[PATCH v3 3/3] gpio: add support for the Diolan DLN-2 USB GPIO driver

[Octavian Purdila <octavian.purdila-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>]

From: Daniel Baluta <daniel.baluta-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>

This patch adds GPIO and IRQ support for the Diolan DLN-2 GPIO module.

Information about the USB protocol interface can be found in the
Programmer's Reference Manual [1], see section 2.9 for the GPIO
module commands and responses.

[1] https://www.diolan.com/downloads/dln-api-manual.pdf

Signed-off-by: Daniel Baluta <daniel.baluta-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Signed-off-by: Octavian Purdila <octavian.purdila-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
---
 drivers/gpio/Kconfig     |  12 ++
 drivers/gpio/Makefile    |   1 +
 drivers/gpio/gpio-dln2.c | 537 +++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 550 insertions(+)
 create mode 100644 drivers/gpio/gpio-dln2.c

diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 9de1515..6a9e352 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -897,4 +897,16 @@ config GPIO_VIPERBOARD
           River Tech's viperboard.h for detailed meaning
           of the module parameters.
 
+config GPIO_DLN2
+	tristate "Diolan DLN2 GPIO support"
+	depends on USB && MFD_DLN2
+	select GPIOLIB_IRQCHIP
+
+	help
+	  Select this option to enable GPIO driver for the Diolan DLN2
+	  board.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called gpio-dln2.
+
 endif
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index 5d024e3..eaa97a0 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -26,6 +26,7 @@ obj-$(CONFIG_GPIO_CRYSTAL_COVE)	+= gpio-crystalcove.o
 obj-$(CONFIG_GPIO_DA9052)	+= gpio-da9052.o
 obj-$(CONFIG_GPIO_DA9055)	+= gpio-da9055.o
 obj-$(CONFIG_GPIO_DAVINCI)	+= gpio-davinci.o
+obj-$(CONFIG_GPIO_DLN2)		+= gpio-dln2.o
 obj-$(CONFIG_GPIO_DWAPB)	+= gpio-dwapb.o
 obj-$(CONFIG_GPIO_EM)		+= gpio-em.o
 obj-$(CONFIG_GPIO_EP93XX)	+= gpio-ep93xx.o
diff --git a/drivers/gpio/gpio-dln2.c b/drivers/gpio/gpio-dln2.c
new file mode 100644
index 0000000..f8c0bcb
--- /dev/null
+++ b/drivers/gpio/gpio-dln2.c
@@ -0,0 +1,537 @@
+/*
+ * Driver for the Diolan DLN-2 USB-GPIO adapter
+ *
+ * Copyright (c) 2014 Intel Corporation
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation, version 2.
+ */
+
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+#include <linux/mutex.h>
+#include <linux/irqdomain.h>
+#include <linux/irq.h>
+#include <linux/irqchip/chained_irq.h>
+#include <linux/usb.h>
+#include <linux/gpio.h>
+#include <linux/gpio/driver.h>
+#include <linux/ptrace.h>
+#include <linux/wait.h>
+#include <linux/platform_device.h>
+#include <linux/mfd/dln2.h>
+
+#define DRIVER_NAME "dln2-gpio"
