[PATCH 3/3] watchdog: ds1374_wdt: Introduce Dallas/Maxim DS1374 Watchdog driver

[PATCH 3/3] watchdog: ds1374_wdt: Introduce Dallas/Maxim DS1374 Watchdog driver

[Johnson CH Chen (陳昭勳)]

Here provide Watchdog function from rtc-ds1374.c which is in RTC subsystem
originally. Besides, add nowayout and implement Watchdog margin time when
DS1374 Watchdog device is found.

Signed-off-by: Johnson Chen <johnsonch.chen@moxa.com>
---
 drivers/watchdog/Kconfig      |  11 ++
 drivers/watchdog/Makefile     |   1 +
 drivers/watchdog/ds1374_wdt.c | 330 ++++++++++++++++++++++++++++++++++
 3 files changed, 342 insertions(+)
 create mode 100644 drivers/watchdog/ds1374_wdt.c

diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index b739c476955b..b4ff4b3c18da 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -316,6 +316,17 @@ config ZIIRAVE_WATCHDOG
 	  To compile this driver as a module, choose M here: the
 	  module will be called ziirave_wdt.
 
+config DS1374_WATCHDOG
+	tristate "Dallas/Maxim DS1374 Watchdog timer"
+	depends on MFD_DS1374
+	select WATCHDOG_CORE
+	help
+	  If you say Y here you will get support for the watchdog timer
+	  in the Dallas/Maxim Semiconductor DS1374 real-time clock chips.
+
+	  This driver can also be built as a module. If so the module
+	  will be called ds1374_wdt.
+
 config RAVE_SP_WATCHDOG
 	tristate "RAVE SP Watchdog timer"
 	depends on RAVE_SP_CORE
diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
index 6de2e4ceef19..1c468f5d9e5f 100644
--- a/drivers/watchdog/Makefile
+++ b/drivers/watchdog/Makefile
@@ -224,3 +224,4 @@ obj-$(CONFIG_MENF21BMC_WATCHDOG) += menf21bmc_wdt.o
 obj-$(CONFIG_MENZ069_WATCHDOG) += menz69_wdt.o
 obj-$(CONFIG_RAVE_SP_WATCHDOG) += rave-sp-wdt.o
 obj-$(CONFIG_STPMIC1_WATCHDOG) += stpmic1_wdt.o
+obj-$(CONFIG_DS1374_WATCHDOG) += ds1374_wdt.o
diff --git a/drivers/watchdog/ds1374_wdt.c b/drivers/watchdog/ds1374_wdt.c
new file mode 100644
index 000000000000..ce69e45973fd
--- /dev/null
+++ b/drivers/watchdog/ds1374_wdt.c
@@ -0,0 +1,330 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * RTC client/driver for the Maxim/Dallas DS1374 Real-Time Clock over I2C
+ *
+ * Based on code by Randy Vinson <rvinson@mvista.com>,
+ * which was based on the m41t00.c by Mark Greer <mgreer@mvista.com>.
+ *
+ * Copyright (C) 2020 Johnson Chen <johnsonch.chen@moxa.com>
+ * Copyright (C) 2014 Rose Technology
+ * Copyright (C) 2006-2007 Freescale Semiconductor
+ * Copyright (C) 2005 MontaVista Software, Inc.
+ */
+
+/*
+ * It would be more efficient to use i2c msgs/i2c_transfer directly but, as
+ * recommened in .../Documentation/i2c/writing-clients section
+ * "Sending and receiving", using SMBus level communication is preferred.
+ */
+
+#include <linux/kernel.h>
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/ioctl.h>
+#include <linux/reboot.h>
+#include <linux/watchdog.h>
+#include <linux/workqueue.h>
+#include <linux/platform_device.h>
+#include <linux/i2c.h>
+#include <linux/uaccess.h>
+
+#define DEVNAME                 "ds1374_wdt"
+
+#define DS1374_REG_WDALM0	0x04 /* Watchdog/Alarm */
+#define DS1374_REG_WDALM1	0x05
+#define DS1374_REG_WDALM2	0x06
+#define DS1374_REG_CR		0x07 /* Control */
+#define DS1374_REG_CR_AIE	0x01 /* Alarm Int. Enable */
+#define DS1374_REG_CR_WDSTR     0x08 /* 1=INT, 0=RST */
+#define DS1374_REG_CR_WDALM	0x20 /* 1=Watchdog, 0=Alarm */
+#define DS1374_REG_CR_WACE	0x40 /* WD/Alarm counter enable */
+
+/* Default margin */
+#define WD_TIMO                 131762
+#define TIMER_MARGIN_MIN	4096 /* 1s */
+#define TIMER_MARGIN_MAX	(60*60*24*4096) /* one day */
+
+static int wdt_margin = WD_TIMO;
+module_param(wdt_margin, int, 0);
+MODULE_PARM_DESC(wdt_margin, "Watchdog timeout in seconds (default 32s)");
+
+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) ")");
+
+struct ds1374_wdt {
+	struct i2c_client *client;
+	struct watchdog_device *wdt;
+	struct work_struct work;
+
+	/* The mutex protects alarm operations, and prevents a race
+	 * between the enable_irq() in the workqueue and the free_irq()
+	 * in the remove function.
+	 */
+	struct mutex mutex;
+};
+
+static const struct watchdog_info ds1374_wdt_info = {
+	.identity       = DEVNAME,
+	.options        = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING |
+						WDIOF_MAGICCLOSE,
+};
+
+static struct watchdog_device ds1374_wdd;
+
+static int ds1374_wdt_settimeout(struct watchdog_device *wdt,
+					unsigned int timeout)
+{
+	int ret = -ENOIOCTLCMD;
+	u8 buf[4];
+	int cr, i;
+	struct ds1374_wdt *drv_data = watchdog_get_drvdata(wdt);
+
+	ret = cr = i2c_smbus_read_byte_data(drv_data->client, DS1374_REG_CR);
+	if (ret < 0)
+		goto out;
+
+	/* Disable any existing watchdog/alarm before setting the new one */
+	cr &= ~DS1374_REG_CR_WACE;
+
+	ret = i2c_smbus_write_byte_data(drv_data->client, DS1374_REG_CR, cr);
+	if (ret < 0)
+		goto out;
+
+	/* Set new watchdog time */
+	for (i = 0; i < 3; i++) {
+		buf[i] = timeout & 0xff;
+		timeout >>= 8;
+	}
+
+	ret = i2c_smbus_write_i2c_block_data(drv_data->client,
+						DS1374_REG_WDALM0, 3, buf);
+	if (ret) {
+		pr_info("couldn't set new watchdog time\n");
+		goto out;
+	}
+
+	/* Enable watchdog timer */
+	cr |= DS1374_REG_CR_WACE | DS1374_REG_CR_WDALM;
+	cr &= ~DS1374_REG_CR_WDSTR;/* for RST PIN */
+	cr &= ~DS1374_REG_CR_AIE;
+
+	ret = i2c_smbus_write_byte_data(drv_data->client, DS1374_REG_CR, cr);
+	if (ret < 0)
+		goto out;
+
+	return 0;
+out:
+	return ret;
+}
+
+
+/*
+ * Read WD/Alarm counter to reload the watchdog timer. (ie, pat the watchdog)
+ */
+static int ds1374_wdt_ping(struct watchdog_device *wdt)
+{
+	struct ds1374_wdt *drv_data = watchdog_get_drvdata(wdt);
+	int ret;
+	u8 buf[4];
+
+	ret = i2c_smbus_read_i2c_block_data(drv_data->client,
+						DS1374_REG_WDALM0, 3, buf);
+
+	if (ret < 0 || ret < 3)
+		pr_info("WD TICK FAIL!!!!!!!!!! %i\n", ret);
+
+	return ret;
+}
+
+static int ds1374_wdt_start(struct watchdog_device *wdt)
+{
+	int ret;
+
+	ret = ds1374_wdt_settimeout(wdt, wdt_margin);
+	if (ret)
+		return ret;
+
+	ds1374_wdt_ping(wdt);
+
+	return 0;
+}
+
+static int ds1374_wdt_stop(struct watchdog_device *wdt)
+{
+	struct ds1374_wdt *drv_data = watchdog_get_drvdata(wdt);
+	int cr;
+
+	if (nowayout)
+		return 0;
+
+	cr = i2c_smbus_read_byte_data(drv_data->client, DS1374_REG_CR);
+	/* Disable watchdog timer */
+	cr &= ~DS1374_REG_CR_WACE;
+
+	return i2c_smbus_write_byte_data(drv_data->client, DS1374_REG_CR, cr);
+}
+
+/*
+ * Handle commands from user-space.
+ */
+static long ds1374_wdt_ioctl(struct watchdog_device *wdt, unsigned int cmd,
+				unsigned long arg)
+{
+	int new_margin, options;
+
+	switch (cmd) {
+	case WDIOC_GETSUPPORT:
+		return copy_to_user((struct watchdog_info __user *)arg,
+		&ds1374_wdt_info, sizeof(ds1374_wdt_info)) ? -EFAULT : 0;
+
+	case WDIOC_GETSTATUS:
+	case WDIOC_GETBOOTSTATUS:
+		return put_user(0, (int __user *)arg);
+	case WDIOC_KEEPALIVE:
+		ds1374_wdt_ping(wdt);
+		return 0;
+	case WDIOC_SETTIMEOUT:
+		if (get_user(new_margin, (int __user *)arg))
+			return -EFAULT;
+
+		/* the hardware's tick rate is 4096 Hz, so
+		 * the counter value needs to be scaled accordingly
+		 */
+		new_margin <<= 12;
+		if (new_margin < 1 || new_margin > 16777216)
+			return -EINVAL;
+
+		wdt_margin = new_margin;
+		ds1374_wdt_settimeout(wdt, new_margin);
+		ds1374_wdt_ping(wdt);
+		fallthrough;
+	case WDIOC_GETTIMEOUT:
+		/* when returning ... inverse is true */
+		return put_user((wdt_margin >> 12), (int __user *)arg);
+	case WDIOC_SETOPTIONS:
+		if (copy_from_user(&options, (int __user *)arg, sizeof(int)))
+			return -EFAULT;
+
+		if (options & WDIOS_DISABLECARD) {
+			pr_info("disable watchdog\n");
+			ds1374_wdt_stop(wdt);
+			return 0;
+		}
+
+		if (options & WDIOS_ENABLECARD) {
+			pr_info("enable watchdog\n");
+			ds1374_wdt_settimeout(wdt, wdt_margin);
+			ds1374_wdt_ping(wdt);
+			return 0;
+		}
+		return -EINVAL;
+	}
+	return -ENOTTY;
+}
+
+static int ds1374_wdt_notify_sys(struct notifier_block *this,
+			unsigned long code, void *unused)
+{
+	if (code == SYS_DOWN || code == SYS_HALT)
+		/* Disable Watchdog */
+		ds1374_wdt_stop(&ds1374_wdd);
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block ds1374_wdt_notifier = {
+	.notifier_call = ds1374_wdt_notify_sys,
+};
+
+static int ds1374_wdt_probe(struct platform_device *pdev)
+{
+	struct ds1374_wdt *drv_data;
+	struct i2c_client *client = to_i2c_client(pdev->dev.parent);
+	int ret;
+
+	drv_data = devm_kzalloc(&pdev->dev, sizeof(struct ds1374_wdt),
+				GFP_KERNEL);
+	if (!drv_data)
+		return -ENOMEM;
+
+	drv_data->wdt = &ds1374_wdd;
+	drv_data->client = client;
+	mutex_init(&drv_data->mutex);
+
+	watchdog_init_timeout(drv_data->wdt, wdt_margin, &pdev->dev);
+	watchdog_set_nowayout(drv_data->wdt, nowayout);
+
+	watchdog_set_drvdata(drv_data->wdt, drv_data);
+	platform_set_drvdata(pdev, drv_data);
+
+	ret = watchdog_register_device(drv_data->wdt);
+	if (ret) {
+		dev_err(&pdev->dev, "failed to register Watchdog device\n");
+		return ret;
+	}
+
+	ret = register_reboot_notifier(&ds1374_wdt_notifier);
+	if (ret) {
+		watchdog_unregister_device(drv_data->wdt);
+		return ret;
+	}
+
+	ds1374_wdt_settimeout(drv_data->wdt, wdt_margin);
+	dev_info(&pdev->dev, "Dallas/Maxim DS1374 watchdog device enabled\n");
+
+	return 0;
+}
+
+static int ds1374_wdt_remove(struct platform_device *pdev)
+{
+	struct ds1374_wdt *drv_data = platform_get_drvdata(pdev);
+
+	dev_warn(&pdev->dev, "Unregister DS1374 watchdog device\n");
+	watchdog_unregister_device(drv_data->wdt);
+	unregister_reboot_notifier(&ds1374_wdt_notifier);
+
+	return 0;
+}
+
+static void ds1374_wdt_shutdown(struct platform_device *pdev)
+{
+	struct ds1374_wdt *drv_data = platform_get_drvdata(pdev);
+
+	mutex_lock(&drv_data->mutex);
+	ds1374_wdt_stop(drv_data->wdt);
+	mutex_unlock(&drv_data->mutex);
+}
+
+static const struct watchdog_ops ds1374_wdt_fops = {
+	.owner          = THIS_MODULE,
+	.start          = ds1374_wdt_start,
+	.stop           = ds1374_wdt_stop,
+	.ping           = ds1374_wdt_ping,
+	.set_timeout    = ds1374_wdt_settimeout,
+	.ioctl          = ds1374_wdt_ioctl,
+};
+
+static struct watchdog_device ds1374_wdd = {
+	.info           = &ds1374_wdt_info,
+	.ops            = &ds1374_wdt_fops,
+	.min_timeout    = TIMER_MARGIN_MIN,
+	.max_timeout    = TIMER_MARGIN_MAX,
+};
+
+static struct platform_driver ds1374_wdt = {
+	.driver         = {
+		.owner  = THIS_MODULE,
+		.name   = DEVNAME,
+	},
+	.probe          = ds1374_wdt_probe,
+	.remove         = ds1374_wdt_remove,
+	.shutdown       = ds1374_wdt_shutdown,
+};
+
+module_platform_driver(ds1374_wdt);
+
+MODULE_AUTHOR("Johnson Chen <johnsonch.chen@moxa.com>");
+MODULE_DESCRIPTION("Dallas/Maxim DS1374 Watchdog Driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("Platform:ds1374_wdt");
-- 
2.20.1

