Re: [PATCH v2] watchdog: tqmx86: Add watchdog driver for the IO controller

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

On 12/9/18 12:08 PM, Andrew Lunn wrote:
> Some TQ-Systems ComExpress modules have an IO controller with a
> watchdog time.
> 
watchdog timer ?

> Signed-off-by: Andrew Lunn <andrew@lunn.ch>
> ---
> v2:
> Fix various typos
> Sort header files
> Use watchdog_init_timeout(() to handle module parameter
> Get core to validate timeout
> Remove redundant ping function
> Remove redundant stop function
> Use devm_watchdog_register_device allowing release to be removed
> Use WATCHDOG_NOWAYOUT
> ---
>   drivers/watchdog/Kconfig      |  12 ++++
>   drivers/watchdog/Makefile     |   1 +
>   drivers/watchdog/tqmx86_wdt.c | 126 ++++++++++++++++++++++++++++++++++
>   3 files changed, 139 insertions(+)
>   create mode 100644 drivers/watchdog/tqmx86_wdt.c
> 
> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> index 2d64333f4782..7c7528e8644b 100644
> --- a/drivers/watchdog/Kconfig
> +++ b/drivers/watchdog/Kconfig
> @@ -1308,6 +1308,18 @@ config SMSC37B787_WDT
>   
>   	  Most people will say N.
>   
> +config TQMX86_WDT
> +	tristate "TQ-Systems TQMX86 Watchdog Timer"
> +	depends on X86
> +	help
> +	This is the driver for the hardware watchdog timer in the TQMN86 IO

TQMN86 or TQMX86 ?

> +	controller found on some of their ComExpress Modules.
> +
> +	To compile this driver as a module, choose M here; the module
> +	will be called tqmx86_wdt.
> +
> +	Most people will say N.
> +
>   config VIA_WDT
>   	tristate "VIA Watchdog Timer"
>   	depends on X86 && PCI
> diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
> index f69cdff5ad7f..b077e35414e2 100644
> --- a/drivers/watchdog/Makefile
> +++ b/drivers/watchdog/Makefile
> @@ -129,6 +129,7 @@ obj-$(CONFIG_SBC7240_WDT) += sbc7240_wdt.o
>   obj-$(CONFIG_CPU5_WDT) += cpu5wdt.o
>   obj-$(CONFIG_SMSC_SCH311X_WDT) += sch311x_wdt.o
>   obj-$(CONFIG_SMSC37B787_WDT) += smsc37b787_wdt.o
> +obj-$(CONFIG_TQMX86_WDT) += tqmx86_wdt.o
>   obj-$(CONFIG_VIA_WDT) += via_wdt.o
>   obj-$(CONFIG_W83627HF_WDT) += w83627hf_wdt.o
>   obj-$(CONFIG_W83877F_WDT) += w83877f_wdt.o
> diff --git a/drivers/watchdog/tqmx86_wdt.c b/drivers/watchdog/tqmx86_wdt.c
> new file mode 100644
> index 000000000000..9d2ff7bcb061
> --- /dev/null
> +++ b/drivers/watchdog/tqmx86_wdt.c
> @@ -0,0 +1,126 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Watchdog driver for TQMx86 PLD.
> + *
> + * The watchdog supports power of 2 timeouts from 1 to 4096sec.
> + * Once started, it cannot be stopped.
> + */
> +
> +#include <linux/io.h>
> +#include <linux/log2.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/timer.h>
> +#include <linux/watchdog.h>
> +
> +/* default timeout (secs) */
> +#define WDT_TIMEOUT 32
> +
> +static unsigned int timeout;
> +module_param(timeout, uint, 0);
> +MODULE_PARM_DESC(timeout,
> +	"Watchdog timeout in seconds. (1<=timeout<=4096, default="
> +				__MODULE_STRING(WDT_TIMEOUT) ")");
> +struct tqmx86_wdt {
> +	struct watchdog_device wdd;
> +	void __iomem *io_base;
> +};
> +
> +#define TQMX86_WDCFG	0x00 /* Watchdog Configuration Register */
> +#define TQMX86_WDCS	0x01 /* Watchdog Config/Status Register */
> +
> +static int tqmx86_wdt_start(struct watchdog_device *wdd)
> +{
> +	struct tqmx86_wdt *priv = watchdog_get_drvdata(wdd);
> +
> +	iowrite8(0x81, priv->io_base + TQMX86_WDCS);
> +
> +	return 0;
> +}
> +
> +static int tqmx86_wdt_set_timeout(struct watchdog_device *wdd,
> +				  unsigned int new_timeout)
> +{
> +	struct tqmx86_wdt *priv = watchdog_get_drvdata(wdd);
> +	u8 val;
> +
> +	timeout = roundup_pow_of_two(new_timeout);

