extcon: usb-gpio: Introduce gpio usb extcon driver

This driver observes the USB ID pin connected over a GPIO and
updates the USB cable extcon states accordingly.

The existing GPIO extcon driver is not suitable for this purpose
as it needs to be taught to understand USB cable states and it
can't handle more than one cable per instance.

For the USB case we need to handle 2 cable states.
1) USB (attach/detach)
2) USB-HOST (attach/detach)

This driver can be easily updated in the future to handle VBUS
events in case it happens to be available on GPIO for any platform.

Signed-off-by: Roger Quadros <rogerq@ti.com>
Reviewed-by: Felipe Balbi <balbi@ti.com>
Acked-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>

3 files changed, 245 insertions, 0 deletions

diff --git a/drivers/extcon/Kconfig b/drivers/extcon/Kconfig
index 6a1f7de6fa54..e4c01ab046f7 100644
--- a/drivers/extcon/Kconfig
+++ b/drivers/extcon/Kconfig
@@ -93,4 +93,11 @@ config EXTCON_SM5502
           Silicon Mitus SM5502. The SM5502 is a USB port accessory
           detector and switch.
 
+config EXTCON_USB_GPIO
+        tristate "USB GPIO extcon support"
+        depends on GPIOLIB
+        help
+          Say Y here to enable GPIO based USB cable detection extcon support.
+          Used typically if GPIO is used for USB ID pin detection.
+
 endif # MULTISTATE_SWITCH
diff --git a/drivers/extcon/Makefile b/drivers/extcon/Makefile
index 0370b42e5a27..6a08a98dc069 100644
--- a/drivers/extcon/Makefile
+++ b/drivers/extcon/Makefile
@@ -12,3 +12,4 @@ obj-$(CONFIG_EXTCON_MAX8997)	+= extcon-max8997.o
 obj-$(CONFIG_EXTCON_PALMAS)     += extcon-palmas.o
 obj-$(CONFIG_EXTCON_RT8973A)    += extcon-rt8973a.o
 obj-$(CONFIG_EXTCON_SM5502)     += extcon-sm5502.o
+obj-$(CONFIG_EXTCON_USB_GPIO)   += extcon-usb-gpio.o
diff --git a/drivers/extcon/extcon-usb-gpio.c b/drivers/extcon/extcon-usb-gpio.c
new file mode 100644
index 000000000000..3f0bad3ce8aa
--- /dev/null
+++ b/drivers/extcon/extcon-usb-gpio.c
@@ -0,0 +1,237 @@
+/**
+ * drivers/extcon/extcon-usb-gpio.c - USB GPIO extcon driver
+ *
+ * Copyright (C) 2015 Texas Instruments Incorporated - http://www.ti.com
+ * Author: Roger Quadros <rogerq@ti.com>
+ *
+ * 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.
+ */
+
+#include <linux/extcon.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of_gpio.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/workqueue.h>
+
+#define USB_GPIO_DEBOUNCE_MS    20      /* ms */
+
+struct usb_extcon_info {
+        struct device *dev;
+        struct extcon_dev *edev;
+
+        struct gpio_desc *id_gpiod;
+        int id_irq;
+
+        unsigned long debounce_jiffies;
+        struct delayed_work wq_detcable;
+};
+
+/* List of detectable cables */
+enum {
+        EXTCON_CABLE_USB = 0,
+        EXTCON_CABLE_USB_HOST,
+
+        EXTCON_CABLE_END,
+};
+
+static const char *usb_extcon_cable[] = {
+        [EXTCON_CABLE_USB] = "USB",
+        [EXTCON_CABLE_USB_HOST] = "USB-HOST",
+        NULL,
+};
+
+static void usb_extcon_detect_cable(struct work_struct *work)
+{
+        int id;
+        struct usb_extcon_info *info = container_of(to_delayed_work(work),
+                                                    struct usb_extcon_info,
+                                                    wq_detcable);
+
+        /* check ID and update cable state */
+        id = gpiod_get_value_cansleep(info->id_gpiod);
+        if (id) {
+                /*
+                 * ID = 1 means USB HOST cable detached.
+                 * As we don't have event for USB peripheral cable attached,
+                 * we simulate USB peripheral attach here.
+                 */
+                extcon_set_cable_state(info->edev,
+                                       usb_extcon_cable[EXTCON_CABLE_USB_HOST],
+                                       false);
+                extcon_set_cable_state(info->edev,
+                                       usb_extcon_cable[EXTCON_CABLE_USB],
+                                       true);
+        } else {
+                /*
+                 * ID = 0 means USB HOST cable attached.
+                 * As we don't have event for USB peripheral cable detached,
+                 * we simulate USB peripheral detach here.
+                 */
+                extcon_set_cable_state(info->edev,
+                                       usb_extcon_cable[EXTCON_CABLE_USB],
+                                       false);
+                extcon_set_cable_state(info->edev,
+                                       usb_extcon_cable[EXTCON_CABLE_USB_HOST],
+                                       true);
+        }
+}
+
+static irqreturn_t usb_irq_handler(int irq, void *dev_id)
+{
+        struct usb_extcon_info *info = dev_id;
+
+        queue_delayed_work(system_power_efficient_wq, &info->wq_detcable,
+                           info->debounce_jiffies);
+
+        return IRQ_HANDLED;
+}
+
+static int usb_extcon_probe(struct platform_device *pdev)
+{
+        struct device *dev = &pdev->dev;
+        struct device_node *np = dev->of_node;
+        struct usb_extcon_info *info;
+        int ret;
+
+        if (!np)
+                return -EINVAL;
+
+        info = devm_kzalloc(&pdev->dev, sizeof(*info), GFP_KERNEL);
+        if (!info)
+                return -ENOMEM;
+
+        info->dev = dev;
+        info->id_gpiod = devm_gpiod_get(&pdev->dev, "id");
+        if (IS_ERR(info->id_gpiod)) {
+                dev_err(dev, "failed to get ID GPIO\n");
+                return PTR_ERR(info->id_gpiod);
+        }
+
+        ret = gpiod_set_debounce(info->id_gpiod,
+                                 USB_GPIO_DEBOUNCE_MS * 1000);
+        if (ret < 0)
+                info->debounce_jiffies = msecs_to_jiffies(USB_GPIO_DEBOUNCE_MS);
+
+        INIT_DELAYED_WORK(&info->wq_detcable, usb_extcon_detect_cable);
+
+        info->id_irq = gpiod_to_irq(info->id_gpiod);
+        if (info->id_irq < 0) {
+                dev_err(dev, "failed to get ID IRQ\n");
+                return info->id_irq;
+        }
+
+        ret = devm_request_threaded_irq(dev, info->id_irq, NULL,
+                                        usb_irq_handler,
+                                        IRQF_TRIGGER_RISING |
+                                        IRQF_TRIGGER_FALLING | IRQF_ONESHOT,
+                                        pdev->name, info);
+        if (ret < 0) {
+                dev_err(dev, "failed to request handler for ID IRQ\n");
+                return ret;
+        }
+
+        info->edev = devm_extcon_dev_allocate(dev, usb_extcon_cable);
+        if (IS_ERR(info->edev)) {
+                dev_err(dev, "failed to allocate extcon device\n");
+                return -ENOMEM;
+        }
+
+        ret = devm_extcon_dev_register(dev, info->edev);
+        if (ret < 0) {
+                dev_err(dev, "failed to register extcon device\n");
+                return ret;
+        }
+
+        platform_set_drvdata(pdev, info);
+        device_init_wakeup(dev, 1);
+
+        /* Perform initial detection */
+        usb_extcon_detect_cable(&info->wq_detcable.work);
+