Re: [PATCH v2 2/2] watchdog: add support for Sigma Designs SMP86xx/SMP87xx

[Guenter Roeck <linux@roeck-us.net>]

On 11/18/2015 09:55 AM, Mans Rullgard wrote:
> This adds support for the Sigma Designs SMP86xx/SMP87xx family built-in
> watchdog.
>
> Signed-off-by: Mans Rullgard <mans@mansr.com>
> ---
> Changes:
> - combine start and ping functions
> - use watchdog_init_timeout()
> - calculate max timeout from clock rate
> - add get_timeleft callback
> - check if already running on startup
> - add explanatory comments
> - improve kconfig text
> ---
>   drivers/watchdog/Kconfig      |  10 ++
>   drivers/watchdog/Makefile     |   1 +
>   drivers/watchdog/tangox_wdt.c | 213 ++++++++++++++++++++++++++++++++++++++++++
>   3 files changed, 224 insertions(+)
>   create mode 100644 drivers/watchdog/tangox_wdt.c
>
> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> index 7a8a6c6..f43ff7a 100644
> --- a/drivers/watchdog/Kconfig
> +++ b/drivers/watchdog/Kconfig
> @@ -135,6 +135,16 @@ config MENF21BMC_WATCHDOG
>   	  This driver can also be built as a module. If so the module
>   	  will be called menf21bmc_wdt.
>
> +config TANGOX_WATCHDOG
> +	tristate "Sigma Designs SMP86xx/SMP87xx watchdog"
> +	select WATCHDOG_CORE
> +	depends on ARCH_TANGOX || COMPILE_TEST
> +	help
> +	  Support for the watchdog in Sigma Designs SMP86xx (tango3)
> +	  and SMP87xx (tango4) family chips.
> +
> +	  This driver can be built as a module. The module name is tangox_wdt.
> +
>   config WM831X_WATCHDOG
>   	tristate "WM831x watchdog"
>   	depends on MFD_WM831X
> diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
> index 53d4827..46cb387 100644
> --- a/drivers/watchdog/Makefile
> +++ b/drivers/watchdog/Makefile
> @@ -187,6 +187,7 @@ obj-$(CONFIG_DA9055_WATCHDOG) += da9055_wdt.o
>   obj-$(CONFIG_DA9062_WATCHDOG) += da9062_wdt.o
>   obj-$(CONFIG_DA9063_WATCHDOG) += da9063_wdt.o
>   obj-$(CONFIG_GPIO_WATCHDOG)	+= gpio_wdt.o
> +obj-$(CONFIG_TANGOX_WATCHDOG) += tangox_wdt.o
>   obj-$(CONFIG_WM831X_WATCHDOG) += wm831x_wdt.o
>   obj-$(CONFIG_WM8350_WATCHDOG) += wm8350_wdt.o
>   obj-$(CONFIG_MAX63XX_WATCHDOG) += max63xx_wdt.o
> diff --git a/drivers/watchdog/tangox_wdt.c b/drivers/watchdog/tangox_wdt.c
> new file mode 100644
> index 0000000..0b458ff
> --- /dev/null
> +++ b/drivers/watchdog/tangox_wdt.c
> @@ -0,0 +1,213 @@
> +/*
> + *  Copyright (C) 2015 Mans Rullgard <mans@mansr.com>
> + *  SMP86xx/SMP87xx Watchdog driver
> + *
> + *  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/clk.h>
> +#include <linux/delay.h>
> +#include <linux/io.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/moduleparam.h>
> +#include <linux/notifier.h>
> +#include <linux/platform_device.h>
> +#include <linux/reboot.h>
> +#include <linux/watchdog.h>
> +
> +#define DEFAULT_TIMEOUT 30
> +
> +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 timeout;
> +module_param(timeout, int, 0);
> +MODULE_PARM_DESC(timeout, "Watchdog timeout");
> +
> +/*
> + * Counter counts down from programmed value.  Reset asserts when
> + * the counter reaches 1.
> + */
> +#define WD_COUNTER		0
> +
> +#define WD_CONFIG		4
> +#define WD_CONFIG_XTAL_IN	BIT(0)
> +#define WD_CONFIG_DISABLE	BIT(31)
> +

Please include linux/bitops.h when using BIT macros.