+
+#define DLN2_GPIO_ID			0x01
+
+#define DLN2_GPIO_GET_PORT_COUNT	DLN2_CMD(0x00, DLN2_GPIO_ID)
+#define DLN2_GPIO_GET_PIN_COUNT		DLN2_CMD(0x01, DLN2_GPIO_ID)
+#define DLN2_GPIO_SET_DEBOUNCE		DLN2_CMD(0x04, DLN2_GPIO_ID)
+#define DLN2_GPIO_GET_DEBOUNCE		DLN2_CMD(0x05, DLN2_GPIO_ID)
+#define DLN2_GPIO_PORT_GET_VAL		DLN2_CMD(0x06, DLN2_GPIO_ID)
+#define DLN2_GPIO_PIN_GET_VAL		DLN2_CMD(0x0B, DLN2_GPIO_ID)
+#define DLN2_GPIO_PIN_SET_OUT_VAL	DLN2_CMD(0x0C, DLN2_GPIO_ID)
+#define DLN2_GPIO_PIN_GET_OUT_VAL	DLN2_CMD(0x0D, DLN2_GPIO_ID)
+#define DLN2_GPIO_CONDITION_MET_EV	DLN2_CMD(0x0F, DLN2_GPIO_ID)
+#define DLN2_GPIO_PIN_ENABLE		DLN2_CMD(0x10, DLN2_GPIO_ID)
+#define DLN2_GPIO_PIN_DISABLE		DLN2_CMD(0x11, DLN2_GPIO_ID)
+#define DLN2_GPIO_PIN_SET_DIRECTION	DLN2_CMD(0x13, DLN2_GPIO_ID)
+#define DLN2_GPIO_PIN_GET_DIRECTION	DLN2_CMD(0x14, DLN2_GPIO_ID)
+#define DLN2_GPIO_PIN_SET_EVENT_CFG	DLN2_CMD(0x1E, DLN2_GPIO_ID)
+#define DLN2_GPIO_PIN_GET_EVENT_CFG	DLN2_CMD(0x1F, DLN2_GPIO_ID)
+
+#define DLN2_GPIO_EVENT_NONE		0
+#define DLN2_GPIO_EVENT_CHANGE		1
+#define DLN2_GPIO_EVENT_LVL_HIGH	2
+#define DLN2_GPIO_EVENT_LVL_LOW		3
+#define DLN2_GPIO_EVENT_CHANGE_RISING	0x11
+#define DLN2_GPIO_EVENT_CHANGE_FALLING  0x21
+#define DLN2_GPIO_EVENT_MASK		0x0F
+
+#define DLN2_GPIO_MAX_PINS 32
+
+struct dln2_irq_work {
+	struct work_struct work;
+	struct dln2_gpio *dln2;
+	int pin, type;
+};
+
+struct dln2_remove_work {
+	struct delayed_work work;
+	struct dln2_gpio *dln2;
+};
+
+struct dln2_gpio {
+	struct platform_device *pdev;
+	struct gpio_chip gpio;
+
+	DECLARE_BITMAP(irqs_masked, DLN2_GPIO_MAX_PINS);
+	DECLARE_BITMAP(irqs_enabled, DLN2_GPIO_MAX_PINS);
+	DECLARE_BITMAP(irqs_pending, DLN2_GPIO_MAX_PINS);
+	struct dln2_irq_work irq_work[DLN2_GPIO_MAX_PINS];
+	struct dln2_remove_work remove_work;
+};
+
+struct dln2_gpio_pin {
+	__le16 pin;
+} __packed;
+
+struct dln2_gpio_pin_val {
+	__le16 pin;
+	u8 value;
+} __packed;
+
+static int dln2_gpio_get_pin_count(struct platform_device *pdev)
+{
+	__le16 count;
+	int ret, len = sizeof(count);
+
+	ret = dln2_transfer(pdev, DLN2_GPIO_GET_PIN_COUNT, NULL, 0, &count,
+			    &len);
+	if (ret < 0)
+		return ret;
+
+	if (len < sizeof(count))
+		return -EPROTO;
+
+	return le16_to_cpu(count);
+}
+
+static int dln2_gpio_pin_cmd(struct dln2_gpio *dln2, int cmd, unsigned pin)
+{
+	struct dln2_gpio_pin req = {
+		.pin = cpu_to_le16(pin),
+	};
+
+	return dln2_transfer(dln2->pdev, cmd, &req, sizeof(req), NULL, NULL);
+}
+
+static int dln2_gpio_pin_val(struct dln2_gpio *dln2, int cmd, unsigned int pin)
+{
+	struct dln2_gpio_pin req = {
+		.pin = cpu_to_le16(pin),
+	};
+	struct dln2_gpio_pin_val rsp;
+	int ret, len = sizeof(rsp);
+
+	ret = dln2_transfer(dln2->pdev, cmd, &req, sizeof(req), &rsp, &len);
