watchdog: imx_wdt: add variable timeout support

- Current driver only allows to define a fixed timeout value in the
  board config file.
- Extend 'imx_watchdog_init' parameter list with timeout value as
  received by 'imx_wdt_start' function. Calculate timeout value and
  write appropriate value into WCR register.
- For legacy use, the fixed CONFIG_WATCHDOG_TIMEOUT_MSECS from board
  config is still evaluated.
Signed-off-by: Thomas Schaefer <thomas.schaefer@kontron.com>

drivers/watchdog/imx_watchdog.c

@@ -57,9 +57,8 @@ static void imx_watchdog_reset(struct watchdog_regs *wdog)
 #endif /* CONFIG_WATCHDOG_RESET_DISABLE*/
 }
 
-static void imx_watchdog_init(struct watchdog_regs *wdog, bool ext_reset)
+static void imx_watchdog_init(u64 timeout, struct watchdog_regs *wdog, bool ext_reset)
 {
-	u16 timeout;
 	u16 wcr;
 
 	/*
@@ -67,10 +66,14 @@ static void imx_watchdog_init(struct watchdog_regs *wdog, bool ext_reset)
 	 * 0.5 and 128 Seconds. If not defined
 	 * in configuration file, sets 128 Seconds
 	 */
+	if (timeout != 0) {
+		timeout = (timeout / 500) - 1;
+	} else {
 #ifndef CONFIG_WATCHDOG_TIMEOUT_MSECS
 #define CONFIG_WATCHDOG_TIMEOUT_MSECS 128000
 #endif
-	timeout = (CONFIG_WATCHDOG_TIMEOUT_MSECS / 500) - 1;
+		timeout = (CONFIG_WATCHDOG_TIMEOUT_MSECS / 500) - 1;
+	}
 #ifdef CONFIG_FSL_LSCH2
 	wcr = (WCR_WDA | WCR_SRS | WCR_WDE) << 8 | timeout;
 #else
@@ -95,7 +98,7 @@ void hw_watchdog_init(void)
 {
 	struct watchdog_regs *wdog = (struct watchdog_regs *)WDOG1_BASE_ADDR;
 
-	imx_watchdog_init(wdog, true);
+	imx_watchdog_init(0, wdog, true);
 }
 #else
 struct imx_wdt_priv {
@@ -126,7 +129,7 @@ static int imx_wdt_start(struct udevice *dev, u64 timeout, ulong flags)
 {
 	struct imx_wdt_priv *priv = dev_get_priv(dev);
 
-	imx_watchdog_init(priv->base, priv->ext_reset);
+	imx_watchdog_init(timeout, priv->base, priv->ext_reset);
 
 	return 0;
 }