio-mm.c
@@ -0,0 +1,267 @@ 
+/*
+ * GPIO driver for the Diamond Systems GPIO-MM
+ * Copyright (C) 2016 William Breathitt Gray
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License, version 2, as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * This driver supports the following Diamond Systems devices: GPIO-MM and
+ * GPIO-MM-12.
+ */
+#include <linux/bitops.h>
+#include <linux/device.h>
+#include <linux/errno.h>
+#include <linux/gpio/driver.h>
+#include <linux/io.h>
+#include <linux/ioport.h>
+#include <linux/isa.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/spinlock.h>
+
+#define GPIOMM_EXTENT 8
+#define MAX_NUM_GPIOMM max_num_isa_dev(GPIOMM_EXTENT)
+
+static unsigned int base[MAX_NUM_GPIOMM];
+static unsigned int num_gpiomm;
+module_param_array(base, uint, &num_gpiomm, 0);
+MODULE_PARM_DESC(base, "Diamond Systems GPIO-MM base addresses");
+
+/**
+ * struct gpiomm_gpio - GPIO device private data structure
+ * @chip:	instance of the gpio_chip
+ * @io_state:	bit I/O state (whether bit is set to input or output)
+ * @out_state:	output bits state
+ * @control:	Control registers state
+ * @lock:	synchronization lock to prevent I/O race conditions
+ * @base:	base port address of the GPIO device
+ */
+struct gpiomm_gpio {
+	struct gpio_chip chip;
+	unsigned char io_state[6];
+	unsigned char out_state[6];
+	unsigned char control[2];
+	spinlock_t lock;
+	unsigned int base;
+};
+
+static int gpiomm_gpio_get_direction(struct gpio_chip *chip,
+	unsigned int offset)
+{
+	struct gpiomm_gpio *const gpiommgpio = gpiochip_get_data(chip);
+	const unsigned int port = offset / 8;
+	const unsigned int mask = BIT(offset % 8);
+
+	return !!(gpiommgpio->io_state[port] & mask);
+}
+
+static int gpiomm_gpio_direction_input(struct gpio_chip *chip,
+	unsigned int offset)
+{
+	struct gpiomm_gpio *const gpiommgpio = gpiochip_get_data(chip);
+	const unsigned int io_port = offset / 8;
+	const unsigned int control_port = io_port / 3;
+	const unsigned int control_addr = gpiommgpio->base + 3 + control_port*4;
+	unsigned long flags;
+	unsigned int control;
+
+	spin_lock_irqsave(&gpiommgpio->lock, flags);
+
+	/* Check if configuring Port C */
+	if (io_port == 2 || io_port == 5) {
+		/* Port C can be configured by nibble */
+		if (offset % 8 > 3) {
+			gpiommgpio->io_state[io_port] |= 0xF0;
+			gpiommgpio->control[control_port] |= BIT(3);
+		} else {
+			gpiommgpio->io_state[io_port] |= 0x0F;
+			gpiommgpio->control[control_port] |= BIT(0);
+		}
+	} else {
+		gpiommgpio->io_state[io_port] |= 0xFF;
+		if (io_port == 0 || io_port == 3)
+			gpiommgpio->control[control_port] |= BIT(4);
+		else
+			gpiommgpio->control[control_port] |= BIT(1);
+	}
+
+	control = BIT(7) | gpiommgpio->control[control_port];
+	outb(control, control_addr);
+
+	spin_unlock_irqrestore(&gpiommgpio->lock, flags);
+
+	return 0;
+}
+
+static int gpiomm_gpio_direction_output(struct gpio_chip *chip,
+	unsigned int offset, int value)
+{
+	struct gpiomm_gpio *const gpiommgpio = gpiochip_get_data(chip);
+	const unsigned int io_port = offset / 8;
+	const unsigned int control_port = io_port / 3;
+	const unsigned int mask = BIT(offset % 8);
+	const unsigned int control_addr = gpiommgpio->base + 3 + control_port*4;
+	const unsigned int out_port = (io_port > 2) ? io_port + 1 : io_port;
+	unsigned long flags;
+	unsigned int control;
+
+	spin_lock_irqsave(&gpiommgpio->lock, flags);
+
+	/* Check if configuring Port C */
+	if (io_port == 2 || io_port == 5) {
+		/* Port C can be configured by nibble */
+		if (offset % 8 > 3) {
+			gpiommgpio->io_state[io_port] &= 0x0F;
+			gpiommgpio->control[control_port] &= ~BIT(3);
+		} else {
+			gpiommgpio->io_state[io_port] &= 0xF0;
+			gpiommgpio->control[control_port] &= ~BIT(0);
+		}
+	} else {
+		gpiommgpio->io_state[io_port] &= 0x00;
