Date:	Mon, 17 Jun 2013 08:40:31 +0200
From:	Johannes Thumshirn <johannes.thumshirn@....de>
To:	Guenter Roeck <linux@...ck-us.net>
CC:	Johannes Thumshirn <johannes.thumshirn@....de>, <wim@...ana.be>,
	<linux-kernel@...r.kernel.org>, <linux-watchdog@...r.kernel.org>,
	<guenter@...ck-us.net>
Subject: Re: [PATCH v9] watchdog: New watchdog driver for MEN A21 watchdogs

On Sun, Jun 16, 2013 at 03:07:15PM -0700, Guenter Roeck wrote:
> On Fri, Jun 14, 2013 at 12:58:37PM +0200, Johannes Thumshirn wrote:
> > This patch adds the driver for the watchdog devices found on MEN Mikro
> > Elektronik A21 VMEbus CPU Carrier Boards. It has DT-support and uses the
> > watchdog framework.
> >
> > Signed-off-by: Johannes Thumshirn <johannes.thumshirn@....de>
>
> Only nitpicks this time.
>

*g*

> > ---
> >
> >  Revision 2:
> >  * Removed unneeded open flag in struct a21_wdt_drv
> >  * Corrected 3bit reason code from gpio
> >  * Additional sysfs files are now part of watchdog sysfs
> >  * Changed OFF/ON delay in ping from 400ms to 10ns
> >  * Reworked timeout setting
> >  * Removed a21_wdt_ioctl(...)
> >
> >  Revision 3:
> >  * Changed pr_{err,info} to dev_{err,info}
> >  * Removed out of memory error print
> >  * Transition from "fast" to "slow" mode not allowed by chip
> >
> >  Revision 4:
> >  * Remove reboot_notifier and place disable code into platform_device's shutdown function
> >  * Removed sysfs interface
> >
> >  Revision 5:
> >  * Added setting of .bootstatus on driver init
> >  * Added initial timeout on driver init
> >
> >  Revision 6:
> >  * Use watchdog_init_timeout() to initialize timeout
> >
> >  Revision 7:
> >  * Fix possible get_bootstatus race condition
> >
> >  Revision 8:
> >  * a21_wdt_get_bootstatus() should return reset code
> >  * GPIOs are supplied via DT instead of being hardcoded. Code derived from
> >    (drivers/hwmon/gpio-fan.c)
> >  * Added Devicetree binding document
> >  * Driver now depends on GPIOLIB
> >
> >  Revision 9:
> >  * We need 6 GPIOs not only 1 to work
> >  * GPIO_WD_RST[0..2] are inputs
> >
> >  .../devicetree/bindings/gpio/men-a021-wdt.txt      |   25 ++
> >  MAINTAINERS                                        |    6 +
> >  drivers/watchdog/Kconfig                           |   12 +
> >  drivers/watchdog/Makefile                          |    1 +
> >  drivers/watchdog/mena21_wdt.c                      |  276 ++++++++++++++++++++
> >  5 files changed, 320 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/gpio/men-a021-wdt.txt
> >  create mode 100644 drivers/watchdog/mena21_wdt.c
> >
> > diff --git a/Documentation/devicetree/bindings/gpio/men-a021-wdt.txt b/Documentation/devicetree/bindings/gpio/men-a021-wdt.txt
> > new file mode 100644
> > index 0000000..370dee3
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/gpio/men-a021-wdt.txt
> > @@ -0,0 +1,25 @@
> > +Bindings for MEN A21 Watchdog device connected to GPIO lines
> > +
> > +Required properties:
> > +- compatible: "men,a021-wdt"
> > +- gpios: Specifies the pins that control the Watchdog, order:
> > +  1: Watchdog enable
> > +  2: Watchdog fast-mode
> > +  3: Watchdog trigger
> > +  4: Watchdog reset cause bit 0
> > +  5: Watchdog reset cause bit 1
> > +  6: Watchdog reset cause bit 2
> > +
> > +Optional properties:
> > +- None
> > +
> > +Example:
> > +	watchdog {
> > +		compatible ="men,a021-wdt";
> > +		gpios = <&gpio3 9  1	/* WD_EN */
> > +			 &gpio3 10 1	/* WD_FAST */
> > +			 &gpio3 11 1	/* WD_TRIG */
> > +			 &gpio3 6  1	/* RST_CAUSE[0] */
> > +			 &gpio3 7  1	/* RST_CAUSE[1] */
> > +			 &gpio3 8  1>;	/* RST_CAUSE[2] */
> > +	};
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index 5be702c..824261e 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -5317,6 +5317,12 @@ F:	drivers/mtd/
> >  F:	include/linux/mtd/
> >  F:	include/uapi/mtd/
> >
> > +MEN A21 WATCHDOG DRIVER
> > +M:  	Johannes Thumshirn <johannes.thumshirn@....de>
