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>

Documentation/devicetree/bindings/gpio/gpio-adnp.txt

+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>;
+	};

drivers/gpio/Kconfig

@@ -444,6 +444,17 @@ config GPIO_ADP5588_IRQ
 	  Say yes here to enable the adp5588 to be used as an interrupt
 	  controller. It requires the driver to be built in the kernel.
 
+config GPIO_ADNP
+	tristate "Avionic Design N-bit GPIO expander"
+	depends on I2C && OF
+	help
+	  This option enables support for N GPIOs found on Avionic Design
+	  I2C GPIO expanders. The register space will be extended by powers
+	  of two, so the controller will need to accomodate for that. For
+	  example: if a controller provides 48 pins, 6 registers will be
+	  enough to represent all pins, but the driver will assume a
+	  register layout for 64 pins (8 registers).
+
 comment "PCI GPIO expanders:"
 
 config GPIO_CS5535

drivers/gpio/Makefile

@@ -10,6 +10,7 @@ obj-$(CONFIG_GPIO_GENERIC)	+= gpio-generic.o
 
 obj-$(CONFIG_GPIO_74X164)	+= gpio-74x164.o
 obj-$(CONFIG_GPIO_AB8500)	+= gpio-ab8500.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_AMD8111)	+= gpio-amd8111.o

