[PATCH v3 0/2] watchdog: w83627hf_wdt: Add NCT6126 support and improve handling of running watchdog

[PATCH v3 0/2] watchdog: w83627hf_wdt: Add NCT6126 support and improve handling of running watchdog

[Paul Louvel]

This series brings two small improvements to the w83627hf_wdt driver.

The first patch adds support for the Nuvoton NCT6126 Super I/O chip. The
NCT6126 is compatible with the existing driver but requires reading the
full 16-bit chip ID, as it shares its high-byte ID with the NCT6116.

The second patch improves the handling of watchdogs that are already
running when the driver probes. Instead of issuing a single keepalive
using the default timeout, it relies on the watchdog core's
WDOG_HW_RUNNING support to automatically maintain the watchdog until
userspace opens the device.

Signed-off-by: Paul Louvel <paul.louvel@bootlin.com>
---
Changes in v3:
- Forgot to add case in w83627hf_init() with the chip. Not detected
  during testing because the BIOS probably configure it anyway on boot.
- Link to v2: https://patch.msgid.link/20260706-w83627hf_wdt-nct6126d-v2-0-77af74af88ae@bootlin.com

Changes in v2:
- Small mistake in the first patch. The NCT6116_ID macro is redefined.
  Fix it.

To: Wim Van Sebroeck <wim@linux-watchdog.org>
To: Guenter Roeck <linux@roeck-us.net>
Cc: linux-watchdog@vger.kernel.org
Cc: linux-kernel@vger.kernel.org

---
Paul Louvel (2):
      watchdog: w83627hf_wdt: Add support for Nuvoton NCT6126
      watchdog: w83627hf_wdt: Use WDOG_HW_RUNNING for running chip on boot

 drivers/watchdog/w83627hf_wdt.c | 20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)
---
base-commit: 028ef9c96e96197026887c0f092424679298aae8
change-id: 20260705-w83627hf_wdt-nct6126d-9a016bf7c936

Best regards,
--  
Paul Louvel, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

[PATCH v3 1/2] watchdog: w83627hf_wdt: Add support for Nuvoton NCT6126

[Paul Louvel]

Add support for the hardware watchdog integrated in the Nuvoton NCT6126
Super I/O chip. This device is used on a number of x86 single-board
computers and is compatible with the w83627hf_wdt driver.

Unlike most supported chips, the NCT6126 shares the same high-byte chip
ID as the NCT6116. Read the low byte of the chip ID as well to
distinguish between the two devices and identify the NCT6126 correctly.

Signed-off-by: Paul Louvel <paul.louvel@bootlin.com>
---
 drivers/watchdog/w83627hf_wdt.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/drivers/watchdog/w83627hf_wdt.c b/drivers/watchdog/w83627hf_wdt.c
index bc33b63c5a5d..a6dfa9d01702 100644
--- a/drivers/watchdog/w83627hf_wdt.c
+++ b/drivers/watchdog/w83627hf_wdt.c
@@ -49,7 +49,7 @@ static int wdt_cfg_leave = 0xAA;/* key to lock configuration space */
 enum chips { w83627hf, w83627s, w83697hf, w83697ug, w83637hf, w83627thf,
 	     w83687thf, w83627ehf, w83627dhg, w83627uhg, w83667hg, w83627dhg_p,
 	     w83667hg_b, nct6775, nct6776, nct6779, nct6791, nct6792, nct6793,
-	     nct6795, nct6796, nct6102, nct6116 };
+	     nct6795, nct6796, nct6102, nct6116, nct6126 };
 