> > +L:	linux-watchdog@...r.kernel.org
> > +S:	Supported
> > +F:	drivers/watchdog/mena21_wdt.c
> > +
> >  METAG ARCHITECTURE
> >  M:	James Hogan <james.hogan@...tec.com>
> >  S:	Supported
> > diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> > index e89fc31..8b143ee 100644
> > --- a/drivers/watchdog/Kconfig
> > +++ b/drivers/watchdog/Kconfig
> > @@ -1172,6 +1172,18 @@ config BOOKE_WDT_DEFAULT_TIMEOUT
> >
> >  	  The value can be overridden by the wdt_period command-line parameter.
> >
> > +config MEN_A21_WDT
> > +       tristate "MEN A21 VME CPU Carrier Board Watchdog Timer"
> > +       select WATCHDOG_CORE
> > +       depends on GPIOLIB
> > +       help
> > +        Watchdog driver for MEN A21 VMEbus CPU Carrier Boards.
> > +
> > +	The driver can also be built as a module. If so, the module will be
> > +	called mena21_wdt.
> > +
> > +	If unsure select N here.
> > +
> >  # PPC64 Architecture
> >
> >  config WATCHDOG_RTAS
> > diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
> > index a300b94..bffdcb1 100644
> > --- a/drivers/watchdog/Makefile
> > +++ b/drivers/watchdog/Makefile
> > @@ -143,6 +143,7 @@ obj-$(CONFIG_8xxx_WDT) += mpc8xxx_wdt.o
> >  obj-$(CONFIG_MV64X60_WDT) += mv64x60_wdt.o
> >  obj-$(CONFIG_PIKA_WDT) += pika_wdt.o
> >  obj-$(CONFIG_BOOKE_WDT) += booke_wdt.o
> > +obj-$(CONFIG_MEN_A21_WDT) += mena21_wdt.o
> >
> >  # PPC64 Architecture
> >  obj-$(CONFIG_WATCHDOG_RTAS) += wdrtas.o
> > diff --git a/drivers/watchdog/mena21_wdt.c b/drivers/watchdog/mena21_wdt.c
> > new file mode 100644
> > index 0000000..0d3409a
> > --- /dev/null
> > +++ b/drivers/watchdog/mena21_wdt.c
> > @@ -0,0 +1,276 @@
> > +/*
> > + * Watchdog driver for the A21 VME CPU Boards
> > + *
> > + * Copyright (C) 2013 MEN Mikro Elektronik Nuernberg GmbH
> > + *
> > + * This program is free software; you can redistribute it and/or
> > + * modify it under the terms of the GNU General Public License
> > + * as published by the Free Software Foundation
> > + */
> > +#include <linux/module.h>
> > +#include <linux/moduleparam.h>
> > +#include <linux/types.h>
> > +#include <linux/kernel.h>
> > +#include <linux/slab.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/watchdog.h>
> > +#include <linux/uaccess.h>
> > +#include <linux/gpio.h>
> > +#include <linux/of_gpio.h>
> > +#include <linux/delay.h>
> > +#include <linux/bitops.h>
> > +
> > +#define NUM_GPIOS 6
> > +
> > +enum a21_wdt_gpios {
> > +	GPIO_WD_ENAB,
> > +	GPIO_WD_FAST,
> > +	GPIO_WD_TRIG,
> > +	GPIO_WD_RST0,
> > +	GPIO_WD_RST1,
> > +	GPIO_WD_RST2,
> > +};
> > +
> > +struct a21_wdt_drv {
> > +	struct watchdog_device wdt;
> > +	struct mutex lock;
> > +	unsigned gpios[NUM_GPIOS];
> > +};
> > +
> > +static bool nowayout = WATCHDOG_NOWAYOUT;
> > +module_param(nowayout, bool, 0);
> > +MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
> > +			    __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
> > +
> > +static unsigned int a21_wdt_get_bootstatus(struct a21_wdt_drv *drv)
> > +{
> > +	int reset = 0;
> > +
> > +	reset |= gpio_get_value(drv->gpios[GPIO_WD_RST0]) ? (1 << 0) : 0;
> > +	reset |= gpio_get_value(drv->gpios[GPIO_WD_RST1]) ? (1 << 1) : 0;
> > +	reset |= gpio_get_value(drv->gpios[GPIO_WD_RST2]) ? (1 << 2) : 0;
> > +
> > +	return reset;
> > +}
> > +
> > +static int a21_wdt_start(struct watchdog_device *wdt)
> > +{
> > +	struct a21_wdt_drv *drv = watchdog_get_drvdata(wdt);
> > +
> > +	mutex_lock(&drv->lock);
> > +
> > +	gpio_set_value(drv->gpios[GPIO_WD_ENAB], 1);
> > +
> > +	mutex_unlock(&drv->lock);
> > +
> > +	return 0;
> > +}
> > +
> > +static int a21_wdt_stop(struct watchdog_device *wdt)
> > +{
> > +	struct a21_wdt_drv *drv = watchdog_get_drvdata(wdt);
> > +
> > +	/* We don't stop if WDOG_NO_WAY_OUT is set */
> > +	if (test_bit(WDOG_NO_WAY_OUT, &wdt->status))
> > +		return -EINVAL;
> > +
> Already handled by watchdog core; no need to check again here.
>

