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Date: Wed, 27 Aug 2014 11:02:45 -0700
From: David Riley <davidriley@...gle.com>
To: Guenter Roeck <linux@...ck-us.net>
Cc: Sebastian Reichel <sre@...nel.org>,
Dmitry Eremin-Solenikov <dbaryshkov@...il.com>,
David Woodhouse <dwmw2@...radead.org>,
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" <devicetree@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>
Subject: Re: [PATCH v1 1/1] power: Add simple gpio-restart driver
On Tue, Aug 26, 2014 at 7:40 PM, Guenter Roeck <linux@...ck-us.net> wrote:
> 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 ?
Done.
>> +- 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().
I've removed it.
>> + /* 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 ?
Done.
>
>
>> + 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.
Done.
>
>> + 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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