+	if (ret < 0)
+		return ret;
+
+	if (len < sizeof(rsp) || req.pin != rsp.pin)
+		return -EPROTO;
+
+	return rsp.value;
+}
+
+static int dln2_gpio_pin_get_in_val(struct dln2_gpio *dln2, unsigned int pin)
+{
+	int ret = dln2_gpio_pin_val(dln2, DLN2_GPIO_PIN_GET_VAL, pin);
+
+	if (ret < 0)
+		return ret;
+	return !!ret;
+}
+
+static int dln2_gpio_pin_get_out_val(struct dln2_gpio *dln2, unsigned int pin)
+{
+	int ret = dln2_gpio_pin_val(dln2, DLN2_GPIO_PIN_GET_OUT_VAL, pin);
+
+	if (ret < 0)
+		return ret;
+	return !!ret;
+}
+
+static void dln2_gpio_pin_set_out_val(struct dln2_gpio *dln2,
+				      unsigned int pin, int value)
+{
+	struct dln2_gpio_pin_val req = {
+		.pin = cpu_to_le16(pin),
+		.value = cpu_to_le16(value),
+	};
+
+	dln2_transfer(dln2->pdev, DLN2_GPIO_PIN_SET_OUT_VAL, &req, sizeof(req),
+		      NULL, NULL);
+}
+
+static int dln2_gpio_request(struct gpio_chip *chip, unsigned offset)
+{
+	struct dln2_gpio *dln2 = container_of(chip, struct dln2_gpio, gpio);
+
+	return dln2_gpio_pin_cmd(dln2, DLN2_GPIO_PIN_ENABLE, offset);
+}
+
+static void dln2_gpio_free(struct gpio_chip *chip, unsigned offset)
+{
+	struct dln2_gpio *dln2 = container_of(chip, struct dln2_gpio, gpio);
+
+	dln2_gpio_pin_cmd(dln2, DLN2_GPIO_PIN_DISABLE, offset);
+}
+
+#define DLN2_GPIO_DIRECTION_IN		0
+#define DLN2_GPIO_DIRECTION_OUT		1
+
+static int dln2_gpio_get_direction(struct gpio_chip *chip, unsigned offset)
+{
+	struct dln2_gpio *dln2 = container_of(chip, struct dln2_gpio, gpio);
+	struct dln2_gpio_pin req = {
+		.pin = cpu_to_le16(offset),
+	};
+	struct dln2_gpio_pin_val rsp;
+	int ret, len = sizeof(rsp);
+
+	ret = dln2_transfer(dln2->pdev, DLN2_GPIO_PIN_GET_DIRECTION,
+			    &req, sizeof(req), &rsp, &len);
+	if (ret < 0)
+		return ret;
+
+	if (len < sizeof(rsp) || req.pin != rsp.pin)
+		return -EPROTO;
+
+	switch (rsp.value) {
+	case DLN2_GPIO_DIRECTION_IN:
+		return 1;
+	case DLN2_GPIO_DIRECTION_OUT:
+		return 0;
+	default:
+		return -EPROTO;
+	}
+}
+
+static int dln2_gpio_get(struct gpio_chip *chip, unsigned int offset)
+{
+	struct dln2_gpio *dln2 = container_of(chip, struct dln2_gpio, gpio);
+	int dir = dln2_gpio_get_direction(chip, offset);
+
+	if (dir < 0)
+		return dir;
+
+	if (dir)
+		return dln2_gpio_pin_get_in_val(dln2, offset);
+
+	return dln2_gpio_pin_get_out_val(dln2, offset);
+}
+
+static void dln2_gpio_set(struct gpio_chip *chip, unsigned offset, int value)
+{
+	struct dln2_gpio *dln2 = container_of(chip, struct dln2_gpio, gpio);
+
+	dln2_gpio_pin_set_out_val(dln2, offset, value);
+}
+
+static int dln2_gpio_set_direction(struct gpio_chip *chip, unsigned offset,
+				   unsigned dir)
+{
+	struct dln2_gpio *dln2 = container_of(chip, struct dln2_gpio, gpio);
+	struct dln2_gpio_pin_val req = {
+		.pin = cpu_to_le16(offset),
