gpio: add support for the Diolan DLN-2 USB GPIO driver

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@intel.com>
Signed-off-by: Octavian Purdila <octavian.purdila@intel.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

3 files changed, 566 insertions, 0 deletions

diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 0959ca9b6b27..23dfd5f59b39 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -905,4 +905,16 @@ 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 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 e5d346cf3b6e..e60677b8ccb4 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 000000000000..978b51eae2ec
--- /dev/null
+++ b/drivers/gpio/gpio-dln2.c
@@ -0,0 +1,553 @@
+/*
+ * 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/module.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+#include <linux/irqdomain.h>
+#include <linux/irq.h>
+#include <linux/irqchip/chained_irq.h>
+#include <linux/gpio.h>
+#include <linux/gpio/driver.h>
+#include <linux/platform_device.h>
+#include <linux/mfd/dln2.h>
+
+#define DLN2_GPIO_ID                    0x01
+
+#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;
+        int type;
+};
+
+struct dln2_gpio {
+        struct platform_device *pdev;
+        struct gpio_chip gpio;
+
+        /*
+         * Cache pin direction to save us one transfer, since the hardware has
+         * separate commands to read the in and out values.
+         */
+        DECLARE_BITMAP(output_enabled, DLN2_GPIO_MAX_PINS);
+
+        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;
+};
+
+struct dln2_gpio_pin {
+        __le16 pin;
+};
+
+struct dln2_gpio_pin_val {
+        __le16 pin __packed;
+        u8 value;
+};
+
+static int dln2_gpio_get_pin_count(struct platform_device *pdev)
+{
+        int ret;
+        __le16 count;
+        int len = sizeof(count);
+
+        ret = dln2_transfer_rx(pdev, DLN2_GPIO_GET_PIN_COUNT, &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_tx(dln2->pdev, cmd, &req, sizeof(req));
+}
+
+static int dln2_gpio_pin_val(struct dln2_gpio *dln2, int cmd, unsigned int pin)
+{
+        int ret;
+        struct dln2_gpio_pin req = {
+                .pin = cpu_to_le16(pin),
+        };
+        struct dln2_gpio_pin_val rsp;
+        int 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;
+
+        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;
+
+        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 = value,
+        };
+
+        dln2_transfer_tx(dln2->pdev, DLN2_GPIO_PIN_SET_OUT_VAL, &req,
+                         sizeof(req));
+}
+
+#define DLN2_GPIO_DIRECTION_IN          0
+#define DLN2_GPIO_DIRECTION_OUT         1
+
+static int dln2_gpio_request(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 len = sizeof(rsp);
+        int ret;
+
+        ret = dln2_gpio_pin_cmd(dln2, DLN2_GPIO_PIN_ENABLE, offset);
+        if (ret < 0)
+                return ret;
+
+        /* cache the pin direction */
+        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) {
+                ret = -EPROTO;
+                goto out_disable;
+        }
+
+        switch (rsp.value) {
+        case DLN2_GPIO_DIRECTION_IN:
+                clear_bit(offset, dln2->output_enabled);
+                return 0;
+        case DLN2_GPIO_DIRECTION_OUT:
+                set_bit(offset, dln2->output_enabled);
+                return 0;
+        default:
+                ret = -EPROTO;
+                goto out_disable;
+        }
+
+out_disable:
+        dln2_gpio_pin_cmd(dln2, DLN2_GPIO_PIN_DISABLE, offset);
+        return ret;
+}
+
+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);
+}
+
+static int dln2_gpio_get_direction(struct gpio_chip *chip, unsigned offset)
+{
+        struct dln2_gpio *dln2 = container_of(chip, struct dln2_gpio, gpio);
+
+        if (test_bit(offset, dln2->output_enabled))
+                return GPIOF_DIR_OUT;
+
+        return GPIOF_DIR_IN;
+}
+
+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;
+
+        dir = dln2_gpio_get_direction(chip, offset);
+        if (dir < 0)
+                return dir;
+
+        if (dir == GPIOF_DIR_IN)
+                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 = dir,
+        };
+        int ret;
+
+        ret = dln2_transfer_tx(dln2->pdev, DLN2_GPIO_PIN_SET_DIRECTION,
+                               &req, sizeof(req));
+        if (ret < 0)
+                return ret;