drivers/gpio/gpio-adnp.c

+/*
+ * Copyright (C) 2011-2012 Avionic Design GmbH
+ *
+ * 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.
+ */
+
+#include <linux/gpio.h>
+#include <linux/i2c.h>
+#include <linux/interrupt.h>
+#include <linux/irqdomain.h>
+#include <linux/module.h>
+#include <linux/of_irq.h>
+#include <linux/seq_file.h>
+#include <linux/slab.h>
+
+#define GPIO_DDR(gpio) (0x00 << (gpio)->reg_shift)
+#define GPIO_PLR(gpio) (0x01 << (gpio)->reg_shift)
+#define GPIO_IER(gpio) (0x02 << (gpio)->reg_shift)
+#define GPIO_ISR(gpio) (0x03 << (gpio)->reg_shift)
+#define GPIO_PTR(gpio) (0x04 << (gpio)->reg_shift)
+
+struct adnp {
+	struct i2c_client *client;
+	struct gpio_chip gpio;
+	unsigned int reg_shift;
+
+	struct mutex i2c_lock;
+
+	struct irq_domain *domain;
+	struct mutex irq_lock;
+
+	u8 *irq_enable;
+	u8 *irq_level;
+	u8 *irq_rise;
+	u8 *irq_fall;
+	u8 *irq_high;
+	u8 *irq_low;
+};
+
+static inline struct adnp *to_adnp(struct gpio_chip *chip)
+{
+	return container_of(chip, struct adnp, gpio);
+}
+
+static int adnp_read(struct adnp *adnp, unsigned offset, uint8_t *value)
+{
+	int err;
+
+	err = i2c_smbus_read_byte_data(adnp->client, offset);
+	if (err < 0) {
+		dev_err(adnp->gpio.dev, "%s failed: %d\n",
+			"i2c_smbus_read_byte_data()", err);
+		return err;
+	}
+
+	*value = err;
+	return 0;
+}
+
+static int adnp_write(struct adnp *adnp, unsigned offset, uint8_t value)
+{
+	int err;
+
+	err = i2c_smbus_write_byte_data(adnp->client, offset, value);
+	if (err < 0) {
+		dev_err(adnp->gpio.dev, "%s failed: %d\n",
+			"i2c_smbus_write_byte_data()", err);
+		return err;
+	}
+
+	return 0;
+}
+
+static int adnp_gpio_get(struct gpio_chip *chip, unsigned offset)
+{
+	struct adnp *adnp = to_adnp(chip);
+	unsigned int reg = offset >> adnp->reg_shift;
+	unsigned int pos = offset & 7;
+	u8 value;
+	int err;
+
+	err = adnp_read(adnp, GPIO_PLR(adnp) + reg, &value);
+	if (err < 0)
+		return err;
+
+	return (value & BIT(pos)) ? 1 : 0;
+}
+
+static void __adnp_gpio_set(struct adnp *adnp, unsigned offset, int value)
+{
+	unsigned int reg = offset >> adnp->reg_shift;
+	unsigned int pos = offset & 7;
+	int err;
+	u8 val;
+
+	err = adnp_read(adnp, GPIO_PLR(adnp) + reg, &val);
+	if (err < 0)
+		return;
+
+	if (value)
+		val |= BIT(pos);
+	else
+		val &= ~BIT(pos);
+
+	adnp_write(adnp, GPIO_PLR(adnp) + reg, val);
+}
+
+static void adnp_gpio_set(struct gpio_chip *chip, unsigned offset, int value)
+{
+	struct adnp *adnp = to_adnp(chip);
+
+	mutex_lock(&adnp->i2c_lock);
+	__adnp_gpio_set(adnp, offset, value);
+	mutex_unlock(&adnp->i2c_lock);
+}
+
+static int adnp_gpio_direction_input(struct gpio_chip *chip, unsigned offset)
+{
+	struct adnp *adnp = to_adnp(chip);
+	unsigned int reg = offset >> adnp->reg_shift;
+	unsigned int pos = offset & 7;
+	u8 value;
+	int err;
+
+	mutex_lock(&adnp->i2c_lock);
+
+	err = adnp_read(adnp, GPIO_DDR(adnp) + reg, &value);
+	if (err < 0)
+		goto out;
+
+	value &= ~BIT(pos);
+
+	err = adnp_write(adnp, GPIO_DDR(adnp) + reg, value);
+	if (err < 0)
+		goto out;
+
+	err = adnp_read(adnp, GPIO_DDR(adnp) + reg, &value);
+	if (err < 0)
+		goto out;
+
+	if (err & BIT(pos))
+		err = -EACCES;
+
+	err = 0;
+
+out:
+	mutex_unlock(&adnp->i2c_lock);
+	return err;
+}
+
+static int adnp_gpio_direction_output(struct gpio_chip *chip, unsigned offset,
+				      int value)
+{
+	struct adnp *adnp = to_adnp(chip);
+	unsigned int reg = offset >> adnp->reg_shift;
+	unsigned int pos = offset & 7;
+	int err;
+	u8 val;
+
+	mutex_lock(&adnp->i2c_lock);
+
+	err = adnp_read(adnp, GPIO_DDR(adnp) + reg, &val);
+	if (err < 0)