Re: [PATCH 3/3] watchdog: ds1374_wdt: Introduce Dallas/Maxim DS1374 Watchdog driver

[Guenter Roeck]

On 6/22/20 3:03 AM, Johnson CH Chen (陳昭勳) wrote:
> Here provide Watchdog function from rtc-ds1374.c which is in RTC subsystem
> originally. Besides, add nowayout and implement Watchdog margin time when
> DS1374 Watchdog device is found.
> 
> Signed-off-by: Johnson Chen <johnsonch.chen@moxa.com>
> ---
>  drivers/watchdog/Kconfig      |  11 ++
>  drivers/watchdog/Makefile     |   1 +
>  drivers/watchdog/ds1374_wdt.c | 330 ++++++++++++++++++++++++++++++++++
>  3 files changed, 342 insertions(+)
>  create mode 100644 drivers/watchdog/ds1374_wdt.c
> 
> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> index b739c476955b..b4ff4b3c18da 100644
> --- a/drivers/watchdog/Kconfig
> +++ b/drivers/watchdog/Kconfig
> @@ -316,6 +316,17 @@ config ZIIRAVE_WATCHDOG
>  	  To compile this driver as a module, choose M here: the
>  	  module will be called ziirave_wdt.
>  
> +config DS1374_WATCHDOG
> +	tristate "Dallas/Maxim DS1374 Watchdog timer"
> +	depends on MFD_DS1374
> +	select WATCHDOG_CORE
> +	help
> +	  If you say Y here you will get support for the watchdog timer
> +	  in the Dallas/Maxim Semiconductor DS1374 real-time clock chips.
> +
> +	  This driver can also be built as a module. If so the module
> +	  will be called ds1374_wdt.
> +
>  config RAVE_SP_WATCHDOG
>  	tristate "RAVE SP Watchdog timer"
>  	depends on RAVE_SP_CORE
> diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
> index 6de2e4ceef19..1c468f5d9e5f 100644
> --- a/drivers/watchdog/Makefile
> +++ b/drivers/watchdog/Makefile
> @@ -224,3 +224,4 @@ obj-$(CONFIG_MENF21BMC_WATCHDOG) += menf21bmc_wdt.o
>  obj-$(CONFIG_MENZ069_WATCHDOG) += menz69_wdt.o
>  obj-$(CONFIG_RAVE_SP_WATCHDOG) += rave-sp-wdt.o
>  obj-$(CONFIG_STPMIC1_WATCHDOG) += stpmic1_wdt.o
> +obj-$(CONFIG_DS1374_WATCHDOG) += ds1374_wdt.o
> diff --git a/drivers/watchdog/ds1374_wdt.c b/drivers/watchdog/ds1374_wdt.c
> new file mode 100644
> index 000000000000..ce69e45973fd
> --- /dev/null
> +++ b/drivers/watchdog/ds1374_wdt.c
> @@ -0,0 +1,330 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * RTC client/driver for the Maxim/Dallas DS1374 Real-Time Clock over I2C
> + *
> + * Based on code by Randy Vinson <rvinson@mvista.com>,
> + * which was based on the m41t00.c by Mark Greer <mgreer@mvista.com>.
> + *
> + * Copyright (C) 2020 Johnson Chen <johnsonch.chen@moxa.com>
> + * Copyright (C) 2014 Rose Technology
> + * Copyright (C) 2006-2007 Freescale Semiconductor
> + * Copyright (C) 2005 MontaVista Software, Inc.
> + */
> +
> +/*
> + * It would be more efficient to use i2c msgs/i2c_transfer directly but, as
> + * recommened in .../Documentation/i2c/writing-clients section
> + * "Sending and receiving", using SMBus level communication is preferred.
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/device.h>
> +#include <linux/module.h>
> +#include <linux/ioctl.h>
> +#include <linux/reboot.h>
> +#include <linux/watchdog.h>
> +#include <linux/workqueue.h>
> +#include <linux/platform_device.h>
> +#include <linux/i2c.h>
> +#include <linux/uaccess.h>

Alphabetic order please.

> +
> +#define DEVNAME                 "ds1374_wdt"
> +
> +#define DS1374_REG_WDALM0	0x04 /* Watchdog/Alarm */
> +#define DS1374_REG_WDALM1	0x05
> +#define DS1374_REG_WDALM2	0x06
> +#define DS1374_REG_CR		0x07 /* Control */
> +#define DS1374_REG_CR_AIE	0x01 /* Alarm Int. Enable */
> +#define DS1374_REG_CR_WDSTR     0x08 /* 1=INT, 0=RST */
> +#define DS1374_REG_CR_WDALM	0x20 /* 1=Watchdog, 0=Alarm */
> +#define DS1374_REG_CR_WACE	0x40 /* WD/Alarm counter enable */
> +
> +/* Default margin */
> +#define WD_TIMO                 131762
> +#define TIMER_MARGIN_MIN	4096 /* 1s */
> +#define TIMER_MARGIN_MAX	(60*60*24*4096) /* one day */
> +
> +static int wdt_margin = WD_TIMO;

Sjould not be pre-initialized. Also, 131762 isn't 32 seconds,
it is 131,762 seconds.

> +module_param(wdt_margin, int, 0);
> +MODULE_PARM_DESC(wdt_margin, "Watchdog timeout in seconds (default 32s)");
> +

As a new driver, it would be better to just use the customary "timeout".

> +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) ")");
> +
> +struct ds1374_wdt {
> +	struct i2c_client *client;
> +	struct watchdog_device *wdt;
> +	struct work_struct work;

Not used.

> +
> +	/* The mutex protects alarm operations, and prevents a race
> +	 * between the enable_irq() in the workqueue and the free_irq()
> +	 * in the remove function.
> +	 */

There is no workqueue here, and the remove function is not needed.

> +	struct mutex mutex;
> +};
> +
> +static const struct watchdog_info ds1374_wdt_info = {
> +	.identity       = DEVNAME,
> +	.options        = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING |
> +						WDIOF_MAGICCLOSE,
> +};
> +
> +static struct watchdog_device ds1374_wdd;
> +
Move declaration please.

> +static int ds1374_wdt_settimeout(struct watchdog_device *wdt,
> +					unsigned int timeout)
> +{

How is this synchronized against accesses by the RTC driver ?

> +	int ret = -ENOIOCTLCMD;

Not an appropriate error code here.

> +	u8 buf[4];
> +	int cr, i;
> +	struct ds1374_wdt *drv_data = watchdog_get_drvdata(wdt);
> +
> +	ret = cr = i2c_smbus_read_byte_data(drv_data->client, DS1374_REG_CR);
> +	if (ret < 0)
> +		goto out;

"goto out;" is unnecessary. Just return the error. Same everywhere else below.