ACK

> > +	mutex_lock(&drv->lock);
> > +
> > +	gpio_set_value(drv->gpios[GPIO_WD_ENAB], 0);
> > +
> > +	mutex_unlock(&drv->lock);
> > +
> > +	return 0;
> > +}
> > +
> > +static int a21_wdt_ping(struct watchdog_device *wdt)
> > +{
> > +	struct a21_wdt_drv *drv = watchdog_get_drvdata(wdt);
> > +
> > +	mutex_lock(&drv->lock);
> > +
> > +	gpio_set_value(drv->gpios[GPIO_WD_TRIG], 0);
> > +	ndelay(10);
>
> Is the delay specified somewehere or just to be sure ?
>

I tried to meter it out. 10ns seemed to be a good value where the reset is still
reliable. Making it smaller can make it a bit unreliable. Also it is roughly
10*CPLD clock, which seems like a good value to me.

> > +	gpio_set_value(drv->gpios[GPIO_WD_TRIG], 1);
> > +
> > +	mutex_unlock(&drv->lock);
> > +
> > +	return 0;
> > +}
> > +
> > +static int a21_wdt_set_timeout(struct watchdog_device *wdt,
> > +			       unsigned int timeout)
> > +{
> > +	struct a21_wdt_drv *drv = watchdog_get_drvdata(wdt);
> > +
> > +	if (timeout != 1 && timeout != 30) {
> > +		dev_err(wdt->dev, "Only 1 and 30 allowed as timeout\n");
> > +		return -EINVAL;
> > +	}
> > +
> > +	if (timeout == 30 && wdt->timeout == 1) {
> > +		dev_err(wdt->dev,
> > +			"Transition from fast to slow mode not allowed\n");
> > +		return -EINVAL;
> > +	}
> > +
> > +	mutex_lock(&drv->lock);
> > +
> > +	if (timeout == 1)
> > +		gpio_set_value(drv->gpios[GPIO_WD_FAST], 1);
> > +	else
> > +		gpio_set_value(drv->gpios[GPIO_WD_FAST], 0);
> > +
> > +	wdt->timeout = timeout;
> > +
> > +	mutex_unlock(&drv->lock);
> > +
> > +	return 0;
> > +}
> > +
> > +static const struct watchdog_info a21_wdt_info = {
> > +	.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
> > +	.identity = "MEN A21 Watchdog",
> > +};
> > +
> > +static const struct watchdog_ops a21_wdt_ops = {
> > +	.owner = THIS_MODULE,
> > +	.start = a21_wdt_start,
> > +	.stop = a21_wdt_stop,
> > +	.ping = a21_wdt_ping,
> > +	.set_timeout = a21_wdt_set_timeout,
> > +};
> > +
> > +static struct watchdog_device a21_wdt = {
> > +	.info = &a21_wdt_info,
> > +	.ops = &a21_wdt_ops,
> > +	.min_timeout = 1,
> > +	.max_timeout = 30,
> > +};
> > +
> > +static int a21_wdt_probe(struct platform_device *pdev)
> > +{
> > +	struct device_node *node;
> > +	struct a21_wdt_drv *drv;
> > +	unsigned int reset = 0;
> > +	int num_gpios;
> > +	int ret;
> > +	int i;
> > +
> > +	dev_info(&pdev->dev, "MEN A21 watchdog timer driver enabled\n");
> > +
> Move to the very end of this function; otherwise it is misleading if lading the
> driver fails.
>

OK.