+		goto out;
+
+	val |= BIT(pos);
+
+	err = adnp_write(adnp, GPIO_DDR(adnp) + reg, val);
+	if (err < 0)
+		goto out;
+
+	err = adnp_read(adnp, GPIO_DDR(adnp) + reg, &val);
+	if (err < 0)
+		goto out;
+
+	if (!(val & BIT(pos))) {
+		err = -EPERM;
+		goto out;
+	}
+
+	__adnp_gpio_set(adnp, offset, value);
+	err = 0;
+
+out:
+	mutex_unlock(&adnp->i2c_lock);
+	return err;
+}
+
+static void adnp_gpio_dbg_show(struct seq_file *s, struct gpio_chip *chip)
+{
+	struct adnp *adnp = to_adnp(chip);
+	unsigned int num_regs = 1 << adnp->reg_shift, i, j;
+	int err;
+
+	for (i = 0; i < num_regs; i++) {
+		u8 ddr, plr, ier, isr;
+
+		mutex_lock(&adnp->i2c_lock);
+
+		err = adnp_read(adnp, GPIO_DDR(adnp) + i, &ddr);
+		if (err < 0) {
+			mutex_unlock(&adnp->i2c_lock);
+			return;
+		}
+
+		err = adnp_read(adnp, GPIO_PLR(adnp) + i, &plr);
+		if (err < 0) {
+			mutex_unlock(&adnp->i2c_lock);
+			return;
+		}
+
+		err = adnp_read(adnp, GPIO_IER(adnp) + i, &ier);
+		if (err < 0) {
+			mutex_unlock(&adnp->i2c_lock);
+			return;
+		}
+
+		err = adnp_read(adnp, GPIO_ISR(adnp) + i, &isr);
+		if (err < 0) {
+			mutex_unlock(&adnp->i2c_lock);
+			return;
+		}
+
+		mutex_unlock(&adnp->i2c_lock);
+
+		for (j = 0; j < 8; j++) {
+			unsigned int bit = (i << adnp->reg_shift) + j;
+			const char *direction = "input ";
+			const char *level = "low ";
+			const char *interrupt = "disabled";
+			const char *pending = "";
+
+			if (ddr & BIT(j))
+				direction = "output";
+
+			if (plr & BIT(j))
+				level = "high";
+
+			if (ier & BIT(j))
+				interrupt = "enabled ";
+
+			if (isr & BIT(j))
+				pending = "pending";
+
+			seq_printf(s, "%2u: %s %s IRQ %s %s\n", bit,
+				   direction, level, interrupt, pending);
+		}
+	}
+}
+
+static int adnp_gpio_setup(struct adnp *adnp, unsigned int num_gpios)
+{
+	struct gpio_chip *chip = &adnp->gpio;
+
+	adnp->reg_shift = get_count_order(num_gpios) - 3;
+
+	chip->direction_input = adnp_gpio_direction_input;
+	chip->direction_output = adnp_gpio_direction_output;
+	chip->get = adnp_gpio_get;
+	chip->set = adnp_gpio_set;
+	chip->can_sleep = 1;
+
+	if (IS_ENABLED(CONFIG_DEBUG_FS))
+		chip->dbg_show = adnp_gpio_dbg_show;
+
+	chip->base = -1;
+	chip->ngpio = num_gpios;
+	chip->label = adnp->client->name;
+	chip->dev = &adnp->client->dev;
+	chip->of_node = chip->dev->of_node;
+	chip->owner = THIS_MODULE;
+
+	return 0;
+}
+
+static irqreturn_t adnp_irq(int irq, void *data)
+{
+	struct adnp *adnp = data;
+	unsigned int num_regs, i;
+
+	num_regs = 1 << adnp->reg_shift;
+
+	for (i = 0; i < num_regs; i++) {
+		unsigned int base = i << adnp->reg_shift, bit;
+		u8 changed, level, isr, ier;
+		unsigned long pending;
+		int err;
+
+		mutex_lock(&adnp->i2c_lock);
+
+		err = adnp_read(adnp, GPIO_PLR(adnp) + i, &level);
+		if (err < 0) {
+			mutex_unlock(&adnp->i2c_lock);
+			continue;
+		}
+
+		err = adnp_read(adnp, GPIO_ISR(adnp) + i, &isr);
+		if (err < 0) {
+			mutex_unlock(&adnp->i2c_lock);
+			continue;
+		}
+
+		err = adnp_read(adnp, GPIO_IER(adnp) + i, &ier);
+		if (err < 0) {
+			mutex_unlock(&adnp->i2c_lock);
+			continue;
+		}
+
+		mutex_unlock(&adnp->i2c_lock);
+
+		/* determine pins that changed levels */
+		changed = level ^ adnp->irq_level[i];
+
+		/* compute edge-triggered interrupts */
+		pending = changed & ((adnp->irq_fall[i] & ~level) |
+				     (adnp->irq_rise[i] & level));
+
+		/* add in level-triggered interrupts */
+		pending |= (adnp->irq_high[i] & level) |
+			   (adnp->irq_low[i] & ~level);
+
+		/* mask out non-pending and disabled interrupts */
+		pending &= isr & ier;
+