> +
> +	/* Disable any existing watchdog/alarm before setting the new one */
> +	cr &= ~DS1374_REG_CR_WACE;
> +
> +	ret = i2c_smbus_write_byte_data(drv_data->client, DS1374_REG_CR, cr);
> +	if (ret < 0)
> +		goto out;
> +
> +	/* Set new watchdog time */
> +	for (i = 0; i < 3; i++) {
> +		buf[i] = timeout & 0xff;
> +		timeout >>= 8;
> +	}

The value passed to this function from the watchdog core is the
timeout in seconds. I don't see a conversion to internal values
here.

> +
> +	ret = i2c_smbus_write_i2c_block_data(drv_data->client,
> +						DS1374_REG_WDALM0, 3, buf);
> +	if (ret) {
> +		pr_info("couldn't set new watchdog time\n");
> +		goto out;
> +	}

> +
> +	/* Enable watchdog timer */
> +	cr |= DS1374_REG_CR_WACE | DS1374_REG_CR_WDALM;
> +	cr &= ~DS1374_REG_CR_WDSTR;/* for RST PIN */
> +	cr &= ~DS1374_REG_CR_AIE;
> +
> +	ret = i2c_smbus_write_byte_data(drv_data->client, DS1374_REG_CR, cr);
> +	if (ret < 0)
> +		goto out;
> +
> +	return 0;

Pointless. Just return ret.

Also, this function needs to store the new timeout in struct watchdog_device.

> +out:
> +	return ret;
> +}
> +
> +
> +/*
> + * Read WD/Alarm counter to reload the watchdog timer. (ie, pat the watchdog)
> + */
> +static int ds1374_wdt_ping(struct watchdog_device *wdt)
> +{
> +	struct ds1374_wdt *drv_data = watchdog_get_drvdata(wdt);
> +	int ret;
> +	u8 buf[4];
> +
> +	ret = i2c_smbus_read_i2c_block_data(drv_data->client,
> +						DS1374_REG_WDALM0, 3, buf);
> +
> +	if (ret < 0 || ret < 3)
> +		pr_info("WD TICK FAIL!!!!!!!!!! %i\n", ret);
> +

This is not an info message, this is an error. Besides, it is just noise.
Just return the error and drop the message.

> +	return ret;
> +}
> +
> +static int ds1374_wdt_start(struct watchdog_device *wdt)
> +{
> +	int ret;
> +
> +	ret = ds1374_wdt_settimeout(wdt, wdt_margin);

This is wrong. The timeout may have been updated by userspace.
It is inappropriate to change it back to the default here.

> +	if (ret)
> +		return ret;
> +
> +	ds1374_wdt_ping(wdt);

Please do not ignore errors.

> +
> +	return 0;
> +}
> +
> +static int ds1374_wdt_stop(struct watchdog_device *wdt)
> +{
> +	struct ds1374_wdt *drv_data = watchdog_get_drvdata(wdt);
> +	int cr;
> +
> +	if (nowayout)
> +		return 0;

Not needed.

> +
> +	cr = i2c_smbus_read_byte_data(drv_data->client, DS1374_REG_CR);
> +	/* Disable watchdog timer */
> +	cr &= ~DS1374_REG_CR_WACE;
> +
> +	return i2c_smbus_write_byte_data(drv_data->client, DS1374_REG_CR, cr);
> +}
> +
> +/*
> + * Handle commands from user-space.
> + */
> +static long ds1374_wdt_ioctl(struct watchdog_device *wdt, unsigned int cmd,
> +				unsigned long arg)

The whole point of using the watchdog subsystem is to not need a local
ioctl function - and most definitely not one that duplicates watchdog
core functionality.

> +{
> +	int new_margin, options;
> +
> +	switch (cmd) {
> +	case WDIOC_GETSUPPORT:
> +		return copy_to_user((struct watchdog_info __user *)arg,
> +		&ds1374_wdt_info, sizeof(ds1374_wdt_info)) ? -EFAULT : 0;
> +
> +	case WDIOC_GETSTATUS:
> +	case WDIOC_GETBOOTSTATUS:
> +		return put_user(0, (int __user *)arg);
> +	case WDIOC_KEEPALIVE:
> +		ds1374_wdt_ping(wdt);
> +		return 0;
> +	case WDIOC_SETTIMEOUT:
> +		if (get_user(new_margin, (int __user *)arg))
> +			return -EFAULT;
> +
> +		/* the hardware's tick rate is 4096 Hz, so
> +		 * the counter value needs to be scaled accordingly
> +		 */
> +		new_margin <<= 12;
> +		if (new_margin < 1 || new_margin > 16777216)
> +			return -EINVAL;
> +
> +		wdt_margin = new_margin;
> +		ds1374_wdt_settimeout(wdt, new_margin);

Is the idea here to bypass the watchdog subsystem's notion of
keeping the timeout in seconds ? If so, that would be wrong
and unacceptable.

> +		ds1374_wdt_ping(wdt);
> +		fallthrough;
> +	case WDIOC_GETTIMEOUT:
> +		/* when returning ... inverse is true */
> +		return put_user((wdt_margin >> 12), (int __user *)arg);
> +	case WDIOC_SETOPTIONS:
> +		if (copy_from_user(&options, (int __user *)arg, sizeof(int)))
> +			return -EFAULT;
> +
> +		if (options & WDIOS_DISABLECARD) {
> +			pr_info("disable watchdog\n");
> +			ds1374_wdt_stop(wdt);
> +			return 0;
> +		}
> +
> +		if (options & WDIOS_ENABLECARD) {
> +			pr_info("enable watchdog\n");
> +			ds1374_wdt_settimeout(wdt, wdt_margin);
> +			ds1374_wdt_ping(wdt);
> +			return 0;
> +		}
> +		return -EINVAL;
> +	}
> +	return -ENOTTY;
> +}
> +
> +static int ds1374_wdt_notify_sys(struct notifier_block *this,
> +			unsigned long code, void *unused)
> +{
> +	if (code == SYS_DOWN || code == SYS_HALT)
> +		/* Disable Watchdog */
> +		ds1374_wdt_stop(&ds1374_wdd);
> +	return NOTIFY_DONE;
> +}
> +
Not needed - see below.

> +static struct notifier_block ds1374_wdt_notifier = {
> +	.notifier_call = ds1374_wdt_notify_sys,
> +};
> +
> +static int ds1374_wdt_probe(struct platform_device *pdev)
> +{
> +	struct ds1374_wdt *drv_data;
> +	struct i2c_client *client = to_i2c_client(pdev->dev.parent);
> +	int ret;
> +
> +	drv_data = devm_kzalloc(&pdev->dev, sizeof(struct ds1374_wdt),
> +				GFP_KERNEL);
> +	if (!drv_data)
> +		return -ENOMEM;
> +
> +	drv_data->wdt = &ds1374_wdd;
> +	drv_data->client = client;
> +	mutex_init(&drv_data->mutex);
> +
> +	watchdog_init_timeout(drv_data->wdt, wdt_margin, &pdev->dev);
> +	watchdog_set_nowayout(drv_data->wdt, nowayout);
> +
> +	watchdog_set_drvdata(drv_data->wdt, drv_data);
> +	platform_set_drvdata(pdev, drv_data);
> +
> +	ret = watchdog_register_device(drv_data->wdt);

Use devm_watchdog_register_device()

> +	if (ret) {
> +		dev_err(&pdev->dev, "failed to register Watchdog device\n");
> +		return ret;
> +	}
> +
> +	ret = register_reboot_notifier(&ds1374_wdt_notifier);

Call watchdog_stop_on_reboot() before calling watchdog_register_device()
instead.

> +	if (ret) {
> +		watchdog_unregister_device(drv_data->wdt);
> +		return ret;
> +	}
> +
> +	ds1374_wdt_settimeout(drv_data->wdt, wdt_margin);

Unnecessary here; called from start function.

> +	dev_info(&pdev->dev, "Dallas/Maxim DS1374 watchdog device enabled\n");
> +
> +	return 0;
> +}
> +
> +static int ds1374_wdt_remove(struct platform_device *pdev)
> +{
> +	struct ds1374_wdt *drv_data = platform_get_drvdata(pdev);
> +
> +	dev_warn(&pdev->dev, "Unregister DS1374 watchdog device\n");
> +	watchdog_unregister_device(drv_data->wdt);
> +	unregister_reboot_notifier(&ds1374_wdt_notifier);
> +

Call watchdog_stop_on_unregister() before calling watchdog_register_device().

> +	return 0;
> +}
> +
> +static void ds1374_wdt_shutdown(struct platform_device *pdev)
> +{
> +	struct ds1374_wdt *drv_data = platform_get_drvdata(pdev);
> +
> +	mutex_lock(&drv_data->mutex);
> +	ds1374_wdt_stop(drv_data->wdt);
> +	mutex_unlock(&drv_data->mutex);

Unnecessary and pointless.

> +}
> +
> +static const struct watchdog_ops ds1374_wdt_fops = {
> +	.owner          = THIS_MODULE,
> +	.start          = ds1374_wdt_start,
> +	.stop           = ds1374_wdt_stop,
> +	.ping           = ds1374_wdt_ping,
> +	.set_timeout    = ds1374_wdt_settimeout,
> +	.ioctl          = ds1374_wdt_ioctl,
> +};
> +
> +static struct watchdog_device ds1374_wdd = {
> +	.info           = &ds1374_wdt_info,
> +	.ops            = &ds1374_wdt_fops,
> +	.min_timeout    = TIMER_MARGIN_MIN,
> +	.max_timeout    = TIMER_MARGIN_MAX,

.timeout should be set here.

Also, there can (at least in theory) be more than one ds1374
in the system. The code does not support this case. ds1374_wdd
should be moved into struct ds1374_wdt.

> +};
> +
> +static struct platform_driver ds1374_wdt = {
> +	.driver         = {
> +		.owner  = THIS_MODULE,
> +		.name   = DEVNAME,
> +	},
> +	.probe          = ds1374_wdt_probe,
> +	.remove         = ds1374_wdt_remove,
> +	.shutdown       = ds1374_wdt_shutdown,
> +};
> +
> +module_platform_driver(ds1374_wdt);
> +
> +MODULE_AUTHOR("Johnson Chen <johnsonch.chen@moxa.com>");
> +MODULE_DESCRIPTION("Dallas/Maxim DS1374 Watchdog Driver");
> +MODULE_LICENSE("GPL");
> +MODULE_ALIAS("Platform:ds1374_wdt");
> 

RE: [PATCH 3/3] watchdog: ds1374_wdt: Introduce Dallas/Maxim DS1374 Watchdog driver

[Johnson CH Chen (陳昭勳)]

Hi,

Thanks for your good detailed suggestions!