This won't work as (I think it is) intended. 'timeout' is the global
variable. This function is called from the probe function with
WDT_TIMEOUT as parameter. The overwritten variable is then later
used in the call to watchdog_init_timeout(). This means that any
value passed as module parameter will be ignored.

You could just reassign the value to new_timeout; there is no need
for a second variable here. I would also suggest to just use 't'
as variable name, but that is really optional.

> +	val = ilog2(timeout) | 0x90;
> +	val += 3; /* values 0,1,2 correspond to 0.125,0.25,0.5s timeouts */
> +	iowrite8(val, priv->io_base + TQMX86_WDCFG);
> +
> +	wdd->timeout = timeout;
> +
> +	return 0;
> +}
> +
> +static const struct watchdog_info tqmx86_wdt_info = {
> +	.options	= WDIOF_SETTIMEOUT |
> +			  WDIOF_KEEPALIVEPING,
> +	.identity	= "TQMx86 Watchdog",
> +};
> +
> +static struct watchdog_ops tqmx86_wdt_ops = {
> +	.owner		= THIS_MODULE,
> +	.start		= tqmx86_wdt_start,
> +	.set_timeout	= tqmx86_wdt_set_timeout,
> +};
> +
> +static int tqmx86_wdt_probe(struct platform_device *pdev)
> +{
> +	struct tqmx86_wdt *priv;
> +	struct resource *res;
> +	int err;
> +
> +	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
> +	if (!priv)
> +		return -ENOMEM;
> +
> +	res = platform_get_resource(pdev, IORESOURCE_IO, 0);
> +	if (IS_ERR(res))
> +		return PTR_ERR(res);
> +
> +	priv->io_base = devm_ioport_map(&pdev->dev, res->start,
> +					resource_size(res));
> +	if (IS_ERR(priv->io_base))
> +		return PTR_ERR(priv->io_base);
> +
> +	platform_set_drvdata(pdev, priv);

Unless I am missing something, this is no longer needed
(no remove function).

> +	watchdog_set_drvdata(&priv->wdd, priv);
> +
> +	tqmx86_wdt_set_timeout(&priv->wdd, WDT_TIMEOUT);
> +
It might be better to call this with wdd->timeout as parameter
after the call to watchdog_init_timeout(). This would set it
to the value you actually want (and update wdd->timeout to a
supported value if it was set with a module parameter).

> +	priv->wdd.parent = &pdev->dev;
> +	priv->wdd.info = &tqmx86_wdt_info;
> +	priv->wdd.ops = &tqmx86_wdt_ops;
> +	priv->wdd.min_timeout = 1;
> +	priv->wdd.max_timeout = 4096;
> +	priv->wdd.max_hw_heartbeat_ms = 4096*1000;
> +	priv->wdd.timeout = WDT_TIMEOUT;
> +
> +	watchdog_init_timeout(&priv->wdd, timeout, &pdev->dev);
> +
> +	watchdog_set_nowayout(&priv->wdd, WATCHDOG_NOWAYOUT);
> +
> +	err = devm_watchdog_register_device(&pdev->dev, &priv->wdd);
> +	if (err)
> +		return err;
> +
> +	dev_info(&pdev->dev, "TQMx86 watchdog\n");
> +
> +	return 0;
> +}
> +
> +static struct platform_driver tqmx86_wdt_driver = {
> +	.driver		= {
> +		.name	= "tqmx86-wdt",
> +	},
> +	.probe		= tqmx86_wdt_probe,
> +};
> +
> +module_platform_driver(tqmx86_wdt_driver);
> +
> +MODULE_AUTHOR("Vadim V.Vlasov <vvlasov@dev.rtsoft.ru>");
> +MODULE_DESCRIPTION("TQMx86 Watchdog");
> +MODULE_ALIAS("platform:tqmx86-wdt");
> +MODULE_LICENSE("GPL");
>