+		.value = cpu_to_le16(dir),
+	};
+
+	return dln2_transfer(dln2->pdev, DLN2_GPIO_PIN_SET_DIRECTION,
+			     &req, sizeof(req), NULL, NULL);
+}
+
+static int dln2_gpio_direction_input(struct gpio_chip *chip, unsigned offset)
+{
+	return dln2_gpio_set_direction(chip, offset, DLN2_GPIO_DIRECTION_IN);
+}
+
+static int dln2_gpio_direction_output(struct gpio_chip *chip, unsigned offset,
+				      int value)
+{
+	return dln2_gpio_set_direction(chip, offset, DLN2_GPIO_DIRECTION_OUT);
+}
+
+static int dln2_gpio_set_debounce(struct gpio_chip *chip, unsigned offset,
+				  unsigned debounce)
+{
+	struct dln2_gpio *dln2 = container_of(chip, struct dln2_gpio, gpio);
+	struct {
+		__le32 duration;
+	} __packed req = {
+		.duration = cpu_to_le32(debounce),
+	};
+
+	return dln2_transfer(dln2->pdev, DLN2_GPIO_SET_DEBOUNCE,
+			     &req, sizeof(req), NULL, NULL);
+}
+
+static int dln2_gpio_set_event_cfg(struct dln2_gpio *dln2, unsigned pin,
+				   unsigned type, unsigned period)
+{
+	struct {
+		__le16 pin;
+		u8 type;
+		__le16 period;
+	} __packed req = {
+		.pin = cpu_to_le16(pin),
+		.type = type,
+		.period = cpu_to_le16(period),
+	};
+
+	return dln2_transfer(dln2->pdev, DLN2_GPIO_PIN_SET_EVENT_CFG,
+			     &req, sizeof(req), NULL, NULL);
+}
+
+static void dln2_irq_work(struct work_struct *w)
+{
+	struct dln2_irq_work *iw = container_of(w, struct dln2_irq_work, work);
+	struct dln2_gpio *dln2 = iw->dln2;
+	u8 type = iw->type & DLN2_GPIO_EVENT_MASK;
+
+	if (test_bit(iw->pin, dln2->irqs_enabled))
+		dln2_gpio_set_event_cfg(dln2, iw->pin, type, 0);
+	else
+		dln2_gpio_set_event_cfg(dln2, iw->pin, DLN2_GPIO_EVENT_NONE, 0);
+}
+
+static void dln2_irq_enable(struct irq_data *irqd)
+{
+	struct gpio_chip *gc = irq_data_get_irq_chip_data(irqd);
+	struct dln2_gpio *dln2 = container_of(gc, struct dln2_gpio, gpio);
+	int pin = irqd_to_hwirq(irqd);
+
+	set_bit(pin, dln2->irqs_enabled);
+	schedule_work(&dln2->irq_work[pin].work);
+}
+
+static void dln2_irq_disable(struct irq_data *irqd)
+{
+	struct gpio_chip *gc = irq_data_get_irq_chip_data(irqd);
+	struct dln2_gpio *dln2 = container_of(gc, struct dln2_gpio, gpio);
+	int pin = irqd_to_hwirq(irqd);
+
+	clear_bit(pin, dln2->irqs_enabled);
+	schedule_work(&dln2->irq_work[pin].work);
+}
+
+static void dln2_irq_mask(struct irq_data *irqd)
+{
+	struct gpio_chip *gc = irq_data_get_irq_chip_data(irqd);
+	struct dln2_gpio *dln2 = container_of(gc, struct dln2_gpio, gpio);
+	int pin = irqd_to_hwirq(irqd);
+
+	set_bit(pin, dln2->irqs_masked);
+}
+
+static void dln2_irq_unmask(struct irq_data *irqd)
+{
+	struct gpio_chip *gc = irq_data_get_irq_chip_data(irqd);
+	struct dln2_gpio *dln2 = container_of(gc, struct dln2_gpio, gpio);
+	int pin = irqd_to_hwirq(irqd);
+
