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Date: Tue, 26 Aug 2014 19:40:47 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: David Riley <davidriley@...omium.org>,
Sebastian Reichel <sre@...nel.org>,
Dmitry Eremin-Solenikov <dbaryshkov@...il.com>,
David Woodhouse <dwmw2@...radead.org>
CC: Rob Herring <robh+dt@...nel.org>, Pawel Moll <pawel.moll@....com>,
Mark Rutland <mark.rutland@....com>,
Ian Campbell <ijc+devicetree@...lion.org.uk>,
Kumar Gala <galak@...eaurora.org>,
Grant Likely <grant.likely@...aro.org>,
Arnd Bergmann <arnd@...db.de>,
Anton Vorontsov <anton@...msg.org>,
Marc Carino <marc.ceeeee@...il.com>,
Anders Berg <anders.berg@....com>,
Laxman Dewangan <ldewangan@...dia.com>,
Ivan Khoronzhuk <ivan.khoronzhuk@...com>,
Maxime Ripard <maxime.ripard@...e-electrons.com>,
Haojian Zhuang <haojian.zhuang@...aro.org>,
Jamie Lentin <jm@...tin.co.uk>,
Doug Anderson <dianders@...omium.org>,
devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-pm@...r.kernel.org
Subject: Re: [PATCH v1 1/1] power: Add simple gpio-restart driver
On 08/26/2014 04:45 PM, David Riley wrote:
> 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 <davidriley@...omium.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.
Maybe describe this as open source ?
> +- 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);
> +
Is this really necessary ? First, it can't really happen,
but if it happens anyway I am not sure if there might be
a possibility for recursiveness. After all, this is called
from machine_restart().
> + /* 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);
> +
Should those delays be parameters ?
> + 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);
> +
There is now a flags parameter to devm_gpiod_get which should help
handling input/output with a single call.
> + 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 <davidriley@...omium.org>");
> +MODULE_DESCRIPTION("GPIO restart driver");
> +MODULE_LICENSE("GPL");
>
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