Re: [v3,4/4] watchdog: add Gateworks System Controller support

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

On Wed, Mar 28, 2018 at 08:14:03AM -0700, Tim Harvey wrote:
> Signed-off-by: Tim Harvey <tharvey@gateworks.com>
> ---
>  drivers/watchdog/Kconfig   |  10 ++++
>  drivers/watchdog/Makefile  |   1 +
>  drivers/watchdog/gsc_wdt.c | 146 +++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 157 insertions(+)
>  create mode 100644 drivers/watchdog/gsc_wdt.c
> 
> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> index ca200d1..c9d4b2e 100644
> --- a/drivers/watchdog/Kconfig
> +++ b/drivers/watchdog/Kconfig
> @@ -150,6 +150,16 @@ config GPIO_WATCHDOG_ARCH_INITCALL
>  	  arch_initcall.
>  	  If in doubt, say N.
>  
> +config GSC_WATCHDOG
> +	tristate "Gateworks System Controller (GSC) Watchdog support"
> +	depends on MFD_GATEWORKS_GSC
> +	select WATCHDOG_CORE
> +	help
> +	  Say Y here to include support for the GSC Watchdog.
> +
> +	  This driver can also be built as a module. If so the module
> +	  will be called gsc_wdt.
> +
>  config MENF21BMC_WATCHDOG
>  	tristate "MEN 14F021P00 BMC Watchdog"
>  	depends on MFD_MENF21BMC || COMPILE_TEST
> diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
> index 715a210..499327e 100644
> --- a/drivers/watchdog/Makefile
> +++ b/drivers/watchdog/Makefile
> @@ -215,6 +215,7 @@ 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-$(CONFIG_GSC_WATCHDOG)	+= gsc_wdt.o
>  obj-$(CONFIG_TANGOX_WATCHDOG) += tangox_wdt.o
>  obj-$(CONFIG_WDAT_WDT) += wdat_wdt.o
>  obj-$(CONFIG_WM831X_WATCHDOG) += wm831x_wdt.o
> diff --git a/drivers/watchdog/gsc_wdt.c b/drivers/watchdog/gsc_wdt.c
> new file mode 100644
> index 0000000..b43d083
> --- /dev/null
> +++ b/drivers/watchdog/gsc_wdt.c
> @@ -0,0 +1,146 @@
> +/* SPDX-License-Identifier: GPL-2.0
> + *
> + * Copyright (C) 2018 Gateworks Corporation
> + *
> + * This driver registers a Linux Watchdog for the GSC
> + */
> +#include <linux/mfd/gsc.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/regmap.h>
> +#include <linux/watchdog.h>
> +
> +#define WDT_DEFAULT_TIMEOUT	60
> +
> +struct gsc_wdt {
> +	struct watchdog_device wdt_dev;
> +	struct gsc_dev *gsc;
> +};
> +
> +static int gsc_wdt_start(struct watchdog_device *wdd)
> +{
> +	struct gsc_wdt *wdt = watchdog_get_drvdata(wdd);
> +	unsigned int reg = (1 << GSC_CTRL_1_WDT_ENABLE);

Please use BIT().

> +	int ret;
> +
> +	dev_dbg(wdd->parent, "%s timeout=%d\n", __func__, wdd->timeout);

I don't think those debug messages add any value.

> +
> +	/* clear first as regmap_update_bits will not write if no change */
> +	ret = regmap_update_bits(wdt->gsc->regmap, GSC_CTRL_1, reg, 0);
> +	if (ret)
> +		return ret;
> +	return regmap_update_bits(wdt->gsc->regmap, GSC_CTRL_1, reg, reg);
> +}
> +
> +static int gsc_wdt_stop(struct watchdog_device *wdd)
> +{
> +	struct gsc_wdt *wdt = watchdog_get_drvdata(wdd);
> +	unsigned int reg = (1 << GSC_CTRL_1_WDT_ENABLE);
> +

BIT(). You might as well drop the variable and just use
BIT(GSC_CTRL_1_WDT_ENABLE) below.