+	if (test_and_clear_bit(pin, dln2->irqs_pending))
+		generic_handle_irq(pin);
+}
+
+static int dln2_irq_set_type(struct irq_data *irqd, unsigned type)
+{
+	struct gpio_chip *gc = irq_data_get_irq_chip_data(irqd);
+	struct dln2_gpio *dln2 = container_of(gc, struct dln2_gpio, gpio);
+	int pin = irqd_to_hwirq(irqd);
+
+	switch (type) {
+	case IRQ_TYPE_LEVEL_HIGH:
+		dln2->irq_work[pin].type = DLN2_GPIO_EVENT_LVL_HIGH;
+		break;
+	case IRQ_TYPE_LEVEL_LOW:
+		dln2->irq_work[pin].type = DLN2_GPIO_EVENT_LVL_LOW;
+		break;
+	case IRQ_TYPE_EDGE_BOTH:
+		dln2->irq_work[pin].type = DLN2_GPIO_EVENT_CHANGE;
+		break;
+	case IRQ_TYPE_EDGE_RISING:
+		dln2->irq_work[pin].type = DLN2_GPIO_EVENT_CHANGE_RISING;
+		break;
+	case IRQ_TYPE_EDGE_FALLING:
+		dln2->irq_work[pin].type = DLN2_GPIO_EVENT_CHANGE_FALLING;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static struct irq_chip dln2_gpio_irqchip = {
+	.name = "dln2-irq",
+	.irq_enable = dln2_irq_enable,
+	.irq_disable = dln2_irq_disable,
+	.irq_mask = dln2_irq_mask,
+	.irq_unmask = dln2_irq_unmask,
+	.irq_set_type = dln2_irq_set_type,
+};
+
+static void dln2_gpio_event(struct platform_device *pdev, u16 echo,
+			    const void *data, int len)
+{
+	int pin, irq;
+	const struct {
+		__le16 count;
+		__u8 type;
+		__le16 pin;
+		__u8 value;
+	} __packed *event = data;
+	struct dln2_gpio *dln2 = platform_get_drvdata(pdev);
+
+	pin = le16_to_cpu(event->pin);
+	irq = irq_find_mapping(dln2->gpio.irqdomain, pin);
+
+	if (!irq) {
+		dev_err(dln2->gpio.dev, "pin %d not mapped to IRQ\n", pin);
+		return;
+	}
+
+	if (!test_bit(pin, dln2->irqs_enabled))
+		return;
+	if (test_bit(pin, dln2->irqs_masked)) {
+		set_bit(pin, dln2->irqs_pending);
+		return;
+	}
+
+	switch (dln2->irq_work[pin].type) {
+	case DLN2_GPIO_EVENT_CHANGE_RISING:
+		if (event->value)
+			generic_handle_irq(irq);
+		break;
+	case DLN2_GPIO_EVENT_CHANGE_FALLING:
+		if (!event->value)
+			generic_handle_irq(irq);
+		break;
+	default:
+		generic_handle_irq(irq);
+	}
+}
+
+static int dln2_do_remove(struct dln2_gpio *dln2)
+{
+	/* When removing the DLN2 USB device, gpiochip_remove may fail
+	 * due to i2c drivers holding a GPIO pin. However, the i2c bus
+	 * will eventually be removed triggering an i2c driver remove
+	 * which will release the GPIO pin. So retrying the operation
+	 * later should succeed. */
+	int ret = gpiochip_remove(&dln2->gpio);
+	struct device *dev = dln2->gpio.dev;
+
+	if (ret < 0) {
+		if (ret == -EBUSY)
+			schedule_delayed_work(&dln2->remove_work.work, HZ/10);
+		else
+			dev_warn(dev, "error removing gpio chip: %d\n", ret);
+	} else {
+		kfree(dln2);
+	}
+
+	return ret;
+}
+
+static void dln2_remove_work(struct work_struct *w)
+{
+	struct delayed_work *dw = to_delayed_work(w);
