[v2,1/1] hwmon: (nct7904) Add watchdog function

[v2,1/1] hwmon: (nct7904) Add watchdog function

[yuechao.zhao]

From: Yuechao Zhao <yuechao.zhao@advantech.com.cn>

implement watchdong functionality into the "hwmon/nct7904.c"

Signed-off-by: Yuechao Zhao <yuechao.zhao@advantech.com.cn>
---
v2:
- Modify dependency of NC7904 into "drivers/hwmon/Kconfig".
---
 drivers/hwmon/Kconfig   |   6 +-
 drivers/hwmon/nct7904.c | 157 +++++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 160 insertions(+), 3 deletions(-)

diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 05a3083..cd0ae82 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -1340,10 +1340,12 @@ config SENSORS_NCT7802
 
 config SENSORS_NCT7904
 	tristate "Nuvoton NCT7904"
-	depends on I2C
+	depends on I2C && WATCHDOG
+	select WATCHDOG_CORE
 	help
 	  If you say yes here you get support for the Nuvoton NCT7904
-	  hardware monitoring chip, including manual fan speed control.
+	  hardware monitoring chip, including manual fan speed control
+	  and support for the integrated watchdog.
 
 	  This driver can also be built as a module. If so, the module
 	  will be called nct7904.
diff --git a/drivers/hwmon/nct7904.c b/drivers/hwmon/nct7904.c
index 1f5743d..137199c 100644
--- a/drivers/hwmon/nct7904.c
+++ b/drivers/hwmon/nct7904.c
@@ -8,6 +8,9 @@
  * Copyright (c) 2019 Advantech
  * Author: Amy.Shih <amy.shih@advantech.com.tw>
  *
+ * Copyright (c) 2020 Advantech
+ * Author: Yuechao Zhao <yuechao.zhao@advantech.com.cn>
+ *
  * Supports the following chips:
  *
  * Chip        #vin  #fan  #pwm  #temp  #dts  chip ID
@@ -20,6 +23,7 @@
 #include <linux/i2c.h>
 #include <linux/mutex.h>
 #include <linux/hwmon.h>
+#include <linux/watchdog.h>
 
 #define VENDOR_ID_REG		0x7A	/* Any bank */
 #define NUVOTON_ID		0x50
@@ -87,18 +91,39 @@
 #define FANCTL1_FMR_REG		0x00	/* Bank 3; 1 reg per channel */
 #define FANCTL1_OUT_REG		0x10	/* Bank 3; 1 reg per channel */
 
+#define WDT_LOCK_REG		0xE0	/* W/O Lock Watchdog Register */
+#define WDT_EN_REG		0xE1	/* R/O Watchdog Enable Register */
+#define WDT_STS_REG		0xE2	/* R/O Watchdog Status Register */
+#define WDT_TIMER_REG		0xE3	/* R/W Watchdog Timer Register */
+#define WDT_SOFT_EN		0x55	/* Enable soft watchdog timer */
+#define WDT_SOFT_DIS		0xAA	/* Disable soft watchdog timer */
+
 #define VOLT_MONITOR_MODE	0x0
 #define THERMAL_DIODE_MODE	0x1
 #define THERMISTOR_MODE		0x3
 
 #define ENABLE_TSI	BIT(1)
 
+#define WATCHDOG_TIMEOUT	1	/* 1 minute default timeout */
+static int ping_timeout = WATCHDOG_TIMEOUT; /* default feeding timeout */
+
+static int timeout = WATCHDOG_TIMEOUT;
+module_param(timeout, int, 0);
+MODULE_PARM_DESC(timeout, "Watchdog timeout in minutes. 1 <= timeout <= 255, default="
+			__MODULE_STRING(WATCHODOG_TIMEOUT) ".");
+
+static bool nowayout = WATCHDOG_NOWAYOUT;
+module_param(nowayout, bool, 0);
+MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started once started (default="
+			__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
+
 static const unsigned short normal_i2c[] = {
 	0x2d, 0x2e, I2C_CLIENT_END
 };
 
 struct nct7904_data {
 	struct i2c_client *client;
+	struct watchdog_device wdt;
 	struct mutex bank_lock;
 	int bank_sel;
 	u32 fanin_mask;
@@ -889,6 +914,91 @@ static int nct7904_detect(struct i2c_client *client,
 	.info = nct7904_info,
 };
 
