Message-ID: <20110212094229.GH17755@angua.secretlab.ca>
Date:	Sat, 12 Feb 2011 02:42:29 -0700
From:	Grant Likely <grant.likely@...retlab.ca>
To:	Tobias Klauser <tklauser@...tanz.ch>
Cc:	Wim Van Sebroeck <wim@...ana.be>, linux-watchdog@...r.kernel.org,
	Jamie Iles <jamie@...ieiles.com>,
	Walter Goossens <waltergoossens@...e.nl>,
	devicetree-discuss@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	nios2-dev@...c.et.ntust.edu.tw
Subject: Re: [PATCH v3] watchdog: Add driver for Altera Watchdog Timer

On Wed, Feb 09, 2011 at 08:19:12AM +0100, Tobias Klauser wrote:
> This driver adds support for the Altera Timer in the Watchdog Timer
> configuration. This component is usually found on SOPC (System on
> Programmable Chip) for Altera FPGAs.
> 
> Signed-off-by: Tobias Klauser <tklauser@...tanz.ch>
> Reviewed-by: Jamie Iles <jamie@...ieiles.com>

Acked-by: Grant Likely <grant.likely@...retlab.ca> for the devicetree binding.

g.

> ---
> Thanks a lot to Jamie Iles and Walter Goossens for their feedback on v2.
> 
> changes for v3:
>  - Make altera_wdt_setup static void (as suggested by Jamie)
>  - Use const __be32 * for devicetree properties (as suggested by Walter)
> changes for v2:
>  - Get driver properties from devicetree (and document them), thus the
>    driver depends on OF
>  - Do not select WATCHDOG_NOWAYOUT, but instead implement a software
>    timer resetting the watchdog timer when the device is not open
>  - Only support a single instance of the watchdog, so the private data
>    can be kept in static data
>  - Use devm_* functions in altera_wdt_probe to simplify cleanup and
>    error handling
>  - Remove empty altera_wdt_shutdown function
>  - Add MODULE_LICENSE (GPL)
> 
> 
>  .../devicetree/bindings/watchdog/altera_wdt.txt    |    7 +
>  drivers/watchdog/Kconfig                           |    8 +
>  drivers/watchdog/Makefile                          |    1 +
>  drivers/watchdog/altera_wdt.c                      |  309 ++++++++++++++++++++
>  4 files changed, 325 insertions(+), 0 deletions(-)
>  create mode 100644 Documentation/devicetree/bindings/watchdog/altera_wdt.txt
>  create mode 100644 drivers/watchdog/altera_wdt.c
> 
> diff --git a/Documentation/devicetree/bindings/watchdog/altera_wdt.txt b/Documentation/devicetree/bindings/watchdog/altera_wdt.txt
> new file mode 100644
> index 0000000..16ac949
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/watchdog/altera_wdt.txt
> @@ -0,0 +1,7 @@
> +Altera Watchdog Timer
> +
> +Required properties:
> +- compatible : should be "ALTR,wdt-1.0"
> +- clock-frequency : frequency of the clock input
> +- timeout : load value of the timer (number of clock ticks until watchdog
> +            resets)
> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> index bd6a33d..ebcafb0 100644
> --- a/drivers/watchdog/Kconfig
> +++ b/drivers/watchdog/Kconfig
> @@ -69,6 +69,14 @@ config WM8350_WATCHDOG
>  	  Support for the watchdog in the WM8350 AudioPlus PMIC.  When
>  	  the watchdog triggers the system will be reset.
>  
> +config ALTERA_WDT
> +	tristate "Altera Watchdog Timer"
> +	depends on OF
> +	help
> +	  Support for the Altera Timer in the Watchdog Timer configuration. This
> +	  component is found on SOPC (System on Programmable Chip) for Altera
> +	  FPGAs.