+		for_each_set_bit(bit, &pending, 8) {
+			unsigned int virq;
+			virq = irq_find_mapping(adnp->domain, base + bit);
+			handle_nested_irq(virq);
+		}
+	}
+
+	return IRQ_HANDLED;
+}
+
+static int adnp_gpio_to_irq(struct gpio_chip *chip, unsigned offset)
+{
+	struct adnp *adnp = to_adnp(chip);
+	return irq_create_mapping(adnp->domain, offset);
+}
+
+static void adnp_irq_mask(struct irq_data *data)
+{
+	struct adnp *adnp = irq_data_get_irq_chip_data(data);
+	unsigned int reg = data->hwirq >> adnp->reg_shift;
+	unsigned int pos = data->hwirq & 7;
+
+	adnp->irq_enable[reg] &= ~BIT(pos);
+}
+
+static void adnp_irq_unmask(struct irq_data *data)
+{
+	struct adnp *adnp = irq_data_get_irq_chip_data(data);
+	unsigned int reg = data->hwirq >> adnp->reg_shift;
+	unsigned int pos = data->hwirq & 7;
+
+	adnp->irq_enable[reg] |= BIT(pos);
+}
+
+static int adnp_irq_set_type(struct irq_data *data, unsigned int type)
+{
+	struct adnp *adnp = irq_data_get_irq_chip_data(data);
+	unsigned int reg = data->hwirq >> adnp->reg_shift;
+	unsigned int pos = data->hwirq & 7;
+
+	if (type & IRQ_TYPE_EDGE_RISING)
+		adnp->irq_rise[reg] |= BIT(pos);
+	else
+		adnp->irq_rise[reg] &= ~BIT(pos);
+
+	if (type & IRQ_TYPE_EDGE_FALLING)
+		adnp->irq_fall[reg] |= BIT(pos);
+	else
+		adnp->irq_fall[reg] &= ~BIT(pos);
+
+	if (type & IRQ_TYPE_LEVEL_HIGH)
+		adnp->irq_high[reg] |= BIT(pos);
+	else
+		adnp->irq_high[reg] &= ~BIT(pos);
+
+	if (type & IRQ_TYPE_LEVEL_LOW)
+		adnp->irq_low[reg] |= BIT(pos);
+	else
+		adnp->irq_low[reg] &= ~BIT(pos);
+
+	return 0;
+}
+
+static void adnp_irq_bus_lock(struct irq_data *data)
+{
+	struct adnp *adnp = irq_data_get_irq_chip_data(data);
+
+	mutex_lock(&adnp->irq_lock);
+}
+
+static void adnp_irq_bus_unlock(struct irq_data *data)
+{
+	struct adnp *adnp = irq_data_get_irq_chip_data(data);
+	unsigned int num_regs = 1 << adnp->reg_shift, i;
+
+	mutex_lock(&adnp->i2c_lock);
+
+	for (i = 0; i < num_regs; i++)
+		adnp_write(adnp, GPIO_IER(adnp) + i, adnp->irq_enable[i]);
+
+	mutex_unlock(&adnp->i2c_lock);
+	mutex_unlock(&adnp->irq_lock);
+}
+
+static struct irq_chip adnp_irq_chip = {
+	.name = "gpio-adnp",
+	.irq_mask = adnp_irq_mask,
+	.irq_unmask = adnp_irq_unmask,
+	.irq_set_type = adnp_irq_set_type,
+	.irq_bus_lock = adnp_irq_bus_lock,
+	.irq_bus_sync_unlock = adnp_irq_bus_unlock,
+};
+
+static int adnp_irq_map(struct irq_domain *domain, unsigned int irq,
+			irq_hw_number_t hwirq)
+{
+	irq_set_chip_data(irq, domain->host_data);
+	irq_set_chip(irq, &adnp_irq_chip);
+	irq_set_nested_thread(irq, true);
+
+#ifdef CONFIG_ARM
+	set_irq_flags(irq, IRQF_VALID);
+#else
+	irq_set_noprobe(irq);
+#endif
+
+	return 0;
+}
+
+static const struct irq_domain_ops adnp_irq_domain_ops = {
+	.map = adnp_irq_map,
+	.xlate = irq_domain_xlate_twocell,
+};
+
+static int adnp_irq_setup(struct adnp *adnp)
+{
+	unsigned int num_regs = 1 << adnp->reg_shift, i;
+	struct gpio_chip *chip = &adnp->gpio;
+	int err;
+
+	mutex_init(&adnp->irq_lock);
+
+	/*
+	 * Allocate memory to keep track of the current level and trigger
+	 * modes of the interrupts. To avoid multiple allocations, a single
+	 * large buffer is allocated and pointers are setup to point at the
+	 * corresponding offsets. For consistency, the layout of the buffer
+	 * is chosen to match the register layout of the hardware in that
+	 * each segment contains the corresponding bits for all interrupts.
+	 */
+	adnp->irq_enable = devm_kzalloc(chip->dev, num_regs * 6, GFP_KERNEL);
+	if (!adnp->irq_enable)
+		return -ENOMEM;
+
+	adnp->irq_level = adnp->irq_enable + (num_regs * 1);