> > + * It would be more efficient to use i2c msgs/i2c_transfer directly
> > +but, as
> > + * recommened in .../Documentation/i2c/writing-clients section
> > + * "Sending and receiving", using SMBus level communication is preferred.
> > + */
> > +
> > +#include <linux/kernel.h>
> > +#include <linux/device.h>
> > +#include <linux/module.h>
> > +#include <linux/ioctl.h>
> > +#include <linux/reboot.h>
> > +#include <linux/watchdog.h>
> > +#include <linux/workqueue.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/i2c.h>
> > +#include <linux/uaccess.h>
> 
> Alphabetic order please.
> 
> > +
> > +#define DEVNAME                 "ds1374_wdt"
> > +
> > +#define DS1374_REG_WDALM0	0x04 /* Watchdog/Alarm */
> > +#define DS1374_REG_WDALM1	0x05
> > +#define DS1374_REG_WDALM2	0x06
> > +#define DS1374_REG_CR		0x07 /* Control */
> > +#define DS1374_REG_CR_AIE	0x01 /* Alarm Int. Enable */
> > +#define DS1374_REG_CR_WDSTR     0x08 /* 1=INT, 0=RST */
> > +#define DS1374_REG_CR_WDALM	0x20 /* 1=Watchdog, 0=Alarm */
> > +#define DS1374_REG_CR_WACE	0x40 /* WD/Alarm counter enable */
> > +
> > +/* Default margin */
> > +#define WD_TIMO                 131762
> > +#define TIMER_MARGIN_MIN	4096 /* 1s */
> > +#define TIMER_MARGIN_MAX	(60*60*24*4096) /* one day */
> > +
> > +static int wdt_margin = WD_TIMO;
> 
> Sjould not be pre-initialized. Also, 131762 isn't 32 seconds, it is 131,762
> seconds.
> 

131762 is 32 seconds actually because watchdog counter increases per 
1/4096 seconds for DS1374. If DS1374_REG_CR_WDALM is set to 0 (alarm), 
alarm counter will increase per 1 second.

> > +module_param(wdt_margin, int, 0);
> > +MODULE_PARM_DESC(wdt_margin, "Watchdog timeout in seconds (default
> > +32s)");
> > +
> 
> As a new driver, it would be better to just use the customary "timeout".
> 
> > +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) ")");
> > +
> > +struct ds1374_wdt {
> > +	struct i2c_client *client;
> > +	struct watchdog_device *wdt;
> > +	struct work_struct work;
> 
> Not used.
> 
> > +
> > +	/* The mutex protects alarm operations, and prevents a race
> > +	 * between the enable_irq() in the workqueue and the free_irq()
> > +	 * in the remove function.
> > +	 */
> 
> There is no workqueue here, and the remove function is not needed.
> 
> > +	struct mutex mutex;
> > +};
> > +
> > +static const struct watchdog_info ds1374_wdt_info = {
> > +	.identity       = DEVNAME,
> > +	.options        = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING |
> > +						WDIOF_MAGICCLOSE,
> > +};
> > +
> > +static struct watchdog_device ds1374_wdd;
> > +
> Move declaration please.
> 
> > +static int ds1374_wdt_settimeout(struct watchdog_device *wdt,
> > +					unsigned int timeout)
> > +{
> 
> How is this synchronized against accesses by the RTC driver ?
> 
By original design in rtc-ds1374.c, it seems no synchronized problem between 
rtc and watchdog, but I think we can add mutex lock to deal with it.

> > +	int ret = -ENOIOCTLCMD;
> 
> Not an appropriate error code here.
> 
> > +	u8 buf[4];
> > +	int cr, i;
> > +	struct ds1374_wdt *drv_data = watchdog_get_drvdata(wdt);
> > +
> > +	ret = cr = i2c_smbus_read_byte_data(drv_data->client, DS1374_REG_CR);
> > +	if (ret < 0)
> > +		goto out;
> 
> "goto out;" is unnecessary. Just return the error. Same everywhere else below.
> 
> > +
> > +	/* Disable any existing watchdog/alarm before setting the new one */
> > +	cr &= ~DS1374_REG_CR_WACE;
> > +
> > +	ret = i2c_smbus_write_byte_data(drv_data->client, DS1374_REG_CR, cr);
> > +	if (ret < 0)
> > +		goto out;
> > +
> > +	/* Set new watchdog time */
> > +	for (i = 0; i < 3; i++) {
> > +		buf[i] = timeout & 0xff;
> > +		timeout >>= 8;
> > +	}
> 
> The value passed to this function from the watchdog core is the timeout in
> seconds. I don't see a conversion to internal values here.
> 

For original design in rtc-ds1374.c, ds1374_wdt_settimeout () will call 
ds1374_write_rtc() to write hardware register. To separate watchdog and rtc 
functions, expand code from ds1374_write_rtc() here, and final buf[] values 
will be written into hardware register for DS1374.

> > +
> > +	ret = i2c_smbus_write_i2c_block_data(drv_data->client,
> > +						DS1374_REG_WDALM0, 3, buf);
> > +	if (ret) {
> > +		pr_info("couldn't set new watchdog time\n");
> > +		goto out;
> > +	}
> 
> > +
> > +	/* Enable watchdog timer */
> > +	cr |= DS1374_REG_CR_WACE | DS1374_REG_CR_WDALM;
> > +	cr &= ~DS1374_REG_CR_WDSTR;/* for RST PIN */
> > +	cr &= ~DS1374_REG_CR_AIE;
> > +
> > +	ret = i2c_smbus_write_byte_data(drv_data->client, DS1374_REG_CR, cr);
> > +	if (ret < 0)
> > +		goto out;
> > +
> > +	return 0;
> 
> Pointless. Just return ret.
> 
> Also, this function needs to store the new timeout in struct watchdog_device.
> 
> > +out:
> > +	return ret;
> > +}
> > +
> > +
> > +/*
> > + * Read WD/Alarm counter to reload the watchdog timer. (ie, pat the
> > +watchdog)  */ static int ds1374_wdt_ping(struct watchdog_device *wdt)
> > +{
> > +	struct ds1374_wdt *drv_data = watchdog_get_drvdata(wdt);
> > +	int ret;
> > +	u8 buf[4];
> > +
> > +	ret = i2c_smbus_read_i2c_block_data(drv_data->client,
> > +						DS1374_REG_WDALM0, 3, buf);
> > +
> > +	if (ret < 0 || ret < 3)
> > +		pr_info("WD TICK FAIL!!!!!!!!!! %i\n", ret);
> > +
> 
> This is not an info message, this is an error. Besides, it is just noise.
> Just return the error and drop the message.
> 
> > +	return ret;
> > +}
> > +
> > +static int ds1374_wdt_start(struct watchdog_device *wdt) {
> > +	int ret;
> > +
> > +	ret = ds1374_wdt_settimeout(wdt, wdt_margin);
> 
> This is wrong. The timeout may have been updated by userspace.
> It is inappropriate to change it back to the default here.
> 
Thanks, I will keep in mind.

> > +	if (ret)
> > +		return ret;
> > +
> > +	ds1374_wdt_ping(wdt);
> 
> Please do not ignore errors.
> 
> > +
> > +	return 0;
> > +}
> > +
> > +static int ds1374_wdt_stop(struct watchdog_device *wdt) {
> > +	struct ds1374_wdt *drv_data = watchdog_get_drvdata(wdt);
> > +	int cr;
> > +
> > +	if (nowayout)
> > +		return 0;
> 
> Not needed.
> 
Thanks!, it has been implemented in watchdog_stop().

> > +
> > +	cr = i2c_smbus_read_byte_data(drv_data->client, DS1374_REG_CR);
> > +	/* Disable watchdog timer */
> > +	cr &= ~DS1374_REG_CR_WACE;
> > +
> > +	return i2c_smbus_write_byte_data(drv_data->client, DS1374_REG_CR,
> > +cr); }
> > +
> > +/*
> > + * Handle commands from user-space.
> > + */
> > +static long ds1374_wdt_ioctl(struct watchdog_device *wdt, unsigned int
> cmd,
> > +				unsigned long arg)
> 
> The whole point of using the watchdog subsystem is to not need a local ioctl
> function - and most definitely not one that duplicates watchdog core
> functionality.
> 
> > +{
> > +	int new_margin, options;
> > +
> > +	switch (cmd) {
> > +	case WDIOC_GETSUPPORT:
> > +		return copy_to_user((struct watchdog_info __user *)arg,
> > +		&ds1374_wdt_info, sizeof(ds1374_wdt_info)) ? -EFAULT : 0;
> > +
> > +	case WDIOC_GETSTATUS:
> > +	case WDIOC_GETBOOTSTATUS:
> > +		return put_user(0, (int __user *)arg);
> > +	case WDIOC_KEEPALIVE:
> > +		ds1374_wdt_ping(wdt);
> > +		return 0;
> > +	case WDIOC_SETTIMEOUT:
> > +		if (get_user(new_margin, (int __user *)arg))
> > +			return -EFAULT;
> > +
> > +		/* the hardware's tick rate is 4096 Hz, so
> > +		 * the counter value needs to be scaled accordingly
> > +		 */
> > +		new_margin <<= 12;
> > +		if (new_margin < 1 || new_margin > 16777216)
> > +			return -EINVAL;
> > +
> > +		wdt_margin = new_margin;
> > +		ds1374_wdt_settimeout(wdt, new_margin);
> 
> Is the idea here to bypass the watchdog subsystem's notion of keeping the
> timeout in seconds ? If so, that would be wrong and unacceptable.
> 
It seems take care about 4096Hz for original design in rtc-ds1374.c. I think we
can just use ioctl() which watchdog core provides and input margin time
appropriately.


