4 files changed, 212 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/gpio/gpio-restart.txt b/Documentation/devicetree/bindings/gpio/gpio-restart.txt
new file mode 100644
index 000000000000..af3701bc15c4
--- /dev/null
+++ b/Documentation/devicetree/bindings/gpio/gpio-restart.txt
@@ -0,0 +1,54 @@
+Drive a GPIO line that can be used to restart the system from a restart
+handler.
+
+This binding supports level and edge triggered reset.  At driver load
+time, the driver will request the given gpio line and install a restart
+handler. If the optional properties 'open-source' is not found, the GPIO line
+will be driven in the inactive state.  Otherwise its not driven until
+the restart is initiated.
+
+When the system is restarted, the restart handler will be invoked in
+priority order.  The gpio is configured as an output, and driven active,
+triggering a level triggered reset condition. This will also cause an
+inactive->active edge condition, triggering positive edge triggered
+reset. After a delay specified by active-delay, the GPIO is set to
+inactive, thus causing an active->inactive edge, triggering negative edge
+triggered reset. After a delay specified by inactive-delay, the GPIO
+is driven active again.  After a delay specified by wait-delay, the
+restart handler completes allowing other restart handlers to be attempted.
+
+Required properties:
+- compatible : should be "gpio-restart".
+- gpios : The GPIO to set high/low, see "gpios property" in
+  Documentation/devicetree/bindings/gpio/gpio.txt. If the pin should be
+  low to reset the board set it to "Active Low", otherwise set
+  gpio to "Active High".
+
+Optional properties:
+- open-source : Treat the GPIO as being open source and defer driving
+  it to when the restart is initiated.  If this optional property is not
+  specified, the GPIO is initialized as an output in its inactive state.
+- priority : A priority ranging from 0 to 255 (default 128) according to
+  the following guidelines:
+        0:      Restart handler of last resort, with limited restart
+                capabilities
+        128:    Default restart handler; use if no other restart handler is
+                expected to be available, and/or if restart functionality is
+                sufficient to restart the entire system
+        255:    Highest priority restart handler, will preempt all other
+                restart handlers
+- active-delay: Delay (default 100) to wait after driving gpio active [ms]
+- inactive-delay: Delay (default 100) to wait after driving gpio inactive [ms]
+- wait-delay: Delay (default 3000) to wait after completing restart
+  sequence [ms]
+
+Examples:
+
+gpio-restart {
+        compatible = "gpio-restart";
+        gpios = <&gpio 4 0>;
+        priority = <128>;
+        active-delay = <100>;
+        inactive-delay = <100>;
+        wait-delay = <3000>;
+};
diff --git a/drivers/power/reset/Kconfig b/drivers/power/reset/Kconfig
index 88603b6990ed..a178e9c50a20 100644
--- a/drivers/power/reset/Kconfig
+++ b/drivers/power/reset/Kconfig
@@ -39,6 +39,14 @@ config POWER_RESET_GPIO
           If your board needs a GPIO high/low to power down, say Y and
           create a binding in your devicetree.
 
+config POWER_RESET_GPIO_RESTART
+        bool "GPIO restart driver"
+        depends on OF_GPIO && POWER_RESET
+        help
+          This driver supports restarting your board via a GPIO line.
+          If your board needs a GPIO high/low to restart, say Y and
+          create a binding in your devicetree.
+
 config POWER_RESET_HISI
         bool "Hisilicon power-off driver"
         depends on POWER_RESET && ARCH_HISI
diff --git a/drivers/power/reset/Makefile b/drivers/power/reset/Makefile
index 06f106b6cfc8..ab8cd348a099 100644
--- a/drivers/power/reset/Makefile
+++ b/drivers/power/reset/Makefile
@@ -2,6 +2,7 @@ obj-$(CONFIG_POWER_RESET_AS3722) += as3722-poweroff.o
 obj-$(CONFIG_POWER_RESET_AXXIA) += axxia-reset.o
 obj-$(CONFIG_POWER_RESET_BRCMSTB) += brcmstb-reboot.o
 obj-$(CONFIG_POWER_RESET_GPIO) += gpio-poweroff.o
+obj-$(CONFIG_POWER_RESET_GPIO_RESTART) += gpio-restart.o
 obj-$(CONFIG_POWER_RESET_HISI) += hisi-reboot.o
 obj-$(CONFIG_POWER_RESET_MSM) += msm-poweroff.o
 obj-$(CONFIG_POWER_RESET_LTC2952) += ltc2952-poweroff.o
diff --git a/drivers/power/reset/gpio-restart.c b/drivers/power/reset/gpio-restart.c
new file mode 100644
index 000000000000..a76829b3f1cd
--- /dev/null
+++ b/drivers/power/reset/gpio-restart.c
@@ -0,0 +1,149 @@
+/*
+ * Toggles a GPIO pin to restart a device
+ *
+ * Copyright (C) 2014 Google, Inc.