+/*
+ * Wathcdog Function
+ */
+static int nct7904_wdt_start(struct watchdog_device *wdt)
+{
+	int ret;
+	struct nct7904_data *data = watchdog_get_drvdata(wdt);
+
+	/* Disable soft watchdog timer first */
+	ret = nct7904_write_reg(data, BANK_0, WDT_LOCK_REG, WDT_SOFT_DIS);
+	if (ret < 0)
+		return ret;
+
+	/* Enable soft watchdog timer */
+	ret = nct7904_write_reg(data, BANK_0, WDT_LOCK_REG, WDT_SOFT_EN);
+	return ret;
+}
+
+static int nct7904_wdt_stop(struct watchdog_device *wdt)
+{
+	struct nct7904_data *data = watchdog_get_drvdata(wdt);
+	int ret;
+
+	ret = nct7904_write_reg(data, BANK_0, WDT_LOCK_REG, WDT_SOFT_DIS);
+
+	return ret;
+}
+
+static int nct7904_wdt_set_timeout(struct watchdog_device *wdt,
+				   unsigned int timeout)
+{
+	struct nct7904_data *data = watchdog_get_drvdata(wdt);
+
+	ping_timeout = timeout / 60;
+
+	return nct7904_write_reg(data, BANK_0, WDT_TIMER_REG, ping_timeout);
+}
+
+static int nct7904_wdt_ping(struct watchdog_device *wdt)
+{
+	/*
+	 * Note:
+	 * NCT7904 is not supported refresh WDT_TIMER_REG register when the
+	 * watchdog is actiove. Please disable watchdog before fedding the
+	 * watchdog and enable it again.
+	 */
+	struct nct7904_data *data = watchdog_get_drvdata(wdt);
+	int ret;
+
+	/* Disable soft watchdog timer */
+	ret = nct7904_write_reg(data, BANK_0, WDT_LOCK_REG, WDT_SOFT_DIS);
+	if (ret < 0)
+		goto ping_err;
+
+	/* feed watchdog */
+	ret = nct7904_write_reg(data, BANK_0, WDT_TIMER_REG, ping_timeout);
+	if (ret < 0)
+		goto ping_err;
+
+	/* Enable soft watchdog timer */
+	ret = nct7904_write_reg(data, BANK_0, WDT_TIMER_REG, WDT_SOFT_EN);
+	if (ret < 0)
+		goto ping_err;
+
+	return 0;
+
+ping_err:
+	pr_err("nct7904 ping error\n");
+	return ret;
+}
+
+static const struct watchdog_info nct7904_wdt_info = {
+	.options	= WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING |
+				WDIOF_MAGICCLOSE,
+	.identity	= "nct7904 watchdog",
+};
+
+static const struct watchdog_ops nct7904_wdt_ops = {
+	.owner		= THIS_MODULE,
+	.start		= nct7904_wdt_start,
+	.stop		= nct7904_wdt_stop,
+	.ping		= nct7904_wdt_ping,
+	.set_timeout	= nct7904_wdt_set_timeout,
+};
+
 static int nct7904_probe(struct i2c_client *client,
 			 const struct i2c_device_id *id)
 {
@@ -1012,7 +1122,51 @@ static int nct7904_probe(struct i2c_client *client,
 	hwmon_dev =
 		devm_hwmon_device_register_with_info(dev, client->name, data,
 						     &nct7904_chip_info, NULL);
-	return PTR_ERR_OR_ZERO(hwmon_dev);
+	ret = PTR_ERR_OR_ZERO(hwmon_dev);
+	if (ret)
+		return ret;
+
+	/* Watchdog initialization */
+	data->wdt.ops = &nct7904_wdt_ops;
+	data->wdt.info = &nct7904_wdt_info;
+
+	data->wdt.timeout = timeout * 60; /* in seconds */
+	data->wdt.min_timeout = 1;
+	data->wdt.max_timeout = 15300;
+	data->wdt.parent = &client->dev;
+
+	watchdog_init_timeout(&data->wdt, timeout, &client->dev);
+	watchdog_set_nowayout(&data->wdt, nowayout);
+	watchdog_set_drvdata(&data->wdt, data);
+
+	i2c_set_clientdata(client, data);
+
+	ret = watchdog_register_device(&data->wdt);
+	if (ret)
+		return ret;
+
+	dev_info(&client->dev, "NCT7904 HWMON and Watchdog device probed\n");
+
+	return ret;
+}
+
+static int nct7904_remove(struct i2c_client *client)
+{
+	/*
+	 * HWMON use devm_hwmon_device_register_with_info() register. So, do
+	 * not need unregister it manually.
+	 */
+	struct nct7904_data *data = i2c_get_clientdata(client);
+
+	/* disable watchdog */
+	if (!nowayout)
+		nct7904_write_reg(data, BANK_0, WDT_LOCK_REG, WDT_SOFT_DIS);
+
+	watchdog_unregister_device(&data->wdt);
+
+	dev_info(&client->dev, "NCT7904 driver removed\n");
+
+	return 0;
 }
 
 static const struct i2c_device_id nct7904_id[] = {
@@ -1030,6 +1184,7 @@ static int nct7904_probe(struct i2c_client *client,
 	.id_table = nct7904_id,
 	.detect = nct7904_detect,
 	.address_list = normal_i2c,
+	.remove = nct7904_remove,
 };
 
 module_i2c_driver(nct7904_driver);
-- 
1.8.3.1

Re: [v2,1/1] hwmon: (nct7904) Add watchdog function

[Guenter Roeck]

On Wed, Mar 25, 2020 at 08:22:37AM +0000, yuechao.zhao@advantech.com.cn wrote:
> From: Yuechao Zhao <yuechao.zhao@advantech.com.cn>
> 
> implement watchdong functionality into the "hwmon/nct7904.c"
> 
> Signed-off-by: Yuechao Zhao <yuechao.zhao@advantech.com.cn>
> ---
> v2:
> - Modify dependency of NC7904 into "drivers/hwmon/Kconfig".
> ---
>  drivers/hwmon/Kconfig   |   6 +-
>  drivers/hwmon/nct7904.c | 157 +++++++++++++++++++++++++++++++++++++++++++++++-
>  2 files changed, 160 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> index 05a3083..cd0ae82 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -1340,10 +1340,12 @@ config SENSORS_NCT7802
>  
>  config SENSORS_NCT7904
>  	tristate "Nuvoton NCT7904"
> -	depends on I2C
> +	depends on I2C && WATCHDOG
> +	select WATCHDOG_CORE
>  	help
>  	  If you say yes here you get support for the Nuvoton NCT7904
> -	  hardware monitoring chip, including manual fan speed control.
> +	  hardware monitoring chip, including manual fan speed control
> +	  and support for the integrated watchdog.
>  
>  	  This driver can also be built as a module. If so, the module
>  	  will be called nct7904.
> diff --git a/drivers/hwmon/nct7904.c b/drivers/hwmon/nct7904.c
> index 1f5743d..137199c 100644
> --- a/drivers/hwmon/nct7904.c
> +++ b/drivers/hwmon/nct7904.c
> @@ -8,6 +8,9 @@
>   * Copyright (c) 2019 Advantech
>   * Author: Amy.Shih <amy.shih@advantech.com.tw>
>   *
> + * Copyright (c) 2020 Advantech
> + * Author: Yuechao Zhao <yuechao.zhao@advantech.com.cn>
> + *
>   * Supports the following chips:
>   *
>   * Chip        #vin  #fan  #pwm  #temp  #dts  chip ID
> @@ -20,6 +23,7 @@
>  #include <linux/i2c.h>
>  #include <linux/mutex.h>
>  #include <linux/hwmon.h>
> +#include <linux/watchdog.h>
>  
>  #define VENDOR_ID_REG		0x7A	/* Any bank */
>  #define NUVOTON_ID		0x50
> @@ -87,18 +91,39 @@
>  #define FANCTL1_FMR_REG		0x00	/* Bank 3; 1 reg per channel */
>  #define FANCTL1_OUT_REG		0x10	/* Bank 3; 1 reg per channel */
>  
> +#define WDT_LOCK_REG		0xE0	/* W/O Lock Watchdog Register */
> +#define WDT_EN_REG		0xE1	/* R/O Watchdog Enable Register */
> +#define WDT_STS_REG		0xE2	/* R/O Watchdog Status Register */
> +#define WDT_TIMER_REG		0xE3	/* R/W Watchdog Timer Register */
> +#define WDT_SOFT_EN		0x55	/* Enable soft watchdog timer */
> +#define WDT_SOFT_DIS		0xAA	/* Disable soft watchdog timer */
> +
>  #define VOLT_MONITOR_MODE	0x0
>  #define THERMAL_DIODE_MODE	0x1
>  #define THERMISTOR_MODE		0x3
>  
>  #define ENABLE_TSI	BIT(1)
>  
> +#define WATCHDOG_TIMEOUT	1	/* 1 minute default timeout */

> +static int ping_timeout = WATCHDOG_TIMEOUT; /* default feeding timeout */

Please no static variables; at least in theory there could be multiple
NCT7904 in the system. Just use wdt->timeout / 60.

> +
> +static int timeout = WATCHDOG_TIMEOUT;
> +module_param(timeout, int, 0);
> +MODULE_PARM_DESC(timeout, "Watchdog timeout in minutes. 1 <= timeout <= 255, default="
> +			__MODULE_STRING(WATCHODOG_TIMEOUT) ".");
> +
> +static bool nowayout = WATCHDOG_NOWAYOUT;
> +module_param(nowayout, bool, 0);
> +MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started once started (default="
> +			__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
> +
>  static const unsigned short normal_i2c[] = {
>  	0x2d, 0x2e, I2C_CLIENT_END
>  };
>  
>  struct nct7904_data {
>  	struct i2c_client *client;
> +	struct watchdog_device wdt;
>  	struct mutex bank_lock;
>  	int bank_sel;
>  	u32 fanin_mask;
> @@ -889,6 +914,91 @@ static int nct7904_detect(struct i2c_client *client,
>  	.info = nct7904_info,
>  };
>  
> +/*
> + * Wathcdog Function
> + */
> +static int nct7904_wdt_start(struct watchdog_device *wdt)
> +{
> +	int ret;
> +	struct nct7904_data *data = watchdog_get_drvdata(wdt);
> +
> +	/* Disable soft watchdog timer first */
> +	ret = nct7904_write_reg(data, BANK_0, WDT_LOCK_REG, WDT_SOFT_DIS);
> +	if (ret < 0)
> +		return ret;
> +
Is that really necessary ?

> +	/* Enable soft watchdog timer */
> +	ret = nct7904_write_reg(data, BANK_0, WDT_LOCK_REG, WDT_SOFT_EN);
> +	return ret;

Just return immediately here, without assigning to ret.

> +}
> +
> +static int nct7904_wdt_stop(struct watchdog_device *wdt)
> +{
> +	struct nct7904_data *data = watchdog_get_drvdata(wdt);
> +	int ret;
> +
> +	ret = nct7904_write_reg(data, BANK_0, WDT_LOCK_REG, WDT_SOFT_DIS);
> +
> +	return ret;

Same here. 'ret' is unnecessary.

> +}
> +
> +static int nct7904_wdt_set_timeout(struct watchdog_device *wdt,
> +				   unsigned int timeout)
> +{
> +	struct nct7904_data *data = watchdog_get_drvdata(wdt);
> +
> +	ping_timeout = timeout / 60;

The code should update wdt->timeout, and then use wdt->timeout as basis for
setting the chip timeout.

> +
> +	return nct7904_write_reg(data, BANK_0, WDT_TIMER_REG, ping_timeout);
> +}
> +
> +static int nct7904_wdt_ping(struct watchdog_device *wdt)
> +{
> +	/*
> +	 * Note:
> +	 * NCT7904 is not supported refresh WDT_TIMER_REG register when the

"does not support refreshing ..." if I understand correctly.

> +	 * watchdog is actiove. Please disable watchdog before fedding the

s/actiove/active/
s/fedding/feeding/

> +	 * watchdog and enable it again.
> +	 */
> +	struct nct7904_data *data = watchdog_get_drvdata(wdt);
> +	int ret;
> +
> +	/* Disable soft watchdog timer */
> +	ret = nct7904_write_reg(data, BANK_0, WDT_LOCK_REG, WDT_SOFT_DIS);
> +	if (ret < 0)
> +		goto ping_err;
> +
> +	/* feed watchdog */
> +	ret = nct7904_write_reg(data, BANK_0, WDT_TIMER_REG, ping_timeout);

This should use wdt->timeout / 60 (see above).

Is it necessary to update the timeout ? The datasheet doesn't describe it well.

If the timer register is updated, you could possibly implement
a get_timeout function.

> +	if (ret < 0)
> +		goto ping_err;
> +
> +	/* Enable soft watchdog timer */
> +	ret = nct7904_write_reg(data, BANK_0, WDT_TIMER_REG, WDT_SOFT_EN);
> +	if (ret < 0)
> +		goto ping_err;
> +
> +	return 0;
> +
> +ping_err:
> +	pr_err("nct7904 ping error\n");

I am a concerned about this; if the error is persistent, it would
clog up the log. Please just return the error.

> +	return ret;
> +}
> +
> +static const struct watchdog_info nct7904_wdt_info = {
> +	.options	= WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING |
> +				WDIOF_MAGICCLOSE,
> +	.identity	= "nct7904 watchdog",
> +};
> +
> +static const struct watchdog_ops nct7904_wdt_ops = {
> +	.owner		= THIS_MODULE,
> +	.start		= nct7904_wdt_start,
> +	.stop		= nct7904_wdt_stop,
> +	.ping		= nct7904_wdt_ping,
> +	.set_timeout	= nct7904_wdt_set_timeout,
> +};
> +
>  static int nct7904_probe(struct i2c_client *client,
>  			 const struct i2c_device_id *id)
>  {
> @@ -1012,7 +1122,51 @@ static int nct7904_probe(struct i2c_client *client,
>  	hwmon_dev =
>  		devm_hwmon_device_register_with_info(dev, client->name, data,
>  						     &nct7904_chip_info, NULL);
> -	return PTR_ERR_OR_ZERO(hwmon_dev);
> +	ret = PTR_ERR_OR_ZERO(hwmon_dev);
> +	if (ret)
> +		return ret;
> +
> +	/* Watchdog initialization */
> +	data->wdt.ops = &nct7904_wdt_ops;
> +	data->wdt.info = &nct7904_wdt_info;
> +
> +	data->wdt.timeout = timeout * 60; /* in seconds */
> +	data->wdt.min_timeout = 1;
> +	data->wdt.max_timeout = 15300;

Please make it 60 * 255 (or use a respective define) to clarify
where the number comes from.

> +	data->wdt.parent = &client->dev;
> +
> +	watchdog_init_timeout(&data->wdt, timeout, &client->dev);
> +	watchdog_set_nowayout(&data->wdt, nowayout);
> +	watchdog_set_drvdata(&data->wdt, data);
> +
> +	i2c_set_clientdata(client, data);
> +
> +	ret = watchdog_register_device(&data->wdt);
> +	if (ret)
> +		return ret;

Please use devm_watchdog_register_device()

> +
> +	dev_info(&client->dev, "NCT7904 HWMON and Watchdog device probed\n");
> +
I am not in favor of such noise.

> +	return ret;
> +}
> +
> +static int nct7904_remove(struct i2c_client *client)
> +{
> +	/*
> +	 * HWMON use devm_hwmon_device_register_with_info() register. So, do
> +	 * not need unregister it manually.
> +	 */
> +	struct nct7904_data *data = i2c_get_clientdata(client);
> +
> +	/* disable watchdog */
> +	if (!nowayout)
> +		nct7904_write_reg(data, BANK_0, WDT_LOCK_REG, WDT_SOFT_DIS);

Please use watchdog_stop_on_unregister().

> +
> +	watchdog_unregister_device(&data->wdt);
> +
> +	dev_info(&client->dev, "NCT7904 driver removed\n");
> +

Please no such noise.

> +	return 0;
>  }
>  
>  static const struct i2c_device_id nct7904_id[] = {
> @@ -1030,6 +1184,7 @@ static int nct7904_probe(struct i2c_client *client,
>  	.id_table = nct7904_id,
>  	.detect = nct7904_detect,
>  	.address_list = normal_i2c,
> +	.remove = nct7904_remove,
>  };
>  
>  module_i2c_driver(nct7904_driver);
> -- 
> 1.8.3.1
> 

Re: 答复: [v2,1/1] hwmon: (nct7904) Add watchdog function

[Guenter Roeck]

On 3/26/20 7:39 PM, yuechao.zhao(赵越超) wrote:
> Hi Guenter
> Thank you very much for the suggestion
> 
> But, I wish to consult you on a few questions.
> The NCT7904 is very special in watchdog function. Its minimum unit is minutes.
> So, what unit do we use for setting the timeout in user space. Minutes or seconds?
> Does the kernel document specify it?
> 
Documentation/watchdog/watchdog-api.rst very clearly specifies that
the timeout is set in seconds.