> > +		ds1374_wdt_ping(wdt);
> > +		fallthrough;
> > +	case WDIOC_GETTIMEOUT:
> > +		/* when returning ... inverse is true */
> > +		return put_user((wdt_margin >> 12), (int __user *)arg);
> > +	case WDIOC_SETOPTIONS:
> > +		if (copy_from_user(&options, (int __user *)arg, sizeof(int)))
> > +			return -EFAULT;
> > +
> > +		if (options & WDIOS_DISABLECARD) {
> > +			pr_info("disable watchdog\n");
> > +			ds1374_wdt_stop(wdt);
> > +			return 0;
> > +		}
> > +
> > +		if (options & WDIOS_ENABLECARD) {
> > +			pr_info("enable watchdog\n");
> > +			ds1374_wdt_settimeout(wdt, wdt_margin);
> > +			ds1374_wdt_ping(wdt);
> > +			return 0;
> > +		}
> > +		return -EINVAL;
> > +	}
> > +	return -ENOTTY;
> > +}
> > +
> > +static int ds1374_wdt_notify_sys(struct notifier_block *this,
> > +			unsigned long code, void *unused)
> > +{
> > +	if (code == SYS_DOWN || code == SYS_HALT)
> > +		/* Disable Watchdog */
> > +		ds1374_wdt_stop(&ds1374_wdd);
> > +	return NOTIFY_DONE;
> > +}
> > +
> Not needed - see below.
> 
> > +static struct notifier_block ds1374_wdt_notifier = {
> > +	.notifier_call = ds1374_wdt_notify_sys, };
> > +
> > +static int ds1374_wdt_probe(struct platform_device *pdev) {
> > +	struct ds1374_wdt *drv_data;
> > +	struct i2c_client *client = to_i2c_client(pdev->dev.parent);
> > +	int ret;
> > +
> > +	drv_data = devm_kzalloc(&pdev->dev, sizeof(struct ds1374_wdt),
> > +				GFP_KERNEL);
> > +	if (!drv_data)
> > +		return -ENOMEM;
> > +
> > +	drv_data->wdt = &ds1374_wdd;
> > +	drv_data->client = client;
> > +	mutex_init(&drv_data->mutex);
> > +
> > +	watchdog_init_timeout(drv_data->wdt, wdt_margin, &pdev->dev);
> > +	watchdog_set_nowayout(drv_data->wdt, nowayout);
> > +
> > +	watchdog_set_drvdata(drv_data->wdt, drv_data);
> > +	platform_set_drvdata(pdev, drv_data);
> > +
> > +	ret = watchdog_register_device(drv_data->wdt);
> 
> Use devm_watchdog_register_device()
> 
> > +	if (ret) {
> > +		dev_err(&pdev->dev, "failed to register Watchdog device\n");
> > +		return ret;
> > +	}
> > +
> > +	ret = register_reboot_notifier(&ds1374_wdt_notifier);
> 
> Call watchdog_stop_on_reboot() before calling watchdog_register_device()
> instead.
> 
> > +	if (ret) {
> > +		watchdog_unregister_device(drv_data->wdt);
> > +		return ret;
> > +	}
> > +
> > +	ds1374_wdt_settimeout(drv_data->wdt, wdt_margin);
> 
> Unnecessary here; called from start function.
> 
> > +	dev_info(&pdev->dev, "Dallas/Maxim DS1374 watchdog device
> > +enabled\n");
> > +
> > +	return 0;
> > +}
> > +
> > +static int ds1374_wdt_remove(struct platform_device *pdev) {
> > +	struct ds1374_wdt *drv_data = platform_get_drvdata(pdev);
> > +
> > +	dev_warn(&pdev->dev, "Unregister DS1374 watchdog device\n");
> > +	watchdog_unregister_device(drv_data->wdt);
> > +	unregister_reboot_notifier(&ds1374_wdt_notifier);
> > +
> 
> Call watchdog_stop_on_unregister() before calling
> watchdog_register_device().
> 
> > +	return 0;
> > +}
> > +
> > +static void ds1374_wdt_shutdown(struct platform_device *pdev) {
> > +	struct ds1374_wdt *drv_data = platform_get_drvdata(pdev);
> > +
> > +	mutex_lock(&drv_data->mutex);
> > +	ds1374_wdt_stop(drv_data->wdt);
> > +	mutex_unlock(&drv_data->mutex);
> 
> Unnecessary and pointless.
> 
> > +}
> > +
> > +static const struct watchdog_ops ds1374_wdt_fops = {
> > +	.owner          = THIS_MODULE,
> > +	.start          = ds1374_wdt_start,
> > +	.stop           = ds1374_wdt_stop,
> > +	.ping           = ds1374_wdt_ping,
> > +	.set_timeout    = ds1374_wdt_settimeout,
> > +	.ioctl          = ds1374_wdt_ioctl,
> > +};
> > +
> > +static struct watchdog_device ds1374_wdd = {
> > +	.info           = &ds1374_wdt_info,
> > +	.ops            = &ds1374_wdt_fops,
> > +	.min_timeout    = TIMER_MARGIN_MIN,
> > +	.max_timeout    = TIMER_MARGIN_MAX,
> 
> .timeout should be set here.
> 
> Also, there can (at least in theory) be more than one ds1374 in the system. The
> code does not support this case. ds1374_wdd should be moved into struct
> ds1374_wdt.
> 
Thanks for good suggestion.
> > +};
> > +
> > +static struct platform_driver ds1374_wdt = {
> > +	.driver         = {
> > +		.owner  = THIS_MODULE,
> > +		.name   = DEVNAME,
> > +	},
> > +	.probe          = ds1374_wdt_probe,
> > +	.remove         = ds1374_wdt_remove,
> > +	.shutdown       = ds1374_wdt_shutdown,
> > +};
> > +
> > +module_platform_driver(ds1374_wdt);
> > +
> > +MODULE_AUTHOR("Johnson Chen <johnsonch.chen@moxa.com>");
> > +MODULE_DESCRIPTION("Dallas/Maxim DS1374 Watchdog Driver");
> > +MODULE_LICENSE("GPL"); MODULE_ALIAS("Platform:ds1374_wdt");
> >

Best regards,
Johnson

Re: [PATCH 3/3] watchdog: ds1374_wdt: Introduce Dallas/Maxim DS1374 Watchdog driver

[Guenter Roeck]

On 6/22/20 11:28 PM, Johnson CH Chen (陳昭勳) wrote:
> Hi,
> 
> Thanks for your good detailed suggestions!
> 

Other feedback suggests to convert the driver to use
the watchdog core in the rtc code. I would suggest to follow
that suggestion.

>>> + * It would be more efficient to use i2c msgs/i2c_transfer directly
>>> +but, as
>>> + * recommened in .../Documentation/i2c/writing-clients section
>>> + * "Sending and receiving", using SMBus level communication is preferred.
>>> + */
>>> +
>>> +#include <linux/kernel.h>
>>> +#include <linux/device.h>
>>> +#include <linux/module.h>
>>> +#include <linux/ioctl.h>
>>> +#include <linux/reboot.h>
>>> +#include <linux/watchdog.h>
>>> +#include <linux/workqueue.h>
>>> +#include <linux/platform_device.h>
>>> +#include <linux/i2c.h>
>>> +#include <linux/uaccess.h>
>>
>> Alphabetic order please.
>>
>>> +
>>> +#define DEVNAME                 "ds1374_wdt"
>>> +
>>> +#define DS1374_REG_WDALM0	0x04 /* Watchdog/Alarm */
>>> +#define DS1374_REG_WDALM1	0x05
>>> +#define DS1374_REG_WDALM2	0x06
>>> +#define DS1374_REG_CR		0x07 /* Control */
>>> +#define DS1374_REG_CR_AIE	0x01 /* Alarm Int. Enable */
>>> +#define DS1374_REG_CR_WDSTR     0x08 /* 1=INT, 0=RST */
>>> +#define DS1374_REG_CR_WDALM	0x20 /* 1=Watchdog, 0=Alarm */
>>> +#define DS1374_REG_CR_WACE	0x40 /* WD/Alarm counter enable */
>>> +
>>> +/* Default margin */
>>> +#define WD_TIMO                 131762
>>> +#define TIMER_MARGIN_MIN	4096 /* 1s */
>>> +#define TIMER_MARGIN_MAX	(60*60*24*4096) /* one day */
>>> +
>>> +static int wdt_margin = WD_TIMO;
>>
>> Sjould not be pre-initialized. Also, 131762 isn't 32 seconds, it is 131,762
>> seconds.
>>
> 
> 131762 is 32 seconds actually because watchdog counter increases per 
> 1/4096 seconds for DS1374. If DS1374_REG_CR_WDALM is set to 0 (alarm), 
> alarm counter will increase per 1 second.
> 

The watchdog core keeps timeouts in seconds. For the watchdog core,
131762 is 131,762 seconds. Your code assumes that the watchdog core
does not care about / need to scale, which is wrong. Besides,
MODULE_PARM_DESC below clearly states "Watchdog timeout _in seconds_"
(emphasis added).

>>> +module_param(wdt_margin, int, 0);
>>> +MODULE_PARM_DESC(wdt_margin, "Watchdog timeout in seconds (default
>>> +32s)");
>>> +
>>
>> As a new driver, it would be better to just use the customary "timeout".
>>
>>> +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) ")");
>>> +
>>> +struct ds1374_wdt {
>>> +	struct i2c_client *client;
>>> +	struct watchdog_device *wdt;
>>> +	struct work_struct work;
>>
>> Not used.
>>
>>> +
>>> +	/* The mutex protects alarm operations, and prevents a race
>>> +	 * between the enable_irq() in the workqueue and the free_irq()
>>> +	 * in the remove function.
>>> +	 */
>>
>> There is no workqueue here, and the remove function is not needed.
>>
>>> +	struct mutex mutex;
>>> +};
>>> +
>>> +static const struct watchdog_info ds1374_wdt_info = {
>>> +	.identity       = DEVNAME,
>>> +	.options        = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING |
>>> +						WDIOF_MAGICCLOSE,
>>> +};
>>> +
>>> +static struct watchdog_device ds1374_wdd;
>>> +
>> Move declaration please.
>>
>>> +static int ds1374_wdt_settimeout(struct watchdog_device *wdt,
>>> +					unsigned int timeout)
>>> +{
>>
>> How is this synchronized against accesses by the RTC driver ?
>>
> By original design in rtc-ds1374.c, it seems no synchronized problem between 
> rtc and watchdog, but I think we can add mutex lock to deal with it.
> 
The mutex is used there where needed.

