On 5/24/2018 9:19 AM, Guenter Roeck wrote:

On Wed, May 23, 2018 at 05:15:22PM -0700, Ray Jui wrote:

quoted

If the watchdog hardware is already enabled during the boot process,
when the Linux watchdog driver loads, it should reset the watchdog and
tell the watchdog framework. As a result, ping can be generated from
the watchdog framework, until the userspace watchdog daemon takes over
control

Signed-off-by: Ray Jui <redacted>
Reviewed-by: Vladimir Olovyannikov <redacted>
Reviewed-by: Scott Branden <scott.branden@broadcom.com>

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

I have one question, though: Is it really correct that both
INT_ENABLE _and_ RESET_ENABLE have to be set to enable the watdog ?
What if only RESET_ENABLE is set ?

According to the SP805 TRM, INT_ENABLE needs to be set to high to enable 
the counter and the interrupt. Counter will be stopped if INT_ENABLE is 
cleared. So yes, INT_ENABLE needs to be set.

Thanks,

Ray

Thanks,
Guenter

quoted

---
  drivers/watchdog/sp805_wdt.c | 19 +++++++++++++++++++
  1 file changed, 19 insertions(+)

diff --git a/drivers/watchdog/sp805_wdt.c b/drivers/watchdog/sp805_wdt.c
index 1484609..d662a6f 100644
--- a/drivers/watchdog/sp805_wdt.c
+++ b/drivers/watchdog/sp805_wdt.c

@@ -42,6 +42,7 @@
  	/* control register masks */
  	#define	INT_ENABLE	(1 << 0)
  	#define	RESET_ENABLE	(1 << 1)
+	#define	ENABLE_MASK	(INT_ENABLE | RESET_ENABLE)
  #define WDTINTCLR		0x00C
  #define WDTRIS			0x010
  #define WDTMIS			0x014

@@ -74,6 +75,15 @@ module_param(nowayout, bool, 0);
  MODULE_PARM_DESC(nowayout,
  		"Set to 1 to keep watchdog running after device release");
  
+/* returns true if wdt is running; otherwise returns false */
+static bool wdt_is_running(struct watchdog_device *wdd)
+{
+	struct sp805_wdt *wdt = watchdog_get_drvdata(wdd);
+	u32 wdtcontrol = readl_relaxed(wdt->base + WDTCONTROL);
+
+	return (wdtcontrol & ENABLE_MASK) == ENABLE_MASK;
+}
+
  /* This routine finds load value that will reset system in required timout */
  static int wdt_setload(struct watchdog_device *wdd, unsigned int timeout)
  {

@@ -239,6 +249,15 @@ sp805_wdt_probe(struct amba_device *adev, const struct amba_id *id)
  	watchdog_init_timeout(&wdt->wdd, 0, &adev->dev);
  	wdt_setload(&wdt->wdd, wdt->wdd.timeout);
  
+	/*
+	 * If HW is already running, enable/reset the wdt and set the running
+	 * bit to tell the wdt subsystem
+	 */
+	if (wdt_is_running(&wdt->wdd)) {
+		wdt_enable(&wdt->wdd);
+		set_bit(WDOG_HW_RUNNING, &wdt->wdd.status);
+	}
+
  	ret = watchdog_register_device(&wdt->wdd);
  	if (ret) {
  		dev_err(&adev->dev, "watchdog_register_device() failed: %d\n",

-- 
2.1.4

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