Re: [PATCH v2] watchdog: nic7018_wdt: Add NIC7018 watchdog driver

[Hui Chun Ong <hui.chun.ong@ni.com>]

On Thu, 2016-11-24 at 11:56 -0800, Guenter Roeck wrote:
> On 11/15/2016 07:21 PM, Hui Chun Ong wrote:
> > 
> > Add support for the watchdog timer on PXI Embedded Controller.
> > 
> > Signed-off-by: Hui Chun Ong <hui.chun.ong@ni.com>
> > ---
> > v1: Remove non-standard attributes.
> >     Change from acpi_driver to platform_driver.
> >     Rename driver from ni7018_wdt to nic7018_wdt.
> > ---
> >  Documentation/watchdog/watchdog-parameters.txt |   5 +
> >  drivers/watchdog/Kconfig                       |  10 +
> >  drivers/watchdog/Makefile                      |   1 +
> >  drivers/watchdog/nic7018_wdt.c                 | 303 +++++++++++++++++++++++++
> >  4 files changed, 319 insertions(+)
> >  create mode 100644 drivers/watchdog/nic7018_wdt.c
> > 
> > diff --git a/Documentation/watchdog/watchdog-parameters.txt b/Documentation/watchdog/watchdog-parameters.txt
> > index a8d3642..bd142fa 100644
> > --- a/Documentation/watchdog/watchdog-parameters.txt
> > +++ b/Documentation/watchdog/watchdog-parameters.txt
> > @@ -209,6 +209,11 @@ timeout: Initial watchdog timeout in seconds (0
> >  nowayout: Watchdog cannot be stopped once started
> >  	(default=kernel config parameter)
> >  -------------------------------------------------
> > +nic7018_wdt:
> > +timeout: Initial watchdog timeout in seconds (0
> > +nowayout: Watchdog cannot be stopped once started
> > +	(default=kernel config parameter)
> > +-------------------------------------------------
> >  nuc900_wdt:
> >  heartbeat: Watchdog heartbeats in seconds.
> >  	(default = 15)
> > diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> > index fdd3228..79fb224 100644
> > --- a/drivers/watchdog/Kconfig
> > +++ b/drivers/watchdog/Kconfig
> > @@ -1325,6 +1325,16 @@ config NI903X_WDT
> >  	  To compile this driver as a module, choose M here: the module will be
> >  	  called ni903x_wdt.
> > 
> > +config NIC7018_WDT
> > +	tristate "NIC7018 Watchdog"
> > +	depends on X86 && ACPI
> > +	select WATCHDOG_CORE
> > +	---help---
> > +	  This is the device driver for National Instruments NIC7018 Watchdog.
> > +
> This should describe what the watchdog is for.
> 
> "Support for National Instruments NIC7018 Watchdog".
> 
> > 
> > +	  To compile this driver as a module, choose M here: the module will be
> > +	  called nic7018_wdt.
> > +
> >  # M32R Architecture
> > 
> >  # M68K Architecture
> > diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
> > index caa9f4a..bd88e2e 100644
> > --- a/drivers/watchdog/Makefile
> > +++ b/drivers/watchdog/Makefile
> > @@ -139,6 +139,7 @@ obj-$(CONFIG_INTEL_SCU_WATCHDOG) += intel_scu_watchdog.o
> >  obj-$(CONFIG_INTEL_MID_WATCHDOG) += intel-mid_wdt.o
> >  obj-$(CONFIG_INTEL_MEI_WDT) += mei_wdt.o
> >  obj-$(CONFIG_NI903X_WDT) += ni903x_wdt.o
> > +obj-$(CONFIG_NIC7018_WDT) += nic7018_wdt.o
> > 
> >  # M32R Architecture
> > 
> > diff --git a/drivers/watchdog/nic7018_wdt.c b/drivers/watchdog/nic7018_wdt.c
> > new file mode 100644
> > index 0000000..780edc6
> > --- /dev/null
> > +++ b/drivers/watchdog/nic7018_wdt.c
> > @@ -0,0 +1,303 @@
> > +/*
> > + * Copyright (C) 2016 National Instruments Corp.
> > + *
> > + * 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.
> > + *
> > + * This program is distributed in the hope that it will be useful,
> > + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> > + * GNU General Public License for more details.
> > + */
> > +
> > +#include 
> > +#include 
> > +#include 
> > +#include 
> > +#include 
> > +#include 
> > +#include 
> > +
> > +#define LOCK			0xA5
> > +#define UNLOCK			0x5A
> > +
> > +#define WDT_CTRL_RESET_EN	BIT(7)
> > +#define WDT_RELOAD_PORT_EN	BIT(7)
> > +
> Should include linux/bitops.h
> 
> > 
> > +#define WDT_CTRL		1
> > +#define WDT_RELOAD_CTRL		2
> > +#define WDT_PRESET_PRESCALE	4
> > +#define WDT_REG_LOCK		5
> > +#define WDT_COUNT		6
> > +#define WDT_RELOAD_PORT		7
> > +
> > +#define WDT_MIN_TIMEOUT		1
> > +#define WDT_MAX_TIMEOUT		464
> 32 * 15 would be 480 ? I assume the limit above is because of the rounding down
> by 16 in the driver, but that only shows that this rounding is maybe not the best
> idea. After all, the maximum timeout _is_ 480 seconds, if I understand the code
> correctly.
> 
The formula for timeout calculation is = (period * counter) - (period / 2). So in this case, (32 * 15) - (32 / 2) = 464

> > 
> > +#define WDT_DEFAULT_TIMEOUT	80
> > +
> Kind of an odd number, as it can not really be expressed by the hardware.
> The real timeout, if I understand the code correctly, would be 96 (32 * 3)
> seconds. Another data point that the rounding as implemented isn't necessarily
> the best possible implementation.
> 
The timeout based on formula above is (32 * 3) - (32 / 16) = 80

> > 
> > +#define WDT_IO_SIZE		8
> > +#define WDT_MAX_COUNTER		15
> > +
> > +static unsigned int timeout;
> > +module_param(timeout, uint, 0);
> > +MODULE_PARM_DESC(timeout,
> > +		 "Watchdog timeout in seconds. (default="
> > +		 __MODULE_STRING(WDT_DEFAULT_TIMEOUT) ")");
> > +
> > +static int nowayout = WATCHDOG_NOWAYOUT;
> > +module_param(nowayout, int, S_IRUGO);
> S_IRUGO is out of favor nowadays. Just use 0444.
> Sure you want this readable, though ? That is quite unusual.
> 
> > 
> > +MODULE_PARM_DESC(nowayout,
> > +		 "Watchdog cannot be stopped once started. (default="
> > +		 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
> > +
> > +struct nic7018_wdt {
> > +	u16 io_base;
> > +	u32 period_ms;
> > +	struct mutex lock;
> This lock is not necessary. The watchdog core already provides locking.
> 
> > 
> > +	struct watchdog_device wdd;
> > +	struct platform_device *pdev;
> pdev isn't used anywhere.
