AT91: reset.c: fix comments, add option

Signed-off-by: Reinhard Meyer <u-boot@emk-elektronik.de>

arch/arm/cpu/arm926ejs/at91/reset.c

@@ -27,18 +27,19 @@
 #include <asm/arch/at91_rstc.h>
 #include <asm/arch/io.h>
 
-/*
- * Reset the cpu by setting up the watchdog timer and let him time out.
- */
+/* Reset the cpu by telling the reset controller to do so */
 void reset_cpu(ulong ignored)
 {
 	at91_rstc_t *rstc = (at91_rstc_t *) AT91_RSTC_BASE;
 
-	/* this is the way Linux does it */
-
-	writel(AT91_RSTC_KEY | AT91_RSTC_CR_PROCRST | AT91_RSTC_CR_PERRST,
-		&rstc->cr);
-
-	while (1);
-	/* Never reached */
+	writel(AT91_RSTC_KEY
+		| AT91_RSTC_CR_PROCRST	/* Processor Reset */
+		| AT91_RSTC_CR_PERRST	/* Peripheral Reset */
+#ifdef CONFIG_AT91RESET_EXTRST
+		| AT91_RