Hi Guenter, Andrew,

On 7/7/25 5:55 PM, Guenter Roeck wrote:

On Mon, Jul 07, 2025 at 04:49:31PM -0500, Andrew Davis wrote:

quoted

On 7/7/25 3:58 PM, Guenter Roeck wrote:

quoted

On Mon, Jul 07, 2025 at 01:00:02PM -0500, Judith Mendez wrote:

quoted

This allows to configure reaction between NMI and reset for WWD.

On K3 SoC's other than AM62L SoC [0], watchdog reset output is routed
to the ESM module which can subsequently route the signal to safety
master or SoC reset. On AM62L, the watchdog reset output is routed
to the SoC HW reset block. So, add a new compatible for AM62l to add
SoC data and configure reaction to reset instead of NMI.

[0] https://www.ti.com/product/AM62L
Signed-off-by: Judith Mendez <redacted>
---
   drivers/watchdog/rti_wdt.c | 32 ++++++++++++++++++++++++++++----
   1 file changed, 28 insertions(+), 4 deletions(-)

diff --git a/drivers/watchdog/rti_wdt.c b/drivers/watchdog/rti_wdt.c
index d1f9ce4100a8..c9ee443c70af 100644
--- a/drivers/watchdog/rti_wdt.c
+++ b/drivers/watchdog/rti_wdt.c

@@ -35,7 +35,8 @@
   #define RTIWWDRXCTRL	0xa4
   #define RTIWWDSIZECTRL	0xa8
-#define RTIWWDRX_NMI	0xa
+#define RTIWWDRXN_RST	0x5
+#define RTIWWDRXN_NMI	0xa
   #define RTIWWDSIZE_50P		0x50
   #define RTIWWDSIZE_25P		0x500

@@ -63,22 +64,29 @@
   static int heartbeat;
+struct rti_wdt_data {
+	bool reset;
+};
+
   /*
    * struct to hold data for each WDT device
    * @base - base io address of WD device
    * @freq - source clock frequency of WDT
    * @wdd  - hold watchdog device as is in WDT core
+ * @data - hold configuration data
    */
   struct rti_wdt_device {
   	void __iomem		*base;
   	unsigned long		freq;
   	struct watchdog_device	wdd;
+	const struct rti_wdt_data *data;
   };
   static int rti_wdt_start(struct watchdog_device *wdd)
   {
   	u32 timer_margin;
   	struct rti_wdt_device *wdt = watchdog_get_drvdata(wdd);
+	u8 reaction;
   	int ret;
   	ret = pm_runtime_resume_and_get(wdd->parent);

@@ -101,8 +109,13 @@ static int rti_wdt_start(struct watchdog_device *wdd)
   	 */
   	wdd->min_hw_heartbeat_ms = 520 * wdd->timeout + MAX_HW_ERROR;
-	/* Generate NMI when wdt expires */
-	writel_relaxed(RTIWWDRX_NMI, wdt->base + RTIWWDRXCTRL);
+	/* Reset device if wdt serviced outside of window or generate NMI if available */

Shouldn't that be "or generate NMI if _not_ available" ?

For almost all the K3 devices, the WDT has two selectable outputs, one resets
the device directly, the other is this "NMI" which is wired to an ESM module
which can take other actions (but usually it just also resets the device).
For AM62L that second NMI output is not wired (no ESM module), so our only
choice is to set the WDT to direct reset mode.

The wording is a little strange, but the "or generate NMI if available" meaning
if NMI is available, then do that. Reset being the fallback when _not_ available.

Maybe this would work better:

/* If WDT is serviced outside of window, generate NMI if available, or reset device */

The problem is that the code doesn't match the comment. The code checks the
"reset" flag and requests a reset if available. If doesn't check an "nmi"
flag.

If the preference is NMI, as your comment suggests, the flag should be named
"nmi" and be set if NMI is available. That would align the code and the
comment. Right now both code and comment are misleading, since the presence
of a reset flag (and setting it to false) suggests that a direct reset is
not available, and that reset is preferred if available. A reset is the
normally expected behavior for a watchdog, so the fact that this is _not_
the case for this watchdog should be made more visible.

How about:


/* If WWDT serviced outside of window, generate NMI or reset the device
if NMI not available */

if (wdt->data->reset)
	reaction = RTIWWDRXN_RST;
else
	reaction = RTIWWDRXN_NMI;

~ Judith

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