> +struct tangox_wdt_device {
> +	struct watchdog_device wdt;
> +	void __iomem *base;
> +	unsigned long clk_rate;
> +	struct clk *clk;
> +	struct notifier_block restart;
> +};
> +
> +static int tangox_wdt_set_timeout(struct watchdog_device *wdt,
> +				  unsigned int new_timeout)
> +{
> +	wdt->timeout = new_timeout;
> +
> +	return 0;
> +}
> +
> +static int tangox_wdt_start(struct watchdog_device *wdt)
> +{
> +	struct tangox_wdt_device *dev = watchdog_get_drvdata(wdt);
> +	u32 ticks;
> +
> +	ticks = 1 + wdt->timeout * dev->clk_rate;
> +	writel(ticks, dev->base + WD_COUNTER);
> +
> +	return 0;
> +}
> +
> +static int tangox_wdt_stop(struct watchdog_device *wdt)
> +{
> +	struct tangox_wdt_device *dev = watchdog_get_drvdata(wdt);
> +
> +	writel(0, dev->base + WD_COUNTER);
> +
> +	return 0;
> +}
> +
> +static unsigned int tangox_wdt_get_timeleft(struct watchdog_device *wdt)
> +{
> +	struct tangox_wdt_device *dev = watchdog_get_drvdata(wdt);
> +	u32 count;
> +
> +	count = readl(dev->base + WD_COUNTER);
> +
> +	if (!count)
> +		return 0;
> +
> +	return (count - 1) / dev->clk_rate;
> +}
> +
> +static const struct watchdog_info tangox_wdt_info = {
> +	.options  = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
> +	.identity = "tangox watchdog",
> +};
> +
> +static const struct watchdog_ops tangox_wdt_ops = {
> +	.start		= tangox_wdt_start,
> +	.stop		= tangox_wdt_stop,
> +	.set_timeout	= tangox_wdt_set_timeout,
> +	.get_timeleft	= tangox_wdt_get_timeleft,
> +};
> +
> +static int tangox_wdt_restart(struct notifier_block *nb, unsigned long action,
> +			      void *data)
> +{
> +	struct tangox_wdt_device *dev =
> +		container_of(nb, struct tangox_wdt_device, restart);
> +
> +	writel(1, dev->base + WD_COUNTER);
> +
> +	return NOTIFY_DONE;
> +}
> +
> +static int tangox_wdt_probe(struct platform_device *pdev)
> +{
> +	struct tangox_wdt_device *dev;
> +	struct resource *res;
> +	int err;
> +
> +	dev = devm_kzalloc(&pdev->dev, sizeof(*dev), GFP_KERNEL);
> +	if (!dev)
> +		return -ENOMEM;
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	dev->base = devm_ioremap_resource(&pdev->dev, res);
> +	if (IS_ERR(dev->base))
> +		return PTR_ERR(dev->base);
> +
> +	dev->clk = devm_clk_get(&pdev->dev, NULL);
> +	if (IS_ERR(dev->clk))
> +		return PTR_ERR(dev->clk);
> +
> +	err = clk_prepare_enable(dev->clk);
> +	if (err)
> +		return err;
> +
> +	dev->clk_rate = clk_get_rate(dev->clk);
> +
> +	dev->wdt.parent = &pdev->dev;
> +	dev->wdt.info = &tangox_wdt_info;
> +	dev->wdt.ops = &tangox_wdt_ops;
> +	dev->wdt.timeout = DEFAULT_TIMEOUT;
> +	dev->wdt.min_timeout = 1;
> +	dev->wdt.max_timeout = (U32_MAX - 1) / dev->clk_rate;
> +
> +	watchdog_init_timeout(&dev->wdt, timeout, &pdev->dev);
> +	watchdog_set_nowayout(&dev->wdt, nowayout);
> +	watchdog_set_drvdata(&dev->wdt, dev);
> +
> +	writel(WD_CONFIG_XTAL_IN, dev->base + WD_CONFIG);

What happens if the DISABLE bit was previously set (assuming
that DISABLE means that the watchdog is disabled) ?

Concern I guess would be the combination of DISABLE being set
and WD_COUNTER at a value != 0 (say, 1). That might effectively
auto-enable the watchdog or even reset the system.

> +
> +	/*
> +	 * Mark as active and restart with configured timeout if
> +	 * already running.
> +	 */
> +	if (readl(dev->base + WD_COUNTER)) {
> +		set_bit(WDOG_ACTIVE, &dev->wdt.status);
> +		tangox_wdt_start(&dev->wdt);
> +	}
> +
> +	err = watchdog_register_device(&dev->wdt);
> +	if (err)
> +		return err;

Needs clk_disable_unprepare().

> +
> +	platform_set_drvdata(pdev, dev);
> +
> +	dev->restart.notifier_call = tangox_wdt_restart;
> +	dev->restart.priority = 128;
> +	err = register_restart_handler(&dev->restart);
> +	if (err)
> +		dev_warn(&pdev->dev, "failed to register restart handler\n");
> +
> +	dev_info(dev->wdt.dev, "SMP86xx/SMP87xx watchdog registered\n");
> +
> +	return 0;
> +}
> +
> +static int tangox_wdt_remove(struct platform_device *pdev)
> +{
> +	struct tangox_wdt_device *dev = platform_get_drvdata(pdev);
> +
> +	tangox_wdt_stop(&dev->wdt);
> +	clk_disable_unprepare(dev->clk);
> +
> +	unregister_restart_handler(&dev->restart);
> +	watchdog_unregister_device(&dev->wdt);
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id tangox_wdt_dt_ids[] = {
> +	{ .compatible = "sigma,smp8642-wdt" },
> +	{ .compatible = "sigma,smp8759-wdt" },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(of, tangox_wdt_dt_ids);
> +
> +static struct platform_driver tangox_wdt_driver = {
> +	.probe	= tangox_wdt_probe,
> +	.remove	= tangox_wdt_remove,
> +	.driver	= {
> +		.name		= "tangox-wdt",
> +		.of_match_table	= tangox_wdt_dt_ids,
> +	},
> +};
> +
> +module_platform_driver(tangox_wdt_driver);
> +
> +MODULE_AUTHOR("Mans Rullgard <mans@mansr.com>");
> +MODULE_DESCRIPTION("SMP86xx/SMP87xx Watchdog driver");
> +MODULE_LICENSE("GPL");
>