+
+        if (dir == DLN2_GPIO_DIRECTION_OUT)
+                set_bit(offset, dln2->output_enabled);
+        else
+                clear_bit(offset, dln2->output_enabled);
+
+        return ret;
+}
+
+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);
+        __le32 duration = cpu_to_le32(debounce);
+
+        return dln2_transfer_tx(dln2->pdev, DLN2_GPIO_SET_DEBOUNCE,
+                                &duration, sizeof(duration));
+}
+
+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_tx(dln2->pdev, DLN2_GPIO_PIN_SET_EVENT_CFG,
+                                &req, sizeof(req));
+}
+
+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);
+        struct device *dev = dln2->gpio.dev;
+        int pin = irqd_to_hwirq(irqd);
+
+        if (test_and_clear_bit(pin, dln2->irqs_pending)) {
+                int irq;
+
+                irq = irq_find_mapping(dln2->gpio.irqdomain, pin);
+                if (!irq) {
+                        dev_err(dev, "pin %d not mapped to IRQ\n", pin);
+                        return;
+                }
+
+                generic_handle_irq(irq);
+        }
+}
+
+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);
+
+        if (len < sizeof(*event)) {
+                dev_err(dln2->gpio.dev, "short event message\n");
+                return;
+        }
+
+        pin = le16_to_cpu(event->pin);
+        if (pin >= dln2->gpio.ngpio) {
+                dev_err(dln2->gpio.dev, "out of bounds pin %d\n", pin);
+                return;
+        }
+
+        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_gpio_probe(struct platform_device *pdev)
+{
+        struct dln2_gpio *dln2;
+        struct device *dev = &pdev->dev;
+        int pins;
+        int i, ret;
+
+        pins = dln2_gpio_get_pin_count(pdev);
+        if (pins < 0) {
+                dev_err(dev, "failed to get pin count: %d\n", pins);
+                return pins;
+        }
+        if (pins > DLN2_GPIO_MAX_PINS) {
+                pins = DLN2_GPIO_MAX_PINS;
+                dev_warn(dev, "clamping pins to %d\n", DLN2_GPIO_MAX_PINS);
+        }
+
+        dln2 = devm_kzalloc(&pdev->dev, sizeof(*dln2), GFP_KERNEL);
+        if (!dln2)
+                return -ENOMEM;
+
+        dln2->irq_work = devm_kcalloc(&pdev->dev, pins,
+                                      sizeof(struct dln2_irq_work), GFP_KERNEL);
+        if (!dln2->irq_work)
+                return -ENOMEM;
+        for (i = 0; i < pins; i++) {
+                INIT_WORK(&dln2->irq_work[i].work, dln2_irq_work);
+                dln2->irq_work[i].pin = i;
+                dln2->irq_work[i].dln2 = dln2;
+        }
+
+        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 = true;
+        dln2->gpio.can_sleep = true;
+        dln2->gpio.irq_not_threaded = true;
+        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;
+
+        platform_set_drvdata(pdev, dln2);
+
+        ret = gpiochip_add(&dln2->gpio);
+        if (ret < 0) {
+                dev_err(dev, "failed to add gpio chip: %d\n", ret);
+                goto out;
+        }
+
+        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);
+                goto out_gpiochip_remove;
+        }
+
+        ret = dln2_register_event_cb(pdev, DLN2_GPIO_CONDITION_MET_EV,
+                                     dln2_gpio_event);
+        if (ret) {
+                dev_err(dev, "failed to register event cb: %d\n", ret);
+                goto out_gpiochip_remove;
+        }
+
+        return 0;
+
+out_gpiochip_remove:
+        gpiochip_remove(&dln2->gpio);
+out:
+        return ret;
+}
+
+static int dln2_gpio_remove(struct platform_device *pdev)
+{
+        struct dln2_gpio *dln2 = platform_get_drvdata(pdev);
+        int i;
+
+        dln2_unregister_event_cb(pdev, DLN2_GPIO_CONDITION_MET_EV);
+        for (i = 0; i < dln2->gpio.ngpio; i++)
+                flush_work(&dln2->irq_work[i].work);
+        gpiochip_remove(&dln2->gpio);
+
+        return 0;
+}
+
+static struct platform_driver dln2_gpio_driver = {
+        .driver.name    = "dln2-gpio",
+        .probe          = dln2_gpio_probe,
+        .remove         = dln2_gpio_remove,
+};
+
+module_platform_driver(dln2_gpio_driver);
+
+MODULE_AUTHOR("Daniel Baluta <daniel.baluta@intel.com");
+MODULE_DESCRIPTION("Driver for the Diolan DLN2 GPIO interface");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("platform:dln2-gpio");