watchdog: imx: add config to disable wdog reset

Add Kconfig option WATCHDOG_RESET_DISABLE to disable watchdog reset
in imx_watchdog driver, so that the watchdog will not be fed in
u-boot if CONFIG_WATCHDOG_RESET_DISABLE is enabled.

Signed-off-by: Xiaoliang Yang <xiaoliang.yang_1@nxp.com>

arch/arm/cpu/armv8/fsl-layerscape/doc/README.lsch2

@@ -17,3 +17,5 @@ Use following config to set watchdog timeout, if this config is not defined,
 the default timeout value is 128s which is the maximum. Set 10 seconds for
 example:
     #define CONFIG_WATCHDOG_TIMEOUT_MSECS 10000
+Set CONFIG_WATCHDOG_RESET_DISABLE to disable reset watchdog, so that the
+watchdog will not be fed in u-boot.

drivers/watchdog/Kconfig

@@ -11,6 +11,12 @@ config WATCHDOG
 config HW_WATCHDOG
 	bool
 
+config WATCHDOG_RESET_DISABLE
+	bool "Disable reset watchdog"
+	help
+	   Disable reset watchdog, which can let WATCHDOG_RESET invalid, so
+	   that the watchdog will not be fed in u-boot.
+
 config BCM2835_WDT
 	bool "Enable BCM2835/2836 watchdog driver"
 	select HW_WATCHDOG

drivers/watchdog/imx_watchdog.c

@@ -16,10 +16,12 @@
 #ifdef CONFIG_IMX_WATCHDOG
 void hw_watchdog_reset(void)
 {
+#ifndef CONFIG_WATCHDOG_RESET_DISABLE
 	struct watchdog_regs *wdog = (struct watchdog_regs *)WDOG1_BASE_ADDR;
 
 	writew(0x5555, &wdog->wsr);
 	writew(0xaaaa, &wdog->wsr);
+#endif /* CONFIG_WATCHDOG_RESET_DISABLE*/
 }
 
 void hw_watchdog_init(void)