[PATCH] watchdog: rti: support SPL (or re-start)

[A. Sverdlin]

From: Alexander Sverdlin <alexander.sverdlin at siemens.com>

If the RTI watchdog has been enabled in SPL, enabling it in U-Boot proper
fails because it can only be enabled once in HW and never stopped. This
however leads to a situation that wdt_cyclic() watchdog trigger is not
being started any longer and the WDT fires at some point.

Allow for WDT re-start by not bailing out if the [previously] configured
period matches the one to be configured.

Enabling in [A53] SPL has been tested on AM62x-based HW (where [A53] SPL is
responsible for loading R5 DM firmware and not this driver).

Signed-off-by: Alexander Sverdlin <alexander.sverdlin at siemens.com>
---
 drivers/watchdog/rti_wdt.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/watchdog/rti_wdt.c b/drivers/watchdog/rti_wdt.c
index 99168d0cad03..320c5ca19e0a 100644
--- a/drivers/watchdog/rti_wdt.c
+++ b/drivers/watchdog/rti_wdt.c
@@ -131,18 +131,19 @@ static int rti_wdt_start(struct udevice *dev, u64 timeout_ms, ulong flags)
 	u32 timer_margin;
 	int ret;
 
-	if (readl(priv->regs + RTIDWDCTRL) == WDENABLE_KEY)
+	timer_margin = timeout_ms * priv->clk_hz / 1000;
+	timer_margin >>= WDT_PRELOAD_SHIFT;
+	if (timer_margin > WDT_PRELOAD_MAX)
+		timer_margin = WDT_PRELOAD_MAX;
+
+	if (readl(priv->regs + RTIDWDCTRL) == WDENABLE_KEY &&
+	    readl(priv->regs + RTIDWDPRLD) != timer_margin)
 		return -EBUSY;
 
 	ret = rti_wdt_load_fw(dev);
 	if (ret < 0)
 		return ret;
 
-	timer_margin = timeout_ms * priv->clk_hz / 1000;
-	timer_margin >>= WDT_PRELOAD_SHIFT;
-	if (timer_margin > WDT_PRELOAD_MAX)
-		timer_margin = WDT_PRELOAD_MAX;
-
 	writel(timer_margin, priv->regs + RTIDWDPRLD);
 	writel(RTIWWDRX_NMI, priv->regs + RTIWWDRXCTRL);
 	writel(RTIWWDSIZE_50P, priv->regs + RTIWWDSIZECTRL);
-- 
2.47.0