> +
>  # ALPHA Architecture
>  
>  # ARM Architecture
> diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
> index fd9c8c0..48a2167 100644
> --- a/drivers/watchdog/Makefile
> +++ b/drivers/watchdog/Makefile
> @@ -153,4 +153,5 @@ obj-$(CONFIG_WATCHDOG_CP1XXX)		+= cpwd.o
>  obj-$(CONFIG_WM831X_WATCHDOG) += wm831x_wdt.o
>  obj-$(CONFIG_WM8350_WATCHDOG) += wm8350_wdt.o
>  obj-$(CONFIG_MAX63XX_WATCHDOG) += max63xx_wdt.o
> +obj-$(CONFIG_ALTERA_WDT) += altera_wdt.o
>  obj-$(CONFIG_SOFT_WATCHDOG) += softdog.o
> diff --git a/drivers/watchdog/altera_wdt.c b/drivers/watchdog/altera_wdt.c
> new file mode 100644
> index 0000000..2a7f14a
> --- /dev/null
> +++ b/drivers/watchdog/altera_wdt.c
> @@ -0,0 +1,309 @@
> +/*
> + * Driver for the Altera Watchdog Timer
> + *
> + * Copyright (C) 2011 Tobias Klauser <tklauser@...tanz.ch>
> + * Copyright (C) 2005 Walter Goossens
> + *
> + * Originally based on wdt.c which is
> + *
> + * Copyright (C) 1995-1997 Alan Cox <alan@...rguk.ukuu.org.uk>
> + *
> + * Software timeout heartbeat code based on pika_wdt.c which is
> + *
> + * Copyright (c) 2008 PIKA Technologies
> + *
> + * 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; either version 2 of the License, or
> + * (at your option) any later version.
> + */
> +
> +#include <linux/module.h>
> +#include <linux/kernel.h>
> +#include <linux/miscdevice.h>
> +#include <linux/watchdog.h>
> +#include <linux/platform_device.h>
> +#include <linux/fs.h>
> +#include <linux/init.h>
> +#include <linux/jiffies.h>
> +#include <linux/timer.h>
> +#include <linux/io.h>
> +#include <linux/uaccess.h>
> +#include <linux/of_platform.h>
> +
> +#define WATCHDOG_NAME	"altera_wdt"
> +
> +/* Register offsets */
> +#define ALTERA_WDT_STATUS	0x00
> +#define ALTERA_WDT_CONTROL	0x04
> +#define ALTERA_WDT_PERIODL	0x08
> +#define ALTERA_WDT_PERIODH	0x0C
> +
> +#define ALTERA_WDT_RUN_BIT	0x04
> +
> +/* User land timeout */
> +#define WDT_HEARTBEAT 15
> +static int heartbeat = WDT_HEARTBEAT;
> +module_param(heartbeat, int, 0);
> +MODULE_PARM_DESC(heartbeat, "Watchdog heartbeats in seconds. "
> +	"(default = " __MODULE_STRING(WDT_HEARTBEAT) ")");
> +
> +static int nowayout = WATCHDOG_NOWAYOUT;
> +module_param(nowayout, int, 0);
> +MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started "
> +	"(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
> +
> +static struct {
> +	void __iomem *base;
> +	unsigned long wdt_timeout;	/* timeout of the hardware timer */
> +
> +	unsigned long next_heartbeat;	/* the next_heartbeat for the timer */
> +	unsigned long is_open;
> +	char expect_close;
> +	struct timer_list timer;	/* software timer that pings the watchdog */
> +} altera_wdt_priv;
> +
> +/*
> + * Start the watchdog. Once it has been started, it cannot be stopped anymore.
> + */
> +static void altera_wdt_setup(void)
> +{
> +	u32 control = readl(altera_wdt_priv.base + ALTERA_WDT_CONTROL);
> +
> +	writel(control | ALTERA_WDT_RUN_BIT, altera_wdt_priv.base + ALTERA_WDT_CONTROL);
> +}
> +
> +/*
> + * Tickle the watchdog (reset the watchdog timer)
> + */
> +static void altera_wdt_reset(void)
> +{
> +	/* It doesn't matter what value we write */
> +	writel(1, altera_wdt_priv.base + ALTERA_WDT_PERIODL);
> +}
> +
> +/*
> + * Software timer tick
> + */
> +static void altera_wdt_ping(unsigned long data)
> +{
> +	if (time_before(jiffies, altera_wdt_priv.next_heartbeat) ||
> +			(!nowayout && !altera_wdt_priv.is_open)) {
> +		altera_wdt_reset();
> +		mod_timer(&altera_wdt_priv.timer, jiffies + altera_wdt_priv.wdt_timeout);
> +	} else
> +		pr_crit(WATCHDOG_NAME ": I will reset your machine!\n");
> +}
> +
> +static void altera_wdt_keepalive(void)
> +{
> +	altera_wdt_priv.next_heartbeat = jiffies + heartbeat * HZ;
> +}
> +
> +static void altera_wdt_start(void)
> +{
> +	altera_wdt_keepalive();
> +	mod_timer(&altera_wdt_priv.timer, jiffies + altera_wdt_priv.wdt_timeout);
> +}
> +
> +static int altera_wdt_open(struct inode *inode, struct file *file)
> +{
> +	/* /dev/watchdog can only be opened once */
> +	if (test_and_set_bit(0, &altera_wdt_priv.is_open))
> +		return -EBUSY;
> +
> +	altera_wdt_start();
> +
> +	return nonseekable_open(inode, file);
> +}
> +
> +static int altera_wdt_release(struct inode *inode, struct file *file)
> +{
> +	/* stop internal ping */
> +	if (!altera_wdt_priv.expect_close)
> +		del_timer(&altera_wdt_priv.timer);
> +
> +	clear_bit(0, &altera_wdt_priv.is_open);
> +	altera_wdt_priv.expect_close = 0;
> +
> +	return 0;
> +}
> +
> +static ssize_t altera_wdt_write(struct file *file, const char __user *data,
> +		size_t len, loff_t *ppos)
> +{
> +	if (!len)
> +		return 0;
> +
> +	/* Scan for magic character */
> +	if (!nowayout) {
> +		size_t i;
> +
> +		altera_wdt_priv.expect_close = 0;
> +
> +		for (i = 0; i < len; i++) {
> +			char c;
> +			if (get_user(c, data + i))
> +				return -EFAULT;
> +			if (c == 'V') {
> +				altera_wdt_priv.expect_close = 42;
> +				break;
> +			}
> +		}
> +	}
> +
> +	altera_wdt_keepalive();
> +
> +	return len;
> +}
> +
> +static const struct watchdog_info altera_wdt_info = {
> +	.identity		= "Altera Watchdog",
> +	.options		= WDIOF_SETTIMEOUT |
> +				  WDIOF_KEEPALIVEPING |
> +				  WDIOF_MAGICCLOSE,
> +	.firmware_version	= 1,
> +};
> +
> +static long altera_wdt_ioctl(struct file *file, unsigned int cmd,
> +		unsigned long arg)
> +{
> +	void __user *argp = (void __user *) arg;
> +	int __user *p = argp;
> +	int new_value;
> +
> +	switch (cmd) {
> +	case WDIOC_GETSUPPORT:
> +		return copy_to_user(argp, &altera_wdt_info, sizeof(altera_wdt_info));
> +
> +	case WDIOC_GETSTATUS:
> +	case WDIOC_GETBOOTSTATUS:
> +		return put_user(0, p);
> +
> +	case WDIOC_KEEPALIVE:
> +		altera_wdt_keepalive();
> +		return 0;
> +
> +	case WDIOC_SETTIMEOUT:
> +		if (get_user(new_value, p))
> +			return -EFAULT;
> +
> +		heartbeat = new_value;
> +		altera_wdt_keepalive();
> +
> +		return put_user(new_value, p);  /* return current value */
> +
> +	case WDIOC_GETTIMEOUT:
> +		return put_user(heartbeat, p);
> +
> +	default:
> +		return -ENOTTY;
> +	}
> +}
> +
> +static const struct file_operations altera_wdt_fops = {
> +	.owner		= THIS_MODULE,
> +	.llseek		= no_llseek,
> +	.open		= altera_wdt_open,
> +	.release	= altera_wdt_release,
> +	.write		= altera_wdt_write,
> +	.unlocked_ioctl	= altera_wdt_ioctl,
> +};
> +
> +static struct miscdevice altera_wdt_miscdev = {
> +	.minor	= WATCHDOG_MINOR,
> +	.name	= "watchdog",
> +	.fops	= &altera_wdt_fops,
> +};
> +
> +static int __devinit altera_wdt_probe(struct platform_device *pdev)
> +{
> +	struct resource *res, *mem;
> +	const __be32 *freq_prop, *timeout_prop;
> +	unsigned long timeout;
> +	int ret;
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	if (!res)
> +		return -ENOENT;
> +
> +	mem = devm_request_mem_region(&pdev->dev, res->start,
> +				      resource_size(res), pdev->name);
> +	if (!mem)
> +		return -EBUSY;
> +
> +	altera_wdt_priv.base = devm_ioremap_nocache(&pdev->dev, mem->start,
> +						    resource_size(mem));
> +	if (!altera_wdt_priv.base)
> +		return -ENOMEM;
> +
> +	freq_prop = of_get_property(pdev->dev.of_node, "clock-frequency", NULL);
> +	if (!freq_prop)
> +		return -ENODEV;
> +
> +	timeout_prop = of_get_property(pdev->dev.of_node, "timeout", NULL);
> +	if (!timeout_prop)
> +		return -ENODEV;
> +
> +	/* Add 1 as the timeout property actually holds the load value */
> +	timeout = be32_to_cpup(timeout_prop) + 1;
> +	/* Convert timeout to msecs */
> +	timeout = timeout / (be32_to_cpup(freq_prop) / MSEC_PER_SEC);
> +	/* Tickle the watchdog twice per timeout period */
> +	altera_wdt_priv.wdt_timeout = msecs_to_jiffies(timeout / 2);
> +
> +	ret = misc_register(&altera_wdt_miscdev);
> +	if (ret)
> +		return ret;
> +
> +	altera_wdt_setup();
> +	altera_wdt_priv.next_heartbeat = jiffies + heartbeat * HZ;
> +	setup_timer(&altera_wdt_priv.timer, altera_wdt_ping, 0);
> +	mod_timer(&altera_wdt_priv.timer, jiffies + altera_wdt_priv.wdt_timeout);
> +
> +	pr_info(WATCHDOG_NAME " enabled (heartbeat=%d sec, nowayout=%d)\n",
> +		heartbeat, nowayout);
> +
> +	return 0;
> +}
> +
> +static int __devexit altera_wdt_remove(struct platform_device *pdev)
> +{
> +	misc_deregister(&altera_wdt_miscdev);
> +	return 0;
> +}
> +
> +static struct of_device_id altera_wdt_match[] = {
> +	{ .compatible = "altr,wdt-1.0", },
> +	{},
> +};
> +MODULE_DEVICE_TABLE(of, altera_wdt_match);
> +
> +static struct platform_driver altera_wdt_driver = {
> +	.probe		= altera_wdt_probe,
> +	.remove		= __devexit_p(altera_wdt_remove),
> +	.driver		= {
> +		.owner		= THIS_MODULE,
> +		.name		= WATCHDOG_NAME,
> +		.of_match_table	= altera_wdt_match,
> +	},
> +};
> +
> +static int __init altera_wdt_init(void)
> +{
> +	return platform_driver_register(&altera_wdt_driver);
> +}
> +
> +static void __exit altera_wdt_exit(void)
> +{
> +	platform_driver_unregister(&altera_wdt_driver);
> +}
> +
> +module_init(altera_wdt_init);
> +module_exit(altera_wdt_exit);
> +
> +MODULE_AUTHOR("Walter Goossens, Tobias Klauser <tklauser@...tanz.ch>");
> +MODULE_DESCRIPTION("Driver for Altera Watchdog Timer");
> +MODULE_LICENSE("GPL");
> +MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
> +MODULE_ALIAS("platform:" WATCHDOG_NAME);
> -- 
> 1.7.0.4
> 
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