 static int timeout;			/* in seconds */
 module_param(timeout, int, 0);
@@ -94,7 +94,9 @@ MODULE_PARM_DESC(early_disable, "Disable watchdog at boot time (default=0)");
 #define NCT6775_ID		0xb4
 #define NCT6776_ID		0xc3
 #define NCT6102_ID		0xc4
-#define NCT6116_ID		0xd2
+#define NCT6116_ID		0xd2	/* also NCT6126D */
+#define NCT6126_VER_A_LOW_ID	0x83	/* ... version A */
+#define NCT6126_VER_B_LOW_ID	0x84	/* ... version B */
 #define NCT6779_ID		0xc5
 #define NCT6791_ID		0xc8
 #define NCT6792_ID		0xc9
@@ -217,6 +219,7 @@ static int w83627hf_init(struct watchdog_device *wdog, enum chips chip)
 	case nct6796:
 	case nct6102:
 	case nct6116:
+	case nct6126:
 		/*
 		 * These chips have a fixed WDTO# output pin (W83627UHG),
 		 * or support more than one WDTO# output pin.
@@ -428,7 +431,12 @@ static int wdt_find(int addr)
 		cr_wdt_csr = NCT6102D_WDT_CSR;
 		break;
 	case NCT6116_ID:
-		ret = nct6116;
+		val = superio_inb(0x21);
+		if (val == NCT6126_VER_A_LOW_ID || val == NCT6126_VER_B_LOW_ID)
+			ret = nct6126;
+		else
+			ret = nct6116;
+
 		cr_wdt_timeout = NCT6102D_WDT_TIMEOUT;
 		cr_wdt_control = NCT6102D_WDT_CONTROL;
 		cr_wdt_csr = NCT6102D_WDT_CSR;
@@ -499,6 +507,7 @@ static int __init wdt_init(void)
 		"NCT6796",
 		"NCT6102",
 		"NCT6116",
+		"NCT6126"
 	};
 
 	/* Apply system-specific quirks */

-- 
2.55.0

[PATCH v3 2/2] watchdog: w83627hf_wdt: Use WDOG_HW_RUNNING for running chip on boot

[Paul Louvel]

If the watchdog is already running when the driver is initialized, the
driver currently refreshes it once using the default timeout of 60
seconds.

Since commit ee142889e32f ("watchdog: Introduce WDOG_HW_RUNNING flag"),
the watchdog core can keep an already running watchdog alive even when
the watchdog device is not open. This is more robust than issuing a
single manual keepalive during initialization.

Replace the manual watchdog refresh with the WDOG_HW_RUNNING flag and
let the watchdog core handle periodic keepalives until user space takes
over.

Signed-off-by: Paul Louvel <paul.louvel@bootlin.com>
---
 drivers/watchdog/w83627hf_wdt.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/watchdog/w83627hf_wdt.c b/drivers/watchdog/w83627hf_wdt.c
index a6dfa9d01702..27ef1cce3a14 100644
--- a/drivers/watchdog/w83627hf_wdt.c
+++ b/drivers/watchdog/w83627hf_wdt.c
@@ -241,9 +241,8 @@ static int w83627hf_init(struct watchdog_device *wdog, enum chips chip)
 			pr_warn("Stopping previously enabled watchdog until userland kicks in\n");
 			superio_outb(cr_wdt_timeout, 0);
 		} else {
-			pr_info("Watchdog already running. Resetting timeout to %d sec\n",
-				wdog->timeout);
-			superio_outb(cr_wdt_timeout, wdog->timeout);
+			pr_info("Watchdog already running.\n");
+			set_bit(WDOG_HW_RUNNING, &wdog->status);
 		}
 	}
 

-- 
2.55.0

Re: [PATCH v3 1/2] watchdog: w83627hf_wdt: Add support for Nuvoton NCT6126

[Guenter Roeck]

On 7/6/26 03:29, Paul Louvel wrote:
> Add support for the hardware watchdog integrated in the Nuvoton NCT6126
> Super I/O chip. This device is used on a number of x86 single-board
> computers and is compatible with the w83627hf_wdt driver.
> 
> Unlike most supported chips, the NCT6126 shares the same high-byte chip
> ID as the NCT6116. Read the low byte of the chip ID as well to
> distinguish between the two devices and identify the NCT6126 correctly.
> 

Doesn't that (and the code below) mean that the driver already supports
the chip, only it identifies it as NCT6116 instead of NCT6126 ?

