[PATCH v2] watchdog: sp5100_tco: Add "action" module parameter

[PATCH v2] watchdog: sp5100_tco: Add "action" module parameter

[Vladimir Panteleev]

Allow configuring the "action" bit, as documented in [1].

Previously, the only action supported by this module was to reset the
system (0).  It can now be configured to power off (1) instead.

[1]: https://www.amd.com/system/files/TechDocs/44413.pdf

Signed-off-by: Vladimir Panteleev <git@vladimir.panteleev.md>
---

Changes since v1:
 - Drop the rename of the SP5100_WDT_ACTION_RESET define
 - Make the new parameter not visible in sysfs for consistency

 drivers/watchdog/sp5100_tco.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/watchdog/sp5100_tco.c b/drivers/watchdog/sp5100_tco.c
index ae54dd33e233..fb426b7d81da 100644
--- a/drivers/watchdog/sp5100_tco.c
+++ b/drivers/watchdog/sp5100_tco.c
@@ -65,6 +65,12 @@ static struct pci_dev *sp5100_tco_pci;
 
 /* module parameters */
 
+#define WATCHDOG_ACTION 0
+static bool action = WATCHDOG_ACTION;
+module_param(action, bool, 0);
+MODULE_PARM_DESC(action, "Action taken when watchdog expires, 0 to reset, 1 to poweroff (default="
+		 __MODULE_STRING(WATCHDOG_ACTION) ")");
+
 #define WATCHDOG_HEARTBEAT 60	/* 60 sec default heartbeat. */
 static int heartbeat = WATCHDOG_HEARTBEAT;  /* in seconds */
 module_param(heartbeat, int, 0);
@@ -297,8 +303,11 @@ static int sp5100_tco_timer_init(struct sp5100_tco *tco)
 	if (val & SP5100_WDT_FIRED)
 		wdd->bootstatus = WDIOF_CARDRESET;
 
-	/* Set watchdog action to reset the system */
-	val &= ~SP5100_WDT_ACTION_RESET;
+	/* Set watchdog action */
+	if (action)
+		val |= SP5100_WDT_ACTION_RESET;
+	else
+		val &= ~SP5100_WDT_ACTION_RESET;
 	writel(val, SP5100_WDT_CONTROL(tco->tcobase));
 
 	/* Set a reasonable heartbeat before we stop the timer */
-- 
2.37.3

Re: [PATCH v2] watchdog: sp5100_tco: Add "action" module parameter

[rwright]

On Tue, Sep 20, 2022 at 09:27:21AM +0000, Vladimir Panteleev wrote:
> Allow configuring the "action" bit, as documented in [1].
> 
> Previously, the only action supported by this module was to reset the
> system (0).  It can now be configured to power off (1) instead.
> 
> [1]: https://www.amd.com/system/files/TechDocs/44413.pdf

The referenced AMD document 44413 is over 10 years old, and I'm
concerned when I try to line that document up against the newer versions
that are implemented in AMD's EPYC processors, that the bit being
manipulated as SP5100_WDT_ACTION_RESET is effectively reserved in the
newer references, for example:

   https://www.amd.com/system/files/TechDocs/55772-A1-PUB.zip

Is Core::X86::Msr::CpuWdtCfg in the newer document is the same as
WatchDogControl in the cited 44413.pdf? If so, then I would point out
that bit 2 is now included in what is called, CpuWdtTimeBase where
values 2-3H are reserved,  meaning bit 2 effectively must be zero.

-- 
Randy Wright            Hewlett Packard Enterprise
Phone: (970) 898-0998   Mail: rwright@hpe.com

Re: [PATCH v2] watchdog: sp5100_tco: Add "action" module parameter

[Guenter Roeck]

On 9/22/22 10:36, rwright@hpe.com wrote:
> On Tue, Sep 20, 2022 at 09:27:21AM +0000, Vladimir Panteleev wrote:
>> Allow configuring the "action" bit, as documented in [1].
>>
>> Previously, the only action supported by this module was to reset the
>> system (0).  It can now be configured to power off (1) instead.
>>
>> [1]: https://www.amd.com/system/files/TechDocs/44413.pdf
> 
> The referenced AMD document 44413 is over 10 years old, and I'm
> concerned when I try to line that document up against the newer versions
> that are implemented in AMD's EPYC processors, that the bit being
> manipulated as SP5100_WDT_ACTION_RESET is effectively reserved in the
> newer references, for example:
> 
>     https://www.amd.com/system/files/TechDocs/55772-A1-PUB.zip
> 
> Is Core::X86::Msr::CpuWdtCfg in the newer document is the same as
> WatchDogControl in the cited 44413.pdf? If so, then I would point out
> that bit 2 is now included in what is called, CpuWdtTimeBase where
> values 2-3H are reserved,  meaning bit 2 effectively must be zero.
> 

I think those may be different watchdogs. Chapter 9.2.6 ("Watchdog
Timer (WDT) Registers") in 55772-A1-PUB still lists bit 2 of the
control register as:

WatchdogAction. Read-write. Reset: 0. 0=System reset. 1=System power off. This bit determines the action to
be taken when the watchdog timer expires. The bit is only valid when the watchdog is enabled.