>>> +	int ret = -ENOIOCTLCMD;
>>
>> Not an appropriate error code here.
>>
>>> +	u8 buf[4];
>>> +	int cr, i;
>>> +	struct ds1374_wdt *drv_data = watchdog_get_drvdata(wdt);
>>> +
>>> +	ret = cr = i2c_smbus_read_byte_data(drv_data->client, DS1374_REG_CR);
>>> +	if (ret < 0)
>>> +		goto out;
>>
>> "goto out;" is unnecessary. Just return the error. Same everywhere else below.
>>
>>> +
>>> +	/* Disable any existing watchdog/alarm before setting the new one */
>>> +	cr &= ~DS1374_REG_CR_WACE;
>>> +
>>> +	ret = i2c_smbus_write_byte_data(drv_data->client, DS1374_REG_CR, cr);
>>> +	if (ret < 0)
>>> +		goto out;
>>> +
>>> +	/* Set new watchdog time */
>>> +	for (i = 0; i < 3; i++) {
>>> +		buf[i] = timeout & 0xff;
>>> +		timeout >>= 8;
>>> +	}
>>
>> The value passed to this function from the watchdog core is the timeout in
>> seconds. I don't see a conversion to internal values here.
>>
> 
> For original design in rtc-ds1374.c, ds1374_wdt_settimeout () will call 
> ds1374_write_rtc() to write hardware register. To separate watchdog and rtc 
> functions, expand code from ds1374_write_rtc() here, and final buf[] values 
> will be written into hardware register for DS1374.
> 

ds1374_wdt_settimeout() is an API function, It gets timeouts from the watchdog
core in seconds. Those timeouts have to be converted to chip internal values
in this function.

>>> +
>>> +	ret = i2c_smbus_write_i2c_block_data(drv_data->client,
>>> +						DS1374_REG_WDALM0, 3, buf);
>>> +	if (ret) {
>>> +		pr_info("couldn't set new watchdog time\n");
>>> +		goto out;
>>> +	}
>>
>>> +
>>> +	/* Enable watchdog timer */
>>> +	cr |= DS1374_REG_CR_WACE | DS1374_REG_CR_WDALM;
>>> +	cr &= ~DS1374_REG_CR_WDSTR;/* for RST PIN */
>>> +	cr &= ~DS1374_REG_CR_AIE;
>>> +
>>> +	ret = i2c_smbus_write_byte_data(drv_data->client, DS1374_REG_CR, cr);
>>> +	if (ret < 0)
>>> +		goto out;
>>> +
>>> +	return 0;
>>
>> Pointless. Just return ret.
>>
>> Also, this function needs to store the new timeout in struct watchdog_device.
>>
>>> +out:
>>> +	return ret;
>>> +}
>>> +
>>> +
>>> +/*
>>> + * Read WD/Alarm counter to reload the watchdog timer. (ie, pat the
>>> +watchdog)  */ static int ds1374_wdt_ping(struct watchdog_device *wdt)
>>> +{
>>> +	struct ds1374_wdt *drv_data = watchdog_get_drvdata(wdt);
>>> +	int ret;
>>> +	u8 buf[4];
>>> +
>>> +	ret = i2c_smbus_read_i2c_block_data(drv_data->client,
>>> +						DS1374_REG_WDALM0, 3, buf);
>>> +
>>> +	if (ret < 0 || ret < 3)
>>> +		pr_info("WD TICK FAIL!!!!!!!!!! %i\n", ret);
>>> +
>>
>> This is not an info message, this is an error. Besides, it is just noise.
>> Just return the error and drop the message.
>>
>>> +	return ret;
>>> +}
>>> +
>>> +static int ds1374_wdt_start(struct watchdog_device *wdt) {
>>> +	int ret;
>>> +
>>> +	ret = ds1374_wdt_settimeout(wdt, wdt_margin);
>>
>> This is wrong. The timeout may have been updated by userspace.
>> It is inappropriate to change it back to the default here.
>>
> Thanks, I will keep in mind.
> 
>>> +	if (ret)
>>> +		return ret;
>>> +
>>> +	ds1374_wdt_ping(wdt);
>>
>> Please do not ignore errors.
>>
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static int ds1374_wdt_stop(struct watchdog_device *wdt) {
>>> +	struct ds1374_wdt *drv_data = watchdog_get_drvdata(wdt);
>>> +	int cr;
>>> +
>>> +	if (nowayout)
>>> +		return 0;
>>
>> Not needed.
>>
> Thanks!, it has been implemented in watchdog_stop().
> 
>>> +
>>> +	cr = i2c_smbus_read_byte_data(drv_data->client, DS1374_REG_CR);
>>> +	/* Disable watchdog timer */
>>> +	cr &= ~DS1374_REG_CR_WACE;
>>> +
>>> +	return i2c_smbus_write_byte_data(drv_data->client, DS1374_REG_CR,
>>> +cr); }
>>> +
>>> +/*
>>> + * Handle commands from user-space.
>>> + */
>>> +static long ds1374_wdt_ioctl(struct watchdog_device *wdt, unsigned int
>> cmd,
>>> +				unsigned long arg)
>>
>> The whole point of using the watchdog subsystem is to not need a local ioctl
>> function - and most definitely not one that duplicates watchdog core
>> functionality.
>>
>>> +{
>>> +	int new_margin, options;
>>> +
>>> +	switch (cmd) {
>>> +	case WDIOC_GETSUPPORT:
>>> +		return copy_to_user((struct watchdog_info __user *)arg,
>>> +		&ds1374_wdt_info, sizeof(ds1374_wdt_info)) ? -EFAULT : 0;
>>> +
>>> +	case WDIOC_GETSTATUS:
>>> +	case WDIOC_GETBOOTSTATUS:
>>> +		return put_user(0, (int __user *)arg);
>>> +	case WDIOC_KEEPALIVE:
>>> +		ds1374_wdt_ping(wdt);
>>> +		return 0;
>>> +	case WDIOC_SETTIMEOUT:
>>> +		if (get_user(new_margin, (int __user *)arg))
>>> +			return -EFAULT;
>>> +
>>> +		/* the hardware's tick rate is 4096 Hz, so
>>> +		 * the counter value needs to be scaled accordingly
>>> +		 */
>>> +		new_margin <<= 12;
>>> +		if (new_margin < 1 || new_margin > 16777216)
>>> +			return -EINVAL;
>>> +
>>> +		wdt_margin = new_margin;
>>> +		ds1374_wdt_settimeout(wdt, new_margin);
>>
>> Is the idea here to bypass the watchdog subsystem's notion of keeping the
>> timeout in seconds ? If so, that would be wrong and unacceptable.
>>
> It seems take care about 4096Hz for original design in rtc-ds1374.c. I think we
> can just use ioctl() which watchdog core provides and input margin time
> appropriately.
> 
> 
>>> +		ds1374_wdt_ping(wdt);
>>> +		fallthrough;
>>> +	case WDIOC_GETTIMEOUT:
>>> +		/* when returning ... inverse is true */
>>> +		return put_user((wdt_margin >> 12), (int __user *)arg);
>>> +	case WDIOC_SETOPTIONS:
>>> +		if (copy_from_user(&options, (int __user *)arg, sizeof(int)))
>>> +			return -EFAULT;
>>> +
>>> +		if (options & WDIOS_DISABLECARD) {
>>> +			pr_info("disable watchdog\n");
>>> +			ds1374_wdt_stop(wdt);
>>> +			return 0;
>>> +		}
>>> +
>>> +		if (options & WDIOS_ENABLECARD) {
>>> +			pr_info("enable watchdog\n");
>>> +			ds1374_wdt_settimeout(wdt, wdt_margin);
>>> +			ds1374_wdt_ping(wdt);
>>> +			return 0;
>>> +		}
>>> +		return -EINVAL;
>>> +	}
>>> +	return -ENOTTY;
>>> +}
>>> +
>>> +static int ds1374_wdt_notify_sys(struct notifier_block *this,
>>> +			unsigned long code, void *unused)
>>> +{
>>> +	if (code == SYS_DOWN || code == SYS_HALT)
>>> +		/* Disable Watchdog */
>>> +		ds1374_wdt_stop(&ds1374_wdd);
>>> +	return NOTIFY_DONE;
>>> +}
>>> +
>> Not needed - see below.
>>
>>> +static struct notifier_block ds1374_wdt_notifier = {
>>> +	.notifier_call = ds1374_wdt_notify_sys, };
>>> +
>>> +static int ds1374_wdt_probe(struct platform_device *pdev) {
>>> +	struct ds1374_wdt *drv_data;
>>> +	struct i2c_client *client = to_i2c_client(pdev->dev.parent);
>>> +	int ret;
>>> +
>>> +	drv_data = devm_kzalloc(&pdev->dev, sizeof(struct ds1374_wdt),
>>> +				GFP_KERNEL);
>>> +	if (!drv_data)
>>> +		return -ENOMEM;
>>> +
>>> +	drv_data->wdt = &ds1374_wdd;
>>> +	drv_data->client = client;
>>> +	mutex_init(&drv_data->mutex);
>>> +
>>> +	watchdog_init_timeout(drv_data->wdt, wdt_margin, &pdev->dev);
>>> +	watchdog_set_nowayout(drv_data->wdt, nowayout);
>>> +
>>> +	watchdog_set_drvdata(drv_data->wdt, drv_data);
>>> +	platform_set_drvdata(pdev, drv_data);
>>> +
>>> +	ret = watchdog_register_device(drv_data->wdt);
>>
>> Use devm_watchdog_register_device()
>>
>>> +	if (ret) {
>>> +		dev_err(&pdev->dev, "failed to register Watchdog device\n");
>>> +		return ret;
>>> +	}
>>> +
>>> +	ret = register_reboot_notifier(&ds1374_wdt_notifier);
>>
>> Call watchdog_stop_on_reboot() before calling watchdog_register_device()
>> instead.
>>
>>> +	if (ret) {
>>> +		watchdog_unregister_device(drv_data->wdt);
>>> +		return ret;
>>> +	}
>>> +
>>> +	ds1374_wdt_settimeout(drv_data->wdt, wdt_margin);
>>
>> Unnecessary here; called from start function.
>>
>>> +	dev_info(&pdev->dev, "Dallas/Maxim DS1374 watchdog device
>>> +enabled\n");
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static int ds1374_wdt_remove(struct platform_device *pdev) {
>>> +	struct ds1374_wdt *drv_data = platform_get_drvdata(pdev);
>>> +
>>> +	dev_warn(&pdev->dev, "Unregister DS1374 watchdog device\n");
>>> +	watchdog_unregister_device(drv_data->wdt);
>>> +	unregister_reboot_notifier(&ds1374_wdt_notifier);
>>> +
>>
>> Call watchdog_stop_on_unregister() before calling
>> watchdog_register_device().
>>
>>> +	return 0;
>>> +}
>>> +
>>> +static void ds1374_wdt_shutdown(struct platform_device *pdev) {
>>> +	struct ds1374_wdt *drv_data = platform_get_drvdata(pdev);
>>> +
>>> +	mutex_lock(&drv_data->mutex);
>>> +	ds1374_wdt_stop(drv_data->wdt);
>>> +	mutex_unlock(&drv_data->mutex);
>>
>> Unnecessary and pointless.
>>
>>> +}
>>> +
>>> +static const struct watchdog_ops ds1374_wdt_fops = {
>>> +	.owner          = THIS_MODULE,
>>> +	.start          = ds1374_wdt_start,
>>> +	.stop           = ds1374_wdt_stop,
>>> +	.ping           = ds1374_wdt_ping,
>>> +	.set_timeout    = ds1374_wdt_settimeout,
>>> +	.ioctl          = ds1374_wdt_ioctl,
>>> +};
>>> +
>>> +static struct watchdog_device ds1374_wdd = {
>>> +	.info           = &ds1374_wdt_info,
>>> +	.ops            = &ds1374_wdt_fops,
>>> +	.min_timeout    = TIMER_MARGIN_MIN,
>>> +	.max_timeout    = TIMER_MARGIN_MAX,
>>
>> .timeout should be set here.
>>
>> Also, there can (at least in theory) be more than one ds1374 in the system. The
>> code does not support this case. ds1374_wdd should be moved into struct
>> ds1374_wdt.
>>
> Thanks for good suggestion.
>>> +};
>>> +
>>> +static struct platform_driver ds1374_wdt = {
>>> +	.driver         = {
>>> +		.owner  = THIS_MODULE,
>>> +		.name   = DEVNAME,
>>> +	},
>>> +	.probe          = ds1374_wdt_probe,
>>> +	.remove         = ds1374_wdt_remove,
>>> +	.shutdown       = ds1374_wdt_shutdown,
>>> +};
>>> +
>>> +module_platform_driver(ds1374_wdt);
>>> +
>>> +MODULE_AUTHOR("Johnson Chen <johnsonch.chen@moxa.com>");
>>> +MODULE_DESCRIPTION("Dallas/Maxim DS1374 Watchdog Driver");
>>> +MODULE_LICENSE("GPL"); MODULE_ALIAS("Platform:ds1374_wdt");
>>>
> 
> Best regards,
> Johnson
> 