> 
> > 
> > +};
> > +
> > +struct nic7018_config {
> > +	u32 period_ms;
> > +	u8 divider;
> > +};
> > +
> > +static const struct nic7018_config nic7018_configs[] = {
> > +	{   125, 3 },
> > +	{  2000, 4 },
> > +	{ 32000, 5 },
> > +};
> > +
> > +static inline u32 nic7018_timeout_ms(u32 period_ms, u8 counter)
> > +{
> > +	return period_ms * counter - period_ms / 2;
> > +}
> > +
> > +static const struct nic7018_config *nic7018_get_config(u32 timeout_ms,
> > +						       u8 *counter)
> > +{
> > +	u32 delta, i, best_delta = U32_MAX;
> > +	const struct nic7018_config *config, *best_config = NULL;
> > +	u8 count;
> > +
> > +	for (i = 0; i < ARRAY_SIZE(nic7018_configs); i++) {
> > +		config = &nic7018_configs[i];
> > +
> > +		count = DIV_ROUND_UP(timeout_ms + config->period_ms / 2,
> > +				     config->period_ms);
> > +
> > +		if (count > WDT_MAX_COUNTER)
> > +			continue;
> > +
> > +		delta = nic7018_timeout_ms(config->period_ms, count) -
> > +			timeout_ms;
> > +
> > +		if (delta < best_delta) {
> > +			best_delta = delta;
> > +			best_config = config;
> > +			*counter = count;
> > +		}
> > +	}
> > +	return best_config;
> > +}
> > +
> This appears overly complex. Ultimately it boils down to something like
> 
> 	if (timeout_ms <= 125 * (WDT_MAX_COUNTER + 8) {
> 		*counter = min(WDT_MAX_COUNTER, DIV_ROUND_UP(timeout_ms, 125));
> 		return  &config[0];
> 	} else if (timeout_ms <= 2000 * (WDT_MAX_COUNTER + 8) {
> 		*counter = min(WDT_MAX_COUNTER, DIV_ROUND_UP(timeout_ms, 2000));
> 		return &config[1];
> 	}
> 	*counter = min(WDT_MAX_COUNTER, DIV_ROUND_UP(timeout_ms, 32000));
> 	return &config[2];
> 
> or, if you want to be fancy,
> 
> 	for (i = 0; i < ARRAY_SIZE(nic7018_configs); i++) {
> 		config = &nic7018_configs[i];
> 		if (timeout_ms <= config->period_ms * (WDT_MAX_COUNTER + 8))
> 			break;
> 	}
> 	*counter = min(WDT_MAX_COUNTER, DIV_ROUND_UP(timeout_ms, config->period_ms));
> 	return config;
> 
> > 
> > +static int nic7018_set_timeout(struct watchdog_device *wdd,
> > +			       unsigned int timeout)
> > +{
> > +	struct nic7018_wdt *wdt = watchdog_get_drvdata(wdd);
> > +	const struct nic7018_config *config;
> > +	u8 counter;
> > +
> > +	config = nic7018_get_config(timeout * 1000, &counter);
> > +	if (!config)
> > +		return -EINVAL;
> This is not necessary. The maximum timeout guarantees that the core will not request
> a larger timeout than supported. Just have nic7018_get_config() never return an error
> (as suggested above).
> 
> > 
> > +
> > +	mutex_lock(&wdt->lock);
> > +	outb(counter << 4 | config->divider,
> > +	     wdt->io_base + WDT_PRESET_PRESCALE);
> > +
> > +	wdd->timeout = nic7018_timeout_ms(config->period_ms, counter) / 1000;
> > +	wdt->period_ms = config->period_ms;
> > +	mutex_unlock(&wdt->lock);
> > +
> > +	return 0;
> > +}
> > +
> > +static int nic7018_start(struct watchdog_device *wdd)
> > +{
> > +	struct nic7018_wdt *wdt = watchdog_get_drvdata(wdd);
> > +	u8 control;
> > +
> > +	nic7018_set_timeout(wdd, wdd->timeout);
> > +
> Side note: As currently written, the above function can return an error
> (in theory). If that was the case, the code below would have more or less random
> results.