> > +	drv = devm_kzalloc(&pdev->dev, sizeof(struct a21_wdt_drv), GFP_KERNEL);
> > +	if (!drv)
> > +		return -ENOMEM;
> > +
> > +	/* Fill GPIO pin array */
> > +	node = pdev->dev.of_node;
> > +
> > +	num_gpios = of_gpio_count(node);
> > +	if (num_gpios != NUM_GPIOS) {
> > +		dev_err(&pdev->dev, "gpios DT property wrong, got %d want %d",
> > +			num_gpios, NUM_GPIOS);
> > +		return -ENODEV;
> > +	}
> > +
> > +	for (i = 0; i < num_gpios; i++) {
> > +		int val;
> > +
> > +		val = of_get_gpio(node, i);
> > +		if (val < 0)
> > +			return val;
> > +
> > +		drv->gpios[i] = val;
> > +	}
> > +
> > +	/* Request the used GPIOs */
> > +	for (i = 0; i < num_gpios; i++) {
> > +		ret = devm_gpio_request(&pdev->dev, drv->gpios[i],
> > +					"MEN A21 Watchdog");
> > +		if (ret)
> > +			return ret;
> > +
> > +		if (i < GPIO_WD_RST0)
> > +			ret = gpio_direction_output(drv->gpios[i],
> > +						gpio_get_value(drv->gpios[i]));
> > +		else		/* GPIO_WD_RST[0..2] are inputs */
> > +			ret = gpio_direction_input(drv->gpios[i]);
> > +		if (ret)
> > +			return ret;
> > +	}
> > +
> > +	mutex_init(&drv->lock);
> > +	watchdog_init_timeout(&a21_wdt, 30, &pdev->dev);
> > +	watchdog_set_nowayout(&a21_wdt, nowayout);
> > +	watchdog_set_drvdata(&a21_wdt, drv);
> > +
> > +	reset = a21_wdt_get_bootstatus(drv);
> > +	if (reset == 2)
> > +		a21_wdt.bootstatus |= WDIOF_EXTERN1;
> > +	else if (reset == 4)
> > +		a21_wdt.bootstatus |= WDIOF_CARDRESET;
> > +	else if (reset == 5)
> > +		a21_wdt.bootstatus |= WDIOF_POWERUNDER;
> > +	else if (reset == 7)
> > +		a21_wdt.bootstatus |= WDIOF_EXTERN2;
> > +
> > +
> One empty line is sufficient.
>
Args. Yep.
> > +	ret = watchdog_register_device(&a21_wdt);
> > +	if (ret) {
> > +		dev_err(&pdev->dev, "Cannot register watchdog device\n");
> > +		goto err_register_wd;
> > +	}
> > +
> > +	dev_set_drvdata(&pdev->dev, drv);
> > +
> > +	return 0;
> > +
> > +err_register_wd:
> > +	mutex_destroy(&drv->lock);
> > +
> > +	return ret;
> > +}
> > +
> > +static int a21_wdt_remove(struct platform_device *pdev)
> > +{
> > +	struct a21_wdt_drv *drv = dev_get_drvdata(&pdev->dev);
> > +
> > +	dev_warn(&pdev->dev,
> > +		"Unregistering A21 watchdog driver, board may reboot\n");
> > +
> > +
> One empty line
>
^^
> > +	watchdog_unregister_device(&drv->wdt);
> > +
> > +	mutex_destroy(&drv->lock);
> > +
> > +	return 0;
> > +}
> > +
> > +static void a21_wdt_shutdown(struct platform_device *pdev)
> > +{
> > +	struct a21_wdt_drv *drv = dev_get_drvdata(&pdev->dev);
> > +
> > +	gpio_set_value(drv->gpios[GPIO_WD_ENAB], 0);
> > +}
> > +
> > +static const struct of_device_id a21_wdt_ids[] = {
> > +	{ .compatible = "men,a021-wdt" },
> > +	{ },
> > +};
> > +
> > +static struct platform_driver a21_wdt_driver = {
> > +	.probe = a21_wdt_probe,
> > +	.remove = a21_wdt_remove,
> > +	.shutdown = a21_wdt_shutdown,
> > +	.driver = {
> > +		.name = "a21-watchdog",
> > +		.of_match_table = a21_wdt_ids,
> > +	},
> > +};
> > +
> > +module_platform_driver(a21_wdt_driver);
> > +
> > +MODULE_AUTHOR("MEN Mikro Elektronik");
> > +MODULE_DESCRIPTION("MEN A21 Watchdog");
> > +MODULE_LICENSE("GPL");
> > +MODULE_ALIAS("platform:a21-watchdog");
> > --
> > 1.7.9.5
> >
> > --
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> >
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