This driver registers a restart handler to set a GPIO line high/low
to reset a board based on devicetree bindings.
Signed-off-by: David Riley <davidri...@chromium.org>
---
.../devicetree/bindings/gpio/gpio-restart.txt | 48 +++++++
drivers/power/reset/Kconfig | 8 ++
drivers/power/reset/Makefile | 1 +
drivers/power/reset/gpio-restart.c | 142 +++++++++++++++++++++
4 files changed, 199 insertions(+)
create mode 100644 Documentation/devicetree/bindings/gpio/gpio-restart.txt
create mode 100644 drivers/power/reset/gpio-restart.c
diff --git a/Documentation/devicetree/bindings/gpio/gpio-restart.txt
b/Documentation/devicetree/bindings/gpio/gpio-restart.txt
new file mode 100644
index 0000000..7cd58788
--- /dev/null
+++ b/Documentation/devicetree/bindings/gpio/gpio-restart.txt
@@ -0,0 +1,48 @@
+Driver a GPIO line that can be used to restart the system as a
+restart handler.
+
+The driver supports both level triggered and edge triggered power off.
+At driver load time, the driver will request the given gpio line and
+install a restart handler. If the optional properties 'input' is
+not found, the GPIO line will be driven in the inactive state.
+Otherwise its configured as an input.
+
+When do_kernel_restart is called the various restart handlers will be tried
+in order. The gpio is configured as an output, and drive active, so
+triggering a level triggered power off condition. This will also cause an
+inactive->active edge condition, so triggering positive edge triggered
+power off. After a delay of 100ms, the GPIO is set to inactive, thus
+causing an active->inactive edge, triggering negative edge triggered power
+off. After another 100ms delay the GPIO is driver active again. If the
+power is still on and the CPU still running after a 3000ms delay, a
+WARN_ON(1) is emitted.
+
+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 power down the board set it to "Active Low", otherwise set
+ gpio to "Active High".
+
+Optional properties:
+- input : Initially configure the GPIO line as an input. Only reconfigure
+ it to an output when the machine_restart function is called. 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
+
+Examples:
+
+gpio-restart {
+ compatible = "gpio-restart";
+ gpios = <&gpio 4 0>;
+ priority = /bits/ 8 <200>;
+};
diff --git a/drivers/power/reset/Kconfig b/drivers/power/reset/Kconfig
index ca41523..f07e26c 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 a42e70e..199cb6e 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_QNAP) += qnap-poweroff.o
diff --git a/drivers/power/reset/gpio-restart.c
b/drivers/power/reset/gpio-restart.c
new file mode 100644
index 0000000..2cbff64
--- /dev/null
+++ b/drivers/power/reset/gpio-restart.c
@@ -0,0 +1,142 @@
+/*
+ * 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;
+};
+
+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);
+
+ BUG_ON(!gpio_restart->reset_gpio);
+
+ /* drive it active, also inactive->active edge */
+ gpiod_direction_output(gpio_restart->reset_gpio, 1);
+ mdelay(100);
+
+ /* drive inactive, also active->inactive edge */
+ gpiod_set_value(gpio_restart->reset_gpio, 0);
+ mdelay(100);
+
+ /* drive it active, also inactive->active edge */
+ gpiod_set_value(gpio_restart->reset_gpio, 1);
+
+ /* give it some time */
+ mdelay(3000);
+
+ WARN_ON(1);
+
+ return NOTIFY_DONE;
+}
+
+static int gpio_restart_probe(struct platform_device *pdev)
+{
+ struct gpio_restart *gpio_restart;
+ bool input = false;
+ u8 priority;
+ int ret;
+
+ gpio_restart = devm_kzalloc(&pdev->dev, sizeof(*gpio_restart),
+ GFP_KERNEL);
+ if (!gpio_restart)
+ return -ENOMEM;
+
+ gpio_restart->reset_gpio = devm_gpiod_get(&pdev->dev, NULL);
+ if (IS_ERR(gpio_restart->reset_gpio))
+ return PTR_ERR(gpio_restart->reset_gpio);
+
+ gpio_restart->restart_handler.notifier_call = gpio_restart_notify;
+ gpio_restart->restart_handler.priority = 128;
+
+ platform_set_drvdata(pdev, gpio_restart);
+
+ input = of_property_read_bool(pdev->dev.of_node, "input");
+ if (input) {
+ if (gpiod_direction_input(gpio_restart->reset_gpio)) {
+ dev_err(&pdev->dev,
+ "Could not set direction of reset GPIO to
input\n");
+ return -ENODEV;
+ }
+ } else {
+ if (gpiod_direction_output(gpio_restart->reset_gpio, 0)) {
+ dev_err(&pdev->dev,
+ "Could not set direction of reset GPIO\n");
+ return -ENODEV;
+ }
+ }
+
+ if (!of_property_read_u8(pdev->dev.of_node, "priority", &priority))
+ gpio_restart->restart_handler.priority = priority;
+
+ 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 <davidri...@chromium.org>");
+MODULE_DESCRIPTION("GPIO restart driver");
+MODULE_LICENSE("GPL");
--
2.0.0
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