> Also, about this suggestion:
> 	> +	data->wdt.timeout = timeout * 60; /* in seconds */
> 	> +	data->wdt.min_timeout = 1;
> 	> +	data->wdt.max_timeout = 15300;
> 	Please make it 60 * 255 (or use a respective define) to clarify where the number comes from.
> 
> The reason for not use 60 * 255(or use a respective define ) is that we will set the default timeout with 
> "timeout" parameter when "insmod nct7904.ko".

This is not an argument for
	data->wdt.max_timeout = 15300;
instead of
	data->wdt.max_timeout = 60 * 255;
or

#define MAX_TIMEOUT	(60 * 255)
...
	data->wdt.max_timeout = MAX_TIMEOUT;

> The relevant code as follows:
> 	> +static int timeout = WATCHDOG_TIMEOUT; module_param(timeout, int, 0); 
> 	> +MODULE_PARM_DESC(timeout, "Watchdog timeout in minutes. 1 <= timeout <= 255, default="
> 	> +			__MODULE_STRING(WATCHODOG_TIMEOUT) ".");
> 

I accepted that you want to have a module parameter which specifies
the timeout in minutes instead of seconds (as would be customary).
However, I completely fail to understand what that has to do with
using an unexplained constant of "15300" when setting the maximum
timeout variable instead of "60 * 255" or, as I had suggested, a
define.

Thanks,
Guenter

Re: 答复: 答复: [v2,1/1] hwmon: (nct7904) Add watchdog function

[Guenter Roeck]

On 3/29/20 10:42 PM, yuechao.zhao(赵越超) wrote:
> Hi Guenter
> 
> Thank you very much.
> I misunderstood your suggestion. (Please make it 60 * 255 (or use a respective define) to clarify where the number comes from)
> So, I will modify it.
> Also, I will define a module parameter which specifies the timeout in minutes instead of seconds.
> 
The module parameter already specifies the timeout in minutes.

Guenter

> Thanks
> Yuechao
> 
> -----邮件原件-----
> 发件人: Guenter Roeck [mailto:groeck7@gmail.com] 代表 Guenter Roeck
> 发送时间: 2020年3月28日 4:54
> 收件人: yuechao.zhao(赵越超)
> 抄送: 345351830@qq.com; Jean Delvare; linux-hwmon@vger.kernel.org; linux-kernel@vger.kernel.org; Amy.Shih; Oakley.Ding; Jia.Sui(贾睢); shengkui.leng(冷胜魁); Rainbow.Zhang(張玉)
> 主题: Re: 答复: [v2,1/1] hwmon: (nct7904) Add watchdog function
> 
> On 3/26/20 7:39 PM, yuechao.zhao(赵越超) wrote:
>> Hi Guenter
>> Thank you very much for the suggestion
>>
>> But, I wish to consult you on a few questions.
>> The NCT7904 is very special in watchdog function. Its minimum unit is minutes.
>> So, what unit do we use for setting the timeout in user space. Minutes or seconds?
>> Does the kernel document specify it?
>>
> Documentation/watchdog/watchdog-api.rst very clearly specifies that the timeout is set in seconds.
> 
>> Also, about this suggestion:
>> 	> +	data->wdt.timeout = timeout * 60; /* in seconds */
>> 	> +	data->wdt.min_timeout = 1;
>> 	> +	data->wdt.max_timeout = 15300;
>> 	Please make it 60 * 255 (or use a respective define) to clarify where the number comes from.
>>
>> The reason for not use 60 * 255(or use a respective define ) is that 
>> we will set the default timeout with "timeout" parameter when "insmod nct7904.ko".
> 
> This is not an argument for
> 	data->wdt.max_timeout = 15300;
> instead of
> 	data->wdt.max_timeout = 60 * 255;
> or
> 
> #define MAX_TIMEOUT	(60 * 255)
> ...
> 	data->wdt.max_timeout = MAX_TIMEOUT;
> 
>> The relevant code as follows:
>> 	> +static int timeout = WATCHDOG_TIMEOUT; module_param(timeout, int, 0); 
>> 	> +MODULE_PARM_DESC(timeout, "Watchdog timeout in minutes. 1 <= timeout <= 255, default="
>> 	> +			__MODULE_STRING(WATCHODOG_TIMEOUT) ".");
>>
> 
> I accepted that you want to have a module parameter which specifies the timeout in minutes instead of seconds (as would be customary).
> However, I completely fail to understand what that has to do with using an unexplained constant of "15300" when setting the maximum timeout variable instead of "60 * 255" or, as I had suggested, a define.
> 
> Thanks,
> Guenter
>