+	adnp->irq_rise = adnp->irq_enable + (num_regs * 2);
+	adnp->irq_fall = adnp->irq_enable + (num_regs * 3);
+	adnp->irq_high = adnp->irq_enable + (num_regs * 4);
+	adnp->irq_low = adnp->irq_enable + (num_regs * 5);
+
+	for (i = 0; i < num_regs; i++) {
+		/*
+		 * Read the initial level of all pins to allow the emulation
+		 * of edge triggered interrupts.
+		 */
+		err = adnp_read(adnp, GPIO_PLR(adnp) + i, &adnp->irq_level[i]);
+		if (err < 0)
+			return err;
+
+		/* disable all interrupts */
+		err = adnp_write(adnp, GPIO_IER(adnp) + i, 0);
+		if (err < 0)
+			return err;
+
+		adnp->irq_enable[i] = 0x00;
+	}
+
+	adnp->domain = irq_domain_add_linear(chip->of_node, chip->ngpio,
+					     &adnp_irq_domain_ops, adnp);
+
+	err = request_threaded_irq(adnp->client->irq, NULL, adnp_irq,
+				   IRQF_TRIGGER_RISING | IRQF_ONESHOT,
+				   dev_name(chip->dev), adnp);
+	if (err != 0) {
+		dev_err(chip->dev, "can't request IRQ#%d: %d\n",
+			adnp->client->irq, err);
+		goto error;
+	}
+
+	chip->to_irq = adnp_gpio_to_irq;
+	return 0;
+
+error:
+	irq_domain_remove(adnp->domain);
+	return err;
+}
+
+static void adnp_irq_teardown(struct adnp *adnp)
+{
+	unsigned int irq, i;
+
+	free_irq(adnp->client->irq, adnp);
+
+	for (i = 0; i < adnp->gpio.ngpio; i++) {
+		irq = irq_find_mapping(adnp->domain, i);
+		if (irq > 0)
+			irq_dispose_mapping(irq);
+	}
+
+	irq_domain_remove(adnp->domain);
+}
+
+static __devinit int adnp_i2c_probe(struct i2c_client *client,
+				    const struct i2c_device_id *id)
+{
+	struct device_node *np = client->dev.of_node;
+	struct adnp *adnp;
+	u32 num_gpios;
+	int err;
+
+	err = of_property_read_u32(np, "nr-gpios", &num_gpios);
+	if (err < 0)
+		return err;
+
+	client->irq = irq_of_parse_and_map(np, 0);
+	if (!client->irq)
+		return -EPROBE_DEFER;
+
+	adnp = devm_kzalloc(&client->dev, sizeof(*adnp), GFP_KERNEL);
+	if (!adnp)
+		return -ENOMEM;
+
+	mutex_init(&adnp->i2c_lock);
+	adnp->client = client;
+
+	err = adnp_gpio_setup(adnp, num_gpios);
+	if (err < 0)
+		return err;
+
+	if (of_find_property(np, "interrupt-controller", NULL)) {
+		err = adnp_irq_setup(adnp);
+		if (err < 0)
+			goto teardown;
+	}
+
+	err = gpiochip_add(&adnp->gpio);
+	if (err < 0)
+		goto teardown;
+
+	i2c_set_clientdata(client, adnp);
+	return 0;
+
+teardown:
+	if (of_find_property(np, "interrupt-controller", NULL))
+		adnp_irq_teardown(adnp);
+
+	return err;
+}
+
+static __devexit int adnp_i2c_remove(struct i2c_client *client)
+{
+	struct adnp *adnp = i2c_get_clientdata(client);
+	struct device_node *np = client->dev.of_node;
+	int err;
+
+	err = gpiochip_remove(&adnp->gpio);
+	if (err < 0) {
+		dev_err(&client->dev, "%s failed: %d\n", "gpiochip_remove()",
+			err);
+		return err;
+	}
+
+	if (of_find_property(np, "interrupt-controller", NULL))
+		adnp_irq_teardown(adnp);
+
+	return 0;
+}
+
+static const struct i2c_device_id adnp_i2c_id[] __devinitconst = {
+	{ "gpio-adnp" },
+	{ },
+};
+MODULE_DEVICE_TABLE(i2c, adnp_i2c_id);
+
+static const struct of_device_id adnp_of_match[] __devinitconst = {
+	{ .compatible = "ad,gpio-adnp", },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, adnp_of_match);
+
+static struct i2c_driver adnp_i2c_driver = {
+	.driver = {
+		.name = "gpio-adnp",
+		.owner = THIS_MODULE,
+		.of_match_table = of_match_ptr(adnp_of_match),
+	},
+	.probe = adnp_i2c_probe,
+	.remove = __devexit_p(adnp_i2c_remove),
+	.id_table = adnp_i2c_id,
+};
+module_i2c_driver(adnp_i2c_driver);
+
+MODULE_DESCRIPTION("Avionic Design N-bit GPIO expander");
+MODULE_AUTHOR("Thierry Reding <thierry.reding@avionic-design.de>");
+MODULE_LICENSE("GPL");