> +	dev_dbg(wdd->parent, "%s\n", __func__);
> +
> +	return regmap_update_bits(wdt->gsc->regmap, GSC_CTRL_1, reg, 0);
> +}
> +
> +static int gsc_wdt_set_timeout(struct watchdog_device *wdd,
> +			       unsigned int timeout)
> +{
> +	struct gsc_wdt *wdt = watchdog_get_drvdata(wdd);
> +	unsigned int long_sel = 0;
> +
> +	dev_dbg(wdd->parent, "%s: %d\n", __func__, timeout);
> +
> +	switch (timeout) {
> +	case 60:
> +		long_sel = (1 << GSC_CTRL_1_WDT_TIME);
> +	case 30:
> +		regmap_update_bits(wdt->gsc->regmap, GSC_CTRL_1,
> +				   (1 << GSC_CTRL_1_WDT_TIME),

BIT()

> +				   (long_sel << GSC_CTRL_1_WDT_TIME));
> +		wdd->timeout = timeout;
> +		return 0;
> +	}

Please use rounding and accept other values as well. We don't want to let
user space guessing valid timeouts. 

> +
> +	return -EINVAL;
> +}
> +
> +static const struct watchdog_info gsc_wdt_info = {
> +	.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING,

Please confirm that WDIOF_MAGICCLOSE is not set on purpose.

> +	.identity = "GSC Watchdog"
> +};
> +
> +static const struct watchdog_ops gsc_wdt_ops = {
> +	.owner		= THIS_MODULE,
> +	.start		= gsc_wdt_start,
> +	.stop		= gsc_wdt_stop,
> +	.set_timeout	= gsc_wdt_set_timeout,
> +};
> +
> +static int gsc_wdt_probe(struct platform_device *pdev)
> +{
> +	struct gsc_dev *gsc = dev_get_drvdata(pdev->dev.parent);
> +	struct device *dev = &pdev->dev;
> +	struct gsc_wdt *wdt;
> +	int ret;
> +	unsigned int reg;
> +
> +	wdt = devm_kzalloc(dev, sizeof(*wdt), GFP_KERNEL);
> +	if (!wdt)
> +		return -ENOMEM;
> +
> +	/* ensure GSC fw supports WD functionality */
> +	if (gsc->fwver < 44) {

What if gsc is NULL ?

> +		dev_err(dev, "fw v44 or newer required for wdt function\n");
> +		return -EINVAL;
> +	}
> +
> +	/* ensure WD bit enabled */
> +	if (regmap_read(gsc->regmap, GSC_CTRL_1, &reg))
> +		return -EIO;
> +	if (!(reg & (1 << GSC_CTRL_1_WDT_ENABLE))) {

BIT()

> +		dev_err(dev, "not enabled - must be manually enabled\n");

This doesn't make sense. Bail out if the watchdog is disabled ? Why ?

> +		return -EINVAL;
> +	}
> +
> +	platform_set_drvdata(pdev, wdt);
> +
> +	wdt->gsc = gsc;
> +	wdt->wdt_dev.info = &gsc_wdt_info;
> +	wdt->wdt_dev.ops = &gsc_wdt_ops;
> +	wdt->wdt_dev.status = 0;

Initializing a data structure which is known to be 0 is not needed
and discouraged.

> +	wdt->wdt_dev.min_timeout = 30;
> +	wdt->wdt_dev.max_timeout = 60;
> +	wdt->wdt_dev.parent = dev;
> +
> +	watchdog_set_nowayout(&wdt->wdt_dev, 1);

WATCHDOG_NOWAYOUT ?

> +	watchdog_init_timeout(&wdt->wdt_dev, WDT_DEFAULT_TIMEOUT, dev);

This is quite pointless. If you don't want to support setting the timeout
through devicetree or through a module parameter, just set the timeout
directly above.

> +
> +	watchdog_set_drvdata(&wdt->wdt_dev, wdt);
> +	ret = devm_watchdog_register_device(dev, &wdt->wdt_dev);
> +	if (ret)
> +		return ret;
> +
> +	dev_info(dev, "watchdog driver (timeout=%d sec)\n",
> +		 wdt->wdt_dev.timeout);
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id gsc_wdt_dt_ids[] = {
> +	{ .compatible = "gw,gsc-watchdog", },
> +	{}
> +};
> +
> +static struct platform_driver gsc_wdt_driver = {
> +	.probe		= gsc_wdt_probe,
> +	.driver		= {
> +		.name	= "gsc-wdt",
> +		.of_match_table = gsc_wdt_dt_ids,
> +	},
> +};
> +
> +module_platform_driver(gsc_wdt_driver);
> +
> +MODULE_AUTHOR("Tim Harvey <tharvey@gateworks.com>");
> +MODULE_DESCRIPTION("Gateworks System Controller Watchdog driver");
> +MODULE_LICENSE("GPL v2");