> 
> > 
> > +	mutex_lock(&wdt->lock);
> > +	control = inb(wdt->io_base + WDT_RELOAD_CTRL);
> > +	outb(control | WDT_RELOAD_PORT_EN, wdt->io_base + WDT_RELOAD_CTRL);
> > +
> > +	outb(1, wdt->io_base + WDT_RELOAD_PORT);
> > +
> > +	control = inb(wdt->io_base + WDT_CTRL);
> > +	outb(control | WDT_CTRL_RESET_EN, wdt->io_base + WDT_CTRL);
> > +	mutex_unlock(&wdt->lock);
> > +
> > +	return 0;
> > +}
> > +
> > +static int nic7018_stop(struct watchdog_device *wdd)
> > +{
> > +	struct nic7018_wdt *wdt = watchdog_get_drvdata(wdd);
> > +
> > +	mutex_lock(&wdt->lock);
> > +	outb(0, wdt->io_base + WDT_CTRL);
> > +	outb(0, wdt->io_base + WDT_RELOAD_CTRL);
> > +	outb(0xF0, wdt->io_base + WDT_PRESET_PRESCALE);
> > +	mutex_unlock(&wdt->lock);
> > +
> > +	return 0;
> > +}
> > +
> > +static int nic7018_ping(struct watchdog_device *wdd)
> > +{
> > +	struct nic7018_wdt *wdt = watchdog_get_drvdata(wdd);
> > +
> > +	mutex_lock(&wdt->lock);
> > +	outb(1, wdt->io_base + WDT_RELOAD_PORT);
> > +	mutex_unlock(&wdt->lock);
> > +
> > +	return 0;
> > +}
> > +
> > +static unsigned int nic7018_get_timeleft(struct watchdog_device *wdd)
> > +{
> > +	struct nic7018_wdt *wdt = watchdog_get_drvdata(wdd);
> > +	u8 count;
> > +
> > +	mutex_lock(&wdt->lock);
> > +	count = inb(wdt->io_base + WDT_COUNT) & 0xF;
> > +	mutex_unlock(&wdt->lock);
> > +
> > +	if (!count)
> > +		return 0;
> > +
> This is only needed because of the rounding down in nic7018_timeout_ms().
> I am not really sure if that rounding adds any real value, especially
> since the result is then divided by 1000 without rounding. From my
> perspective, all it does is to add complexity. I would suggest to just return
> wdt->period_ms * count / 1000, or, if you want to be fancy,
> DIV_ROUND_CLOSEST(wdt->period_ms * count, 1000).
> 
> > 
> > +	return nic7018_timeout_ms(wdt->period_ms, count) / 1000;
> > +}
> > +
> > +static const struct watchdog_info nic7018_wdd_info = {
> > +	.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
> > +	.identity = "NIC7018 Watchdog",
> > +};
> > +
> > +static const struct watchdog_ops nic7018_wdd_ops = {
> > +	.owner = THIS_MODULE,
> > +	.start = nic7018_start,
> > +	.stop = nic7018_stop,
> > +	.ping = nic7018_ping,
> > +	.set_timeout = nic7018_set_timeout,
> > +	.get_timeleft = nic7018_get_timeleft,
> > +};
> > +
> > +static int nic7018_probe(struct platform_device *pdev)
> > +{
> > +	struct device *dev = &pdev->dev;
> > +	struct watchdog_device *wdd;
> > +	struct nic7018_wdt *wdt;
> > +	struct resource *io_rc;
> > +	int ret;
> > +
> > +	wdt = devm_kzalloc(dev, sizeof(*wdt), GFP_KERNEL);
> > +	if (!wdt)
> > +		return -ENOMEM;
> > +
> > +	wdt->pdev = pdev;
> > +	platform_set_drvdata(pdev, wdt);
> > +
> > +	io_rc = platform_get_resource(pdev, IORESOURCE_IO, 0);
> > +	if (!io_rc) {
> > +		dev_err(dev, "missing IO resources\n");
> > +		return -EINVAL;
> > +	}
> > +
> > +	if (resource_size(io_rc) < WDT_IO_SIZE) {
> > +		dev_err(dev, "IO region too small\n");
> > +		return -EINVAL;
> > +	}
> > +
> It is highly unusual to check the resource size. I would suggest to drop it.
> Also, please use devm_ioremap_resource(), which returns an error code.
