--- /dev/null
+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>;
+};
--- /dev/null
+/*
+ * 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");
git.openpandora.org / pandora-kernel.git / commitdiff