+		if (io_port == 0 || io_port == 3)
+			gpiommgpio->control[control_port] &= ~BIT(4);
+		else
+			gpiommgpio->control[control_port] &= ~BIT(1);
+	}
+
+	if (value)
+		gpiommgpio->out_state[io_port] |= mask;
+	else
+		gpiommgpio->out_state[io_port] &= ~mask;
+
+	control = BIT(7) | gpiommgpio->control[control_port];
+	outb(control, control_addr);
+
+	outb(gpiommgpio->out_state[io_port], gpiommgpio->base + out_port);
+
+	spin_unlock_irqrestore(&gpiommgpio->lock, flags);
+
+	return 0;
+}
+
+static int gpiomm_gpio_get(struct gpio_chip *chip, unsigned int offset)
+{
+	struct gpiomm_gpio *const gpiommgpio = gpiochip_get_data(chip);
+	const unsigned int port = offset / 8;
+	const unsigned int mask = BIT(offset % 8);
+	const unsigned int in_port = (port > 2) ? port + 1 : port;
+	unsigned long flags;
+	unsigned int port_state;
+
+	spin_lock_irqsave(&gpiommgpio->lock, flags);
+
+	/* ensure that GPIO is set for input */
+	if (!(gpiommgpio->io_state[port] & mask)) {
+		spin_unlock_irqrestore(&gpiommgpio->lock, flags);
+		return -EINVAL;
+	}
+
+	port_state = inb(gpiommgpio->base + in_port);
+
+	spin_unlock_irqrestore(&gpiommgpio->lock, flags);
+
+	return !!(port_state & mask);
+}
+
+static void gpiomm_gpio_set(struct gpio_chip *chip, unsigned int offset,
+	int value)
+{
+	struct gpiomm_gpio *const gpiommgpio = gpiochip_get_data(chip);
+	const unsigned int port = offset / 8;
+	const unsigned int mask = BIT(offset % 8);
+	const unsigned int out_port = (port > 2) ? port + 1 : port;
+	unsigned long flags;
+
+	spin_lock_irqsave(&gpiommgpio->lock, flags);
+
+	if (value)
+		gpiommgpio->out_state[port] |= mask;
+	else
+		gpiommgpio->out_state[port] &= ~mask;
+
+	outb(gpiommgpio->out_state[port], gpiommgpio->base + out_port);
+
+	spin_unlock_irqrestore(&gpiommgpio->lock, flags);
+}
+
+static int gpiomm_probe(struct device *dev, unsigned int id)
+{
+	struct gpiomm_gpio *gpiommgpio;
+	const char *const name = dev_name(dev);
+	int err;
+
+	gpiommgpio = devm_kzalloc(dev, sizeof(*gpiommgpio), GFP_KERNEL);
+	if (!gpiommgpio)
+		return -ENOMEM;
+
+	if (!devm_request_region(dev, base[id], GPIOMM_EXTENT, name)) {
+		dev_err(dev, "Unable to lock port addresses (0x%X-0x%X)\n",
+			base[id], base[id] + GPIOMM_EXTENT);
+		return -EBUSY;
+	}
+
+	gpiommgpio->chip.label = name;
+	gpiommgpio->chip.parent = dev;
+	gpiommgpio->chip.owner = THIS_MODULE;
+	gpiommgpio->chip.base = -1;
+	gpiommgpio->chip.ngpio = 48;
+	gpiommgpio->chip.get_direction = gpiomm_gpio_get_direction;
+	gpiommgpio->chip.direction_input = gpiomm_gpio_direction_input;
+	gpiommgpio->chip.direction_output = gpiomm_gpio_direction_output;
+	gpiommgpio->chip.get = gpiomm_gpio_get;
+	gpiommgpio->chip.set = gpiomm_gpio_set;
+	gpiommgpio->base = base[id];
+
+	spin_lock_init(&gpiommgpio->lock);
+
+	dev_set_drvdata(dev, gpiommgpio);
+
+	err = gpiochip_add_data(&gpiommgpio->chip, gpiommgpio);
+	if (err) {
+		dev_err(dev, "GPIO registering failed (%d)\n", err);
+		return err;
+	}
+
+	/* initialize all GPIO as output */
+	outb(0x80, base[id] + 3);
+	outb(0x00, base[id]);
+	outb(0x00, base[id] + 1);
+	outb(0x00, base[id] + 2);
+	outb(0x80, base[id] + 7);
+	outb(0x00, base[id] + 4);
+	outb(0x00, base[id] + 5);
+	outb(0x00, base[id] + 6);
+
+	return 0;
+}
+
+static int gpiomm_remove(struct device *dev, unsigned int id)
+{
+	struct gpiomm_gpio *const gpiommgpio = dev_get_drvdata(dev);
+
+	gpiochip_remove(&gpiommgpio->chip);
+
+	return 0;
+}
+
+static struct isa_driver gpiomm_driver = {
+	.probe = gpiomm_probe,
+	.driver = {
+		.name = "gpio-mm"
+	},
+	.remove = gpiomm_remove
+};
+
+module_isa_driver(gpiomm_driver, num_gpiomm);
+
+MODULE_AUTHOR("William Breathitt Gray <vilhelm.gray@gmail.com>");
+MODULE_DESCRIPTION("Diamond Systems GPIO-MM GPIO driver");
+MODULE_LICENSE("GPL v2");