> With that, you don't have to check the error code from platform_get_resource();
> devm_ioremap_resource() does it for you.
> 	io_rc = platform_get_resource(pdev, IORESOURCE_IO, 0);
> 	wdt->io_base = devm_ioremap_resource(dev, res);
> 	if (IS_ERR(wdt->io_base))
> 		return PTR_ERR(wdt->io_base);
> 
Not sure if I understand. Isn't "devm_ioremap_resource" only accept IORESOURCE_MEM not IORESOURCE_IO?

> > 
> > +	if (!devm_request_region(dev, io_rc->start, resource_size(io_rc),
> > +				 KBUILD_MODNAME)) {
> > +		dev_err(dev, "failed to get IO region\n");
> > +		return -EBUSY;
> > +	}
> > +
> > +	wdt->io_base = io_rc->start;
> > +	mutex_init(&wdt->lock);
> > +
> > +	wdd = &wdt->wdd;
> > +	wdd->info = &nic7018_wdd_info;
> > +	wdd->ops = &nic7018_wdd_ops;
> > +	wdd->min_timeout = WDT_MIN_TIMEOUT;
> > +	wdd->max_timeout = WDT_MAX_TIMEOUT;
> > +	wdd->timeout = WDT_DEFAULT_TIMEOUT;
> > +	wdd->parent = dev;
> > +
> > +	watchdog_set_drvdata(wdd, wdt);
> > +	watchdog_set_nowayout(wdd, nowayout);
> > +
> > +	ret = watchdog_init_timeout(wdd, timeout, dev);
> > +	if (ret)
> > +		dev_err(dev, "unable to set timeout value, using default\n");
> If this is an error, the code whould abort. Either make it a warning, or abort.
> 
> > 
> > +
> > +	/* Unlock WDT register */
> > +	outb(UNLOCK, wdt->io_base + WDT_REG_LOCK);
> > +
> > +	ret = watchdog_register_device(wdd);
> > +	if (ret) {
> > +		dev_err(dev, "failed to register watchdog\n");
> > +		goto err_out;
> No output to WDT_REG_LOCK needed here ?
> 
> > 
> > +	}
> > +
> > +	dev_dbg(dev, "io_base=0x%04X, timeout=%d, nowayout=%d\n",
> > +		wdt->io_base, timeout, nowayout);
> > +	return 0;
> > +
> > +err_out:
> > +	mutex_destroy(&wdt->lock);
> > +	return ret;
> > +}
> > +
> > +static int nic7018_remove(struct platform_device *pdev)
> > +{
> > +	struct nic7018_wdt *wdt = platform_get_drvdata(pdev);
> > +
> > +	nic7018_stop(&wdt->wdd);
> > +	watchdog_unregister_device(&wdt->wdd);
> > +
> > +	/* Lock WDT register */
> > +	outb(LOCK, wdt->io_base + WDT_REG_LOCK);
> > +
> > +	mutex_destroy(&wdt->lock);
> > +	return 0;
> > +}
> > +
> > +static const struct acpi_device_id nic7018_device_ids[] = {
> > +	{"NIC7018", 0},
> > +	{"", 0},
> > +};
> > +MODULE_DEVICE_TABLE(acpi, nic7018_device_ids);
> > +
> > +static struct platform_driver watchdog_driver = {
> > +	.probe = nic7018_probe,
> > +	.remove = nic7018_remove,
> > +	.driver = {
> > +		.name = KBUILD_MODNAME,
> > +		.acpi_match_table = ACPI_PTR(nic7018_device_ids),
> > +	},
> > +};
> > +
> > +module_platform_driver(watchdog_driver);
> > +
> > +MODULE_DESCRIPTION("National Instruments NIC7018 Watchdog driver");
> > +MODULE_AUTHOR("Hui Chun Ong <hui.chun.ong@ni.com>");
> > +MODULE_LICENSE("GPL");
> > --
> > 2.7.4
> > 
> > --
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