This means that the commit message is misleading: It should say that
the chip is already supported but misidentified, and that the added
code helps to correctly identify the chip.

Guenter

> Signed-off-by: Paul Louvel <paul.louvel@bootlin.com>
> ---
>   drivers/watchdog/w83627hf_wdt.c | 15 ++++++++++++---
>   1 file changed, 12 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/watchdog/w83627hf_wdt.c b/drivers/watchdog/w83627hf_wdt.c
> index bc33b63c5a5d..a6dfa9d01702 100644
> --- a/drivers/watchdog/w83627hf_wdt.c
> +++ b/drivers/watchdog/w83627hf_wdt.c
> @@ -49,7 +49,7 @@ static int wdt_cfg_leave = 0xAA;/* key to lock configuration space */
>   enum chips { w83627hf, w83627s, w83697hf, w83697ug, w83637hf, w83627thf,
>   	     w83687thf, w83627ehf, w83627dhg, w83627uhg, w83667hg, w83627dhg_p,
>   	     w83667hg_b, nct6775, nct6776, nct6779, nct6791, nct6792, nct6793,
> -	     nct6795, nct6796, nct6102, nct6116 };
> +	     nct6795, nct6796, nct6102, nct6116, nct6126 };
>   
>   static int timeout;			/* in seconds */
>   module_param(timeout, int, 0);
> @@ -94,7 +94,9 @@ MODULE_PARM_DESC(early_disable, "Disable watchdog at boot time (default=0)");
>   #define NCT6775_ID		0xb4
>   #define NCT6776_ID		0xc3
>   #define NCT6102_ID		0xc4
> -#define NCT6116_ID		0xd2
> +#define NCT6116_ID		0xd2	/* also NCT6126D */
> +#define NCT6126_VER_A_LOW_ID	0x83	/* ... version A */
> +#define NCT6126_VER_B_LOW_ID	0x84	/* ... version B */
>   #define NCT6779_ID		0xc5
>   #define NCT6791_ID		0xc8
>   #define NCT6792_ID		0xc9
> @@ -217,6 +219,7 @@ static int w83627hf_init(struct watchdog_device *wdog, enum chips chip)
>   	case nct6796:
>   	case nct6102:
>   	case nct6116:
> +	case nct6126:
>   		/*
>   		 * These chips have a fixed WDTO# output pin (W83627UHG),
>   		 * or support more than one WDTO# output pin.
> @@ -428,7 +431,12 @@ static int wdt_find(int addr)
>   		cr_wdt_csr = NCT6102D_WDT_CSR;
>   		break;
>   	case NCT6116_ID:
> -		ret = nct6116;
> +		val = superio_inb(0x21);
> +		if (val == NCT6126_VER_A_LOW_ID || val == NCT6126_VER_B_LOW_ID)
> +			ret = nct6126;
> +		else
> +			ret = nct6116;
> +
>   		cr_wdt_timeout = NCT6102D_WDT_TIMEOUT;
>   		cr_wdt_control = NCT6102D_WDT_CONTROL;
>   		cr_wdt_csr = NCT6102D_WDT_CSR;
> @@ -499,6 +507,7 @@ static int __init wdt_init(void)
>   		"NCT6796",
>   		"NCT6102",
>   		"NCT6116",
> +		"NCT6126"
>   	};
>   
>   	/* Apply system-specific quirks */
> 

Re: [PATCH v3 1/2] watchdog: w83627hf_wdt: Add support for Nuvoton NCT6126

[Paul Louvel]

On Mon Jul 6, 2026 at 4:14 PM CEST, Guenter Roeck wrote:
> On 7/6/26 03:29, Paul Louvel wrote:
>> Add support for the hardware watchdog integrated in the Nuvoton NCT6126
>> Super I/O chip. This device is used on a number of x86 single-board
>> computers and is compatible with the w83627hf_wdt driver.
>> 
>> Unlike most supported chips, the NCT6126 shares the same high-byte chip
>> ID as the NCT6116. Read the low byte of the chip ID as well to
>> distinguish between the two devices and identify the NCT6126 correctly.
>> 
>
> Doesn't that (and the code below) mean that the driver already supports
> the chip, only it identifies it as NCT6116 instead of NCT6126 ?

Yes, because they have the same high-byte chip ID.

>
> This means that the commit message is misleading: It should say that
> the chip is already supported but misidentified, and that the added
> code helps to correctly identify the chip.

Indeed. My bad !

>
> Guenter
>
>> Signed-off-by: Paul Louvel <paul.louvel@bootlin.com>
>> ---
>>   drivers/watchdog/w83627hf_wdt.c | 15 ++++++++++++---
>>   1 file changed, 12 insertions(+), 3 deletions(-)
>> 
>> diff --git a/drivers/watchdog/w83627hf_wdt.c b/drivers/watchdog/w83627hf_wdt.c
>> index bc33b63c5a5d..a6dfa9d01702 100644
>> --- a/drivers/watchdog/w83627hf_wdt.c
>> +++ b/drivers/watchdog/w83627hf_wdt.c
>> @@ -49,7 +49,7 @@ static int wdt_cfg_leave = 0xAA;/* key to lock configuration space */
>>   enum chips { w83627hf, w83627s, w83697hf, w83697ug, w83637hf, w83627thf,
>>   	     w83687thf, w83627ehf, w83627dhg, w83627uhg, w83667hg, w83627dhg_p,
>>   	     w83667hg_b, nct6775, nct6776, nct6779, nct6791, nct6792, nct6793,
>> -	     nct6795, nct6796, nct6102, nct6116 };
>> +	     nct6795, nct6796, nct6102, nct6116, nct6126 };
>>   
>>   static int timeout;			/* in seconds */
>>   module_param(timeout, int, 0);
>> @@ -94,7 +94,9 @@ MODULE_PARM_DESC(early_disable, "Disable watchdog at boot time (default=0)");
>>   #define NCT6775_ID		0xb4
>>   #define NCT6776_ID		0xc3
>>   #define NCT6102_ID		0xc4
>> -#define NCT6116_ID		0xd2
>> +#define NCT6116_ID		0xd2	/* also NCT6126D */
>> +#define NCT6126_VER_A_LOW_ID	0x83	/* ... version A */
>> +#define NCT6126_VER_B_LOW_ID	0x84	/* ... version B */
>>   #define NCT6779_ID		0xc5
>>   #define NCT6791_ID		0xc8
>>   #define NCT6792_ID		0xc9
>> @@ -217,6 +219,7 @@ static int w83627hf_init(struct watchdog_device *wdog, enum chips chip)
>>   	case nct6796:
>>   	case nct6102:
>>   	case nct6116:
>> +	case nct6126:
>>   		/*
>>   		 * These chips have a fixed WDTO# output pin (W83627UHG),
>>   		 * or support more than one WDTO# output pin.
>> @@ -428,7 +431,12 @@ static int wdt_find(int addr)
>>   		cr_wdt_csr = NCT6102D_WDT_CSR;
>>   		break;
>>   	case NCT6116_ID:
>> -		ret = nct6116;
>> +		val = superio_inb(0x21);
>> +		if (val == NCT6126_VER_A_LOW_ID || val == NCT6126_VER_B_LOW_ID)
>> +			ret = nct6126;
>> +		else
>> +			ret = nct6116;
>> +
>>   		cr_wdt_timeout = NCT6102D_WDT_TIMEOUT;
>>   		cr_wdt_control = NCT6102D_WDT_CONTROL;
>>   		cr_wdt_csr = NCT6102D_WDT_CSR;
>> @@ -499,6 +507,7 @@ static int __init wdt_init(void)
>>   		"NCT6796",
>>   		"NCT6102",
>>   		"NCT6116",
>> +		"NCT6126"
>>   	};
>>   
>>   	/* Apply system-specific quirks */
>> 

Paul.




-- 
Paul Louvel, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com