RE: [PATCH 3/3] watchdog: ds1374_wdt: Introduce Dallas/Maxim DS1374 Watchdog driver

[Johnson CH Chen (陳昭勳)]

Hi,

> On 6/22/20 11:28 PM, Johnson CH Chen (陳昭勳) wrote:
> > Hi,
> >
> > Thanks for your good detailed suggestions!
> >
> 
> Other feedback suggests to convert the driver to use the watchdog core in the
> rtc code. I would suggest to follow that suggestion.
> 
Understand the following suggestions for watchdog timer setting and I will improve them with watchdog core in rtc code later.


Best regards,
Johnson

> >>> + * It would be more efficient to use i2c msgs/i2c_transfer directly
> >>> +but, as
> >>> + * recommened in .../Documentation/i2c/writing-clients section
> >>> + * "Sending and receiving", using SMBus level communication is
> preferred.
> >>> + */
> >>> +
> >>> +#include <linux/kernel.h>
> >>> +#include <linux/device.h>
> >>> +#include <linux/module.h>
> >>> +#include <linux/ioctl.h>
> >>> +#include <linux/reboot.h>
> >>> +#include <linux/watchdog.h>
> >>> +#include <linux/workqueue.h>
> >>> +#include <linux/platform_device.h>
> >>> +#include <linux/i2c.h>
> >>> +#include <linux/uaccess.h>
> >>
> >> Alphabetic order please.
> >>
> >>> +
> >>> +#define DEVNAME                 "ds1374_wdt"
> >>> +
> >>> +#define DS1374_REG_WDALM0	0x04 /* Watchdog/Alarm */
> >>> +#define DS1374_REG_WDALM1	0x05
> >>> +#define DS1374_REG_WDALM2	0x06
> >>> +#define DS1374_REG_CR		0x07 /* Control */
> >>> +#define DS1374_REG_CR_AIE	0x01 /* Alarm Int. Enable */
> >>> +#define DS1374_REG_CR_WDSTR     0x08 /* 1=INT, 0=RST */
> >>> +#define DS1374_REG_CR_WDALM	0x20 /* 1=Watchdog, 0=Alarm */
> >>> +#define DS1374_REG_CR_WACE	0x40 /* WD/Alarm counter enable */
> >>> +
> >>> +/* Default margin */
> >>> +#define WD_TIMO                 131762
> >>> +#define TIMER_MARGIN_MIN	4096 /* 1s */
> >>> +#define TIMER_MARGIN_MAX	(60*60*24*4096) /* one day */
> >>> +
> >>> +static int wdt_margin = WD_TIMO;
> >>
> >> Sjould not be pre-initialized. Also, 131762 isn't 32 seconds, it is
> >> 131,762 seconds.
> >>
> >
> > 131762 is 32 seconds actually because watchdog counter increases per
> > 1/4096 seconds for DS1374. If DS1374_REG_CR_WDALM is set to 0 (alarm),
> > alarm counter will increase per 1 second.
> >
> 
> The watchdog core keeps timeouts in seconds. For the watchdog core,
> 131762 is 131,762 seconds. Your code assumes that the watchdog core
> does not care about / need to scale, which is wrong. Besides,
> MODULE_PARM_DESC below clearly states "Watchdog timeout _in seconds_"
> (emphasis added).
> 
> >>> +module_param(wdt_margin, int, 0);
> >>> +MODULE_PARM_DESC(wdt_margin, "Watchdog timeout in seconds
> (default
> >>> +32s)");
> >>> +
> >>
> >> As a new driver, it would be better to just use the customary "timeout".
> >>
> >>> +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) ")");
> >>> +
> >>> +struct ds1374_wdt {
> >>> +	struct i2c_client *client;
> >>> +	struct watchdog_device *wdt;
> >>> +	struct work_struct work;
> >>
> >> Not used.
> >>
> >>> +
> >>> +	/* The mutex protects alarm operations, and prevents a race
> >>> +	 * between the enable_irq() in the workqueue and the free_irq()
> >>> +	 * in the remove function.
> >>> +	 */
> >>
> >> There is no workqueue here, and the remove function is not needed.
> >>
> >>> +	struct mutex mutex;
> >>> +};
> >>> +
> >>> +static const struct watchdog_info ds1374_wdt_info = {
> >>> +	.identity       = DEVNAME,
> >>> +	.options        = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING |
> >>> +						WDIOF_MAGICCLOSE,
> >>> +};
> >>> +
> >>> +static struct watchdog_device ds1374_wdd;
> >>> +
> >> Move declaration please.
> >>
> >>> +static int ds1374_wdt_settimeout(struct watchdog_device *wdt,
> >>> +					unsigned int timeout)
> >>> +{
> >>
> >> How is this synchronized against accesses by the RTC driver ?
> >>
> > By original design in rtc-ds1374.c, it seems no synchronized problem
> between
> > rtc and watchdog, but I think we can add mutex lock to deal with it.
> >
> The mutex is used there where needed.
> 
> >>> +	int ret = -ENOIOCTLCMD;
> >>
> >> Not an appropriate error code here.
> >>
> >>> +	u8 buf[4];
> >>> +	int cr, i;
> >>> +	struct ds1374_wdt *drv_data = watchdog_get_drvdata(wdt);
> >>> +
> >>> +	ret = cr = i2c_smbus_read_byte_data(drv_data->client,
> DS1374_REG_CR);
> >>> +	if (ret < 0)
> >>> +		goto out;
> >>
> >> "goto out;" is unnecessary. Just return the error. Same everywhere else
> below.
> >>
> >>> +
> >>> +	/* Disable any existing watchdog/alarm before setting the new one
> */
> >>> +	cr &= ~DS1374_REG_CR_WACE;
> >>> +
> >>> +	ret = i2c_smbus_write_byte_data(drv_data->client, DS1374_REG_CR,
> cr);
> >>> +	if (ret < 0)
> >>> +		goto out;
> >>> +
> >>> +	/* Set new watchdog time */
> >>> +	for (i = 0; i < 3; i++) {
> >>> +		buf[i] = timeout & 0xff;
> >>> +		timeout >>= 8;
> >>> +	}
> >>
> >> The value passed to this function from the watchdog core is the timeout in
> >> seconds. I don't see a conversion to internal values here.
> >>
> >
> > For original design in rtc-ds1374.c, ds1374_wdt_settimeout () will call
> > ds1374_write_rtc() to write hardware register. To separate watchdog and rtc
> > functions, expand code from ds1374_write_rtc() here, and final buf[] values
> > will be written into hardware register for DS1374.
> >
> 
> ds1374_wdt_settimeout() is an API function, It gets timeouts from the
> watchdog
> core in seconds. Those timeouts have to be converted to chip internal values
> in this function.
> 
> >>> +
> >>> +	ret = i2c_smbus_write_i2c_block_data(drv_data->client,
> >>> +						DS1374_REG_WDALM0, 3, buf);
> >>> +	if (ret) {
> >>> +		pr_info("couldn't set new watchdog time\n");
> >>> +		goto out;
> >>> +	}
> >>
> >>> +
> >>> +	/* Enable watchdog timer */
> >>> +	cr |= DS1374_REG_CR_WACE | DS1374_REG_CR_WDALM;
> >>> +	cr &= ~DS1374_REG_CR_WDSTR;/* for RST PIN */
> >>> +	cr &= ~DS1374_REG_CR_AIE;
> >>> +
> >>> +	ret = i2c_smbus_write_byte_data(drv_data->client, DS1374_REG_CR,
> cr);
> >>> +	if (ret < 0)
> >>> +		goto out;
> >>> +
> >>> +	return 0;
> >>
> >> Pointless. Just return ret.
> >>
> >> Also, this function needs to store the new timeout in struct
> watchdog_device.
> >>
> >>> +out:
> >>> +	return ret;
> >>> +}
> >>> +
> >>> +
> >>> +/*
> >>> + * Read WD/Alarm counter to reload the watchdog timer. (ie, pat the
> >>> +watchdog)  */ static int ds1374_wdt_ping(struct watchdog_device *wdt)
> >>> +{
> >>> +	struct ds1374_wdt *drv_data = watchdog_get_drvdata(wdt);
> >>> +	int ret;
> >>> +	u8 buf[4];
> >>> +
> >>> +	ret = i2c_smbus_read_i2c_block_data(drv_data->client,
> >>> +						DS1374_REG_WDALM0, 3, buf);
> >>> +
> >>> +	if (ret < 0 || ret < 3)
> >>> +		pr_info("WD TICK FAIL!!!!!!!!!! %i\n", ret);
> >>> +
> >>
> >> This is not an info message, this is an error. Besides, it is just noise.
> >> Just return the error and drop the message.
> >>
> >>> +	return ret;
> >>> +}
> >>> +
> >>> +static int ds1374_wdt_start(struct watchdog_device *wdt) {
> >>> +	int ret;
> >>> +
> >>> +	ret = ds1374_wdt_settimeout(wdt, wdt_margin);
> >>
> >> This is wrong. The timeout may have been updated by userspace.
> >> It is inappropriate to change it back to the default here.
> >>
> > Thanks, I will keep in mind.