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * 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.
+ *
+ * Based on the gpio-poweroff driver.
+ */
+#include <linux/reboot.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/delay.h>
+#include <linux/platform_device.h>
+#include <linux/gpio/consumer.h>
+#include <linux/of_platform.h>
+#include <linux/module.h>
+
+struct gpio_restart {
+        struct gpio_desc *reset_gpio;
+        struct notifier_block restart_handler;
+        u32 active_delay_ms;
+        u32 inactive_delay_ms;
+        u32 wait_delay_ms;
+};
+
+static int gpio_restart_notify(struct notifier_block *this,
+                                unsigned long mode, void *cmd)
+{
+        struct gpio_restart *gpio_restart =
+                container_of(this, struct gpio_restart, restart_handler);
+
+        /* drive it active, also inactive->active edge */
+        gpiod_direction_output(gpio_restart->reset_gpio, 1);
+        mdelay(gpio_restart->active_delay_ms);
+
+        /* drive inactive, also active->inactive edge */
+        gpiod_set_value(gpio_restart->reset_gpio, 0);
+        mdelay(gpio_restart->inactive_delay_ms);
+
+        /* drive it active, also inactive->active edge */
+        gpiod_set_value(gpio_restart->reset_gpio, 1);
+
+        /* give it some time */
+        mdelay(gpio_restart->wait_delay_ms);
+
+        WARN_ON(1);
+
+        return NOTIFY_DONE;
+}
+
+static int gpio_restart_probe(struct platform_device *pdev)
+{
+        struct gpio_restart *gpio_restart;
+        bool open_source = false;
+        u32 property;
+        int ret;
+
+        gpio_restart = devm_kzalloc(&pdev->dev, sizeof(*gpio_restart),
+                        GFP_KERNEL);
+        if (!gpio_restart)
+                return -ENOMEM;
+
+        open_source = of_property_read_bool(pdev->dev.of_node, "open-source");
+
+        gpio_restart->reset_gpio = devm_gpiod_get(&pdev->dev, NULL,
+                        open_source ? GPIOD_IN : GPIOD_OUT_LOW);
+        if (IS_ERR(gpio_restart->reset_gpio)) {
+                dev_err(&pdev->dev, "Could net get reset GPIO\n");
+                return PTR_ERR(gpio_restart->reset_gpio);
+        }
+
+        gpio_restart->restart_handler.notifier_call = gpio_restart_notify;
+        gpio_restart->restart_handler.priority = 128;
+        gpio_restart->active_delay_ms = 100;
+        gpio_restart->inactive_delay_ms = 100;
+        gpio_restart->wait_delay_ms = 3000;
+
+        ret = of_property_read_u32(pdev->dev.of_node, "priority", &property);
+        if (!ret) {
+                if (property > 255)
+                        dev_err(&pdev->dev, "Invalid priority property: %u\n",
+                                        property);
+                else
+                        gpio_restart->restart_handler.priority = property;
+        }
+
+        of_property_read_u32(pdev->dev.of_node, "active-delay",
+                        &gpio_restart->active_delay_ms);
+        of_property_read_u32(pdev->dev.of_node, "inactive-delay",
+                        &gpio_restart->inactive_delay_ms);
+        of_property_read_u32(pdev->dev.of_node, "wait-delay",
+                        &gpio_restart->wait_delay_ms);
+
+        platform_set_drvdata(pdev, gpio_restart);
+
+        ret = register_restart_handler(&gpio_restart->restart_handler);
+        if (ret) {
+                dev_err(&pdev->dev, "%s: cannot register restart handler, %d\n",
+                                __func__, ret);
+                return -ENODEV;
+        }
+
+        return 0;
+}
+
+static int gpio_restart_remove(struct platform_device *pdev)
+{
+        struct gpio_restart *gpio_restart = platform_get_drvdata(pdev);
+        int ret;
+
+        ret = unregister_restart_handler(&gpio_restart->restart_handler);
+        if (ret) {
+                dev_err(&pdev->dev,
+                                "%s: cannot unregister restart handler, %d\n",
+                                __func__, ret);
+                return -ENODEV;
+        }
+
+        return 0;
+}
+
+static const struct of_device_id of_gpio_restart_match[] = {
+        { .compatible = "gpio-restart", },
+        {},
+};
+
+static struct platform_driver gpio_restart_driver = {
+        .probe = gpio_restart_probe,
+        .remove = gpio_restart_remove,
+        .driver = {
+                .name = "restart-gpio",
+                .owner = THIS_MODULE,
+                .of_match_table = of_gpio_restart_match,
+        },
+};
+
+module_platform_driver(gpio_restart_driver);
+
+MODULE_AUTHOR("David Riley <davidriley@chromium.org>");
+MODULE_DESCRIPTION("GPIO restart driver");
+MODULE_LICENSE("GPL");