+	struct dln2_remove_work *rw = container_of(dw, struct dln2_remove_work,
+						   work);
+	struct dln2_gpio *dln2 = rw->dln2;
+
+	dln2_do_remove(dln2);
+}
+
+static int dln2_gpio_probe(struct platform_device *pdev)
+{
+	struct dln2_gpio *dln2;
+	struct device *dev = &pdev->dev;
+	int pins = dln2_gpio_get_pin_count(pdev), i, ret;
+
+	if (pins < 0) {
+		dev_err(dev, "failed to get pin count: %d\n", pins);
+		return pins;
+	}
+	if (pins > DLN2_GPIO_MAX_PINS)
+		dev_warn(dev, "clamping pins to %d\n", DLN2_GPIO_MAX_PINS);
+
+	dln2 = kzalloc(sizeof(*dln2), GFP_KERNEL);
+	if (!dln2)
+		return -ENOMEM;
+
+	for (i = 0; i < DLN2_GPIO_MAX_PINS; i++) {
+		INIT_WORK(&dln2->irq_work[i].work, dln2_irq_work);
+		dln2->irq_work[i].pin = i;
+		dln2->irq_work[i].dln2 = dln2;
+	}
+	INIT_DELAYED_WORK(&dln2->remove_work.work, dln2_remove_work);
+	dln2->remove_work.dln2 = dln2;
+
+	ret = dln2_register_event_cb(pdev, DLN2_GPIO_CONDITION_MET_EV,
+				     dln2_gpio_event);
+	if (ret) {
+		kfree(dln2);
+		return ret;
+	}
+
+	dln2->pdev = pdev;
+
+	dln2->gpio.label = "dln2";
+	dln2->gpio.dev = dev;
+	dln2->gpio.owner = THIS_MODULE;
+	dln2->gpio.base = -1;
+	dln2->gpio.ngpio = pins;
+	dln2->gpio.exported = 1;
+	dln2->gpio.set = dln2_gpio_set;
+	dln2->gpio.get = dln2_gpio_get;
+	dln2->gpio.request = dln2_gpio_request;
+	dln2->gpio.free = dln2_gpio_free;
+	dln2->gpio.get_direction = dln2_gpio_get_direction;
+	dln2->gpio.direction_input = dln2_gpio_direction_input;
+	dln2->gpio.direction_output = dln2_gpio_direction_output;
+	dln2->gpio.set_debounce = dln2_gpio_set_debounce;
+
+	ret = gpiochip_add(&dln2->gpio);
+	if (ret < 0) {
+		dev_err(dev, "failed to add gpio chip: %d\n", ret);
+		dln2_unregister_event_cb(pdev, DLN2_GPIO_CONDITION_MET_EV);
+		kfree(dln2);
+		return ret;
+	}
+
+	ret = gpiochip_irqchip_add(&dln2->gpio, &dln2_gpio_irqchip, 0,
+				   handle_simple_irq, IRQ_TYPE_NONE);
+	if (ret < 0) {
+		dev_err(dev, "failed to add irq chip: %d\n", ret);
+		dln2_unregister_event_cb(pdev, DLN2_GPIO_CONDITION_MET_EV);
+		gpiochip_remove(&dln2->gpio);
+		kfree(dln2);
+		return ret;
+	}
+
+	platform_set_drvdata(pdev, dln2);
+
+	return 0;
+}
+
+static int dln2_gpio_remove(struct platform_device *pdev)
+{
+	struct dln2_gpio *dln2 = platform_get_drvdata(pdev);
+
+	dln2_unregister_event_cb(pdev, DLN2_GPIO_CONDITION_MET_EV);
+	dln2->pdev = NULL;
+
+	return dln2_do_remove(dln2);
+}
+
+static struct platform_driver dln2_gpio_driver = {
+	.driver.name	= DRIVER_NAME,
+	.driver.owner	= THIS_MODULE,
+	.probe		= dln2_gpio_probe,
+	.remove		= dln2_gpio_remove,
+};
+
+module_platform_driver(dln2_gpio_driver);
+
+MODULE_AUTHOR("Daniel Baluta <daniel.baluta-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org");
+MODULE_DESCRIPTION(DRIVER_NAME "driver");
+MODULE_LICENSE("GPL");
-- 
1.9.1