> >
> >>> +	if (ret)
> >>> +		return ret;
> >>> +
> >>> +	ds1374_wdt_ping(wdt);
> >>
> >> Please do not ignore errors.
> >>
> >>> +
> >>> +	return 0;
> >>> +}
> >>> +
> >>> +static int ds1374_wdt_stop(struct watchdog_device *wdt) {
> >>> +	struct ds1374_wdt *drv_data = watchdog_get_drvdata(wdt);
> >>> +	int cr;
> >>> +
> >>> +	if (nowayout)
> >>> +		return 0;
> >>
> >> Not needed.
> >>
> > Thanks!, it has been implemented in watchdog_stop().
> >
> >>> +
> >>> +	cr = i2c_smbus_read_byte_data(drv_data->client, DS1374_REG_CR);
> >>> +	/* Disable watchdog timer */
> >>> +	cr &= ~DS1374_REG_CR_WACE;
> >>> +
> >>> +	return i2c_smbus_write_byte_data(drv_data->client,
> DS1374_REG_CR,
> >>> +cr); }
> >>> +
> >>> +/*
> >>> + * Handle commands from user-space.
> >>> + */
> >>> +static long ds1374_wdt_ioctl(struct watchdog_device *wdt, unsigned int
> >> cmd,
> >>> +				unsigned long arg)
> >>
> >> The whole point of using the watchdog subsystem is to not need a local ioctl
> >> function - and most definitely not one that duplicates watchdog core
> >> functionality.
> >>
> >>> +{
> >>> +	int new_margin, options;
> >>> +
> >>> +	switch (cmd) {
> >>> +	case WDIOC_GETSUPPORT:
> >>> +		return copy_to_user((struct watchdog_info __user *)arg,
> >>> +		&ds1374_wdt_info, sizeof(ds1374_wdt_info)) ? -EFAULT : 0;
> >>> +
> >>> +	case WDIOC_GETSTATUS:
> >>> +	case WDIOC_GETBOOTSTATUS:
> >>> +		return put_user(0, (int __user *)arg);
> >>> +	case WDIOC_KEEPALIVE:
> >>> +		ds1374_wdt_ping(wdt);
> >>> +		return 0;
> >>> +	case WDIOC_SETTIMEOUT:
> >>> +		if (get_user(new_margin, (int __user *)arg))
> >>> +			return -EFAULT;
> >>> +
> >>> +		/* the hardware's tick rate is 4096 Hz, so
> >>> +		 * the counter value needs to be scaled accordingly
> >>> +		 */
> >>> +		new_margin <<= 12;
> >>> +		if (new_margin < 1 || new_margin > 16777216)
> >>> +			return -EINVAL;
> >>> +
> >>> +		wdt_margin = new_margin;
> >>> +		ds1374_wdt_settimeout(wdt, new_margin);
> >>
> >> Is the idea here to bypass the watchdog subsystem's notion of keeping the
> >> timeout in seconds ? If so, that would be wrong and unacceptable.
> >>
> > It seems take care about 4096Hz for original design in rtc-ds1374.c. I think
> we
> > can just use ioctl() which watchdog core provides and input margin time
> > appropriately.
> >
> >
> >>> +		ds1374_wdt_ping(wdt);
> >>> +		fallthrough;
> >>> +	case WDIOC_GETTIMEOUT:
> >>> +		/* when returning ... inverse is true */
> >>> +		return put_user((wdt_margin >> 12), (int __user *)arg);
> >>> +	case WDIOC_SETOPTIONS:
> >>> +		if (copy_from_user(&options, (int __user *)arg, sizeof(int)))
> >>> +			return -EFAULT;
> >>> +
> >>> +		if (options & WDIOS_DISABLECARD) {
> >>> +			pr_info("disable watchdog\n");
> >>> +			ds1374_wdt_stop(wdt);
> >>> +			return 0;
> >>> +		}
> >>> +
> >>> +		if (options & WDIOS_ENABLECARD) {
> >>> +			pr_info("enable watchdog\n");
> >>> +			ds1374_wdt_settimeout(wdt, wdt_margin);
> >>> +			ds1374_wdt_ping(wdt);
> >>> +			return 0;
> >>> +		}
> >>> +		return -EINVAL;
> >>> +	}
> >>> +	return -ENOTTY;
> >>> +}
> >>> +
> >>> +static int ds1374_wdt_notify_sys(struct notifier_block *this,
> >>> +			unsigned long code, void *unused)
> >>> +{
> >>> +	if (code == SYS_DOWN || code == SYS_HALT)
> >>> +		/* Disable Watchdog */
> >>> +		ds1374_wdt_stop(&ds1374_wdd);
> >>> +	return NOTIFY_DONE;
> >>> +}
> >>> +
> >> Not needed - see below.
> >>
> >>> +static struct notifier_block ds1374_wdt_notifier = {
> >>> +	.notifier_call = ds1374_wdt_notify_sys, };
> >>> +
> >>> +static int ds1374_wdt_probe(struct platform_device *pdev) {
> >>> +	struct ds1374_wdt *drv_data;
> >>> +	struct i2c_client *client = to_i2c_client(pdev->dev.parent);
> >>> +	int ret;
> >>> +
> >>> +	drv_data = devm_kzalloc(&pdev->dev, sizeof(struct ds1374_wdt),
> >>> +				GFP_KERNEL);
> >>> +	if (!drv_data)
> >>> +		return -ENOMEM;
> >>> +
> >>> +	drv_data->wdt = &ds1374_wdd;
> >>> +	drv_data->client = client;
> >>> +	mutex_init(&drv_data->mutex);
> >>> +
> >>> +	watchdog_init_timeout(drv_data->wdt, wdt_margin, &pdev->dev);
> >>> +	watchdog_set_nowayout(drv_data->wdt, nowayout);
> >>> +
> >>> +	watchdog_set_drvdata(drv_data->wdt, drv_data);
> >>> +	platform_set_drvdata(pdev, drv_data);
> >>> +
> >>> +	ret = watchdog_register_device(drv_data->wdt);
> >>
> >> Use devm_watchdog_register_device()
> >>
> >>> +	if (ret) {
> >>> +		dev_err(&pdev->dev, "failed to register Watchdog device\n");
> >>> +		return ret;
> >>> +	}
> >>> +
> >>> +	ret = register_reboot_notifier(&ds1374_wdt_notifier);
> >>
> >> Call watchdog_stop_on_reboot() before calling watchdog_register_device()
> >> instead.
> >>
> >>> +	if (ret) {
> >>> +		watchdog_unregister_device(drv_data->wdt);
> >>> +		return ret;
> >>> +	}
> >>> +
> >>> +	ds1374_wdt_settimeout(drv_data->wdt, wdt_margin);
> >>
> >> Unnecessary here; called from start function.
> >>
> >>> +	dev_info(&pdev->dev, "Dallas/Maxim DS1374 watchdog device
> >>> +enabled\n");
> >>> +
> >>> +	return 0;
> >>> +}
> >>> +
> >>> +static int ds1374_wdt_remove(struct platform_device *pdev) {
> >>> +	struct ds1374_wdt *drv_data = platform_get_drvdata(pdev);
> >>> +
> >>> +	dev_warn(&pdev->dev, "Unregister DS1374 watchdog device\n");
> >>> +	watchdog_unregister_device(drv_data->wdt);
> >>> +	unregister_reboot_notifier(&ds1374_wdt_notifier);
> >>> +
> >>
> >> Call watchdog_stop_on_unregister() before calling
> >> watchdog_register_device().
> >>
> >>> +	return 0;
> >>> +}
> >>> +
> >>> +static void ds1374_wdt_shutdown(struct platform_device *pdev) {
> >>> +	struct ds1374_wdt *drv_data = platform_get_drvdata(pdev);
> >>> +
> >>> +	mutex_lock(&drv_data->mutex);
> >>> +	ds1374_wdt_stop(drv_data->wdt);
> >>> +	mutex_unlock(&drv_data->mutex);
> >>
> >> Unnecessary and pointless.
> >>
> >>> +}
> >>> +
> >>> +static const struct watchdog_ops ds1374_wdt_fops = {
> >>> +	.owner          = THIS_MODULE,
> >>> +	.start          = ds1374_wdt_start,
> >>> +	.stop           = ds1374_wdt_stop,
> >>> +	.ping           = ds1374_wdt_ping,
> >>> +	.set_timeout    = ds1374_wdt_settimeout,
> >>> +	.ioctl          = ds1374_wdt_ioctl,
> >>> +};
> >>> +
> >>> +static struct watchdog_device ds1374_wdd = {
> >>> +	.info           = &ds1374_wdt_info,
> >>> +	.ops            = &ds1374_wdt_fops,
> >>> +	.min_timeout    = TIMER_MARGIN_MIN,
> >>> +	.max_timeout    = TIMER_MARGIN_MAX,
> >>
> >> .timeout should be set here.
> >>
> >> Also, there can (at least in theory) be more than one ds1374 in the system.
> The
> >> code does not support this case. ds1374_wdd should be moved into struct
> >> ds1374_wdt.
> >>
> > Thanks for good suggestion.
> >>> +};
> >>> +
> >>> +static struct platform_driver ds1374_wdt = {
> >>> +	.driver         = {
> >>> +		.owner  = THIS_MODULE,
> >>> +		.name   = DEVNAME,
> >>> +	},
> >>> +	.probe          = ds1374_wdt_probe,
> >>> +	.remove         = ds1374_wdt_remove,
> >>> +	.shutdown       = ds1374_wdt_shutdown,
> >>> +};
> >>> +
> >>> +module_platform_driver(ds1374_wdt);
> >>> +
> >>> +MODULE_AUTHOR("Johnson Chen <johnsonch.chen@moxa.com>");
> >>> +MODULE_DESCRIPTION("Dallas/Maxim DS1374 Watchdog Driver");
> >>> +MODULE_LICENSE("GPL"); MODULE_ALIAS("Platform:ds1374_wdt");
> >>>
> >
> > Best regards,
> > Johnson
> >