Guenter

Re: [PATCH v2] watchdog: sp5100_tco: Add "action" module parameter

[Jerry Hoemann]

On Tue, Sep 20, 2022 at 09:27:21AM +0000, Vladimir Panteleev wrote:
> Allow configuring the "action" bit, as documented in [1].
> 
> Previously, the only action supported by this module was to reset the
> system (0).  It can now be configured to power off (1) instead.
> 
> [1]: https://www.amd.com/system/files/TechDocs/44413.pdf
> 
> Signed-off-by: Vladimir Panteleev <git@vladimir.panteleev.md>
> ---
> 
> Changes since v1:
>  - Drop the rename of the SP5100_WDT_ACTION_RESET define
>  - Make the new parameter not visible in sysfs for consistency
> 
>  drivers/watchdog/sp5100_tco.c | 13 +++++++++++--
>  1 file changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/watchdog/sp5100_tco.c b/drivers/watchdog/sp5100_tco.c
> index ae54dd33e233..fb426b7d81da 100644
> --- a/drivers/watchdog/sp5100_tco.c
> +++ b/drivers/watchdog/sp5100_tco.c
> @@ -65,6 +65,12 @@ static struct pci_dev *sp5100_tco_pci;
>  
>  /* module parameters */
>  
> +#define WATCHDOG_ACTION 0
> +static bool action = WATCHDOG_ACTION;
> +module_param(action, bool, 0);
> +MODULE_PARM_DESC(action, "Action taken when watchdog expires, 0 to reset, 1 to poweroff (default="
> +		 __MODULE_STRING(WATCHDOG_ACTION) ")");
> +
>  #define WATCHDOG_HEARTBEAT 60	/* 60 sec default heartbeat. */
>  static int heartbeat = WATCHDOG_HEARTBEAT;  /* in seconds */
>  module_param(heartbeat, int, 0);
> @@ -297,8 +303,11 @@ static int sp5100_tco_timer_init(struct sp5100_tco *tco)
>  	if (val & SP5100_WDT_FIRED)
>  		wdd->bootstatus = WDIOF_CARDRESET;
>  
> -	/* Set watchdog action to reset the system */
> -	val &= ~SP5100_WDT_ACTION_RESET;
> +	/* Set watchdog action */
> +	if (action)
> +		val |= SP5100_WDT_ACTION_RESET;
> +	else
> +		val &= ~SP5100_WDT_ACTION_RESET;
>  	writel(val, SP5100_WDT_CONTROL(tco->tcobase));
>  
>  	/* Set a reasonable heartbeat before we stop the timer */
> -- 
> 2.37.3

Looking at other WDT,  I see at least three  that have an "action"
parameter.  These appear to have inconsistent semantics with each 
other and this patch.

Is there something we could to create more uniformity with module
level parameters like these?


Examples:

machzwd.c:
MODULE_PARM_DESC(action, "after watchdog resets, generate: "
                                "0 = RESET(*)  1 = SMI  2 = NMI  3 = SCI");

pseries-wdt.c
static const unsigned long pseries_wdt_action[] = {
        [0] = PSERIES_WDTF_ACTION_HARD_POWEROFF,
	[1] = PSERIES_WDTF_ACTION_HARD_RESTART,
	[2] = PSERIES_WDTF_ACTION_DUMP_RESTART,

sbsa_gwdt.c
MODULE_PARM_DESC(action, "after watchdog gets WS0 interrupt, do: "
                 "0 = skip(*)  1 = panic");


-- 

-----------------------------------------------------------------------------
Jerry Hoemann                  Software Engineer   Hewlett Packard Enterprise
-----------------------------------------------------------------------------

Re: [PATCH v2] watchdog: sp5100_tco: Add "action" module parameter

[Guenter Roeck]

On Tue, Sep 20, 2022 at 09:27:21AM +0000, Vladimir Panteleev wrote:
> Allow configuring the "action" bit, as documented in [1].
> 
> Previously, the only action supported by this module was to reset the
> system (0).  It can now be configured to power off (1) instead.
> 
> [1]: https://www.amd.com/system/files/TechDocs/44413.pdf
> 
> Signed-off-by: Vladimir Panteleev <git@vladimir.panteleev.md>

Reviewed-by: Guenter Roeck <linux@roeck-us.net>

> ---
> 
> Changes since v1:
>  - Drop the rename of the SP5100_WDT_ACTION_RESET define
>  - Make the new parameter not visible in sysfs for consistency
> 
>  drivers/watchdog/sp5100_tco.c | 13 +++++++++++--
>  1 file changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/watchdog/sp5100_tco.c b/drivers/watchdog/sp5100_tco.c
> index ae54dd33e233..fb426b7d81da 100644
> --- a/drivers/watchdog/sp5100_tco.c
> +++ b/drivers/watchdog/sp5100_tco.c
> @@ -65,6 +65,12 @@ static struct pci_dev *sp5100_tco_pci;
>  
>  /* module parameters */
>  
> +#define WATCHDOG_ACTION 0
> +static bool action = WATCHDOG_ACTION;
> +module_param(action, bool, 0);
> +MODULE_PARM_DESC(action, "Action taken when watchdog expires, 0 to reset, 1 to poweroff (default="
> +		 __MODULE_STRING(WATCHDOG_ACTION) ")");
> +
>  #define WATCHDOG_HEARTBEAT 60	/* 60 sec default heartbeat. */
>  static int heartbeat = WATCHDOG_HEARTBEAT;  /* in seconds */
>  module_param(heartbeat, int, 0);
> @@ -297,8 +303,11 @@ static int sp5100_tco_timer_init(struct sp5100_tco *tco)
>  	if (val & SP5100_WDT_FIRED)
>  		wdd->bootstatus = WDIOF_CARDRESET;
>  
> -	/* Set watchdog action to reset the system */
> -	val &= ~SP5100_WDT_ACTION_RESET;
> +	/* Set watchdog action */
> +	if (action)
> +		val |= SP5100_WDT_ACTION_RESET;
> +	else
> +		val &= ~SP5100_WDT_ACTION_RESET;
>  	writel(val, SP5100_WDT_CONTROL(tco->tcobase));
>  
>  	/* Set a reasonable heartbeat before we stop the timer */
> -- 
> 2.37.3
>