On Thu, Jun 4, 2015 at 3:15 PM, Tim Harvey [off-list ref] wrote:

+       /* Generate internal chip-level reset if WDOG times out */
+       if (!wdev->ext_reset)
+               val &= ~IMX2_WDT_WCR_WRE;
+       /* Or if external-reset assert WDOG_B reset only on time-out */
+       else
+               val |= IMX2_WDT_WCR_WRE;

I think you can always enable IMX2_WDT_WCR_WRE.
So needn't ext_reset.

If you don't config WDOG_B pin mux,  WDOG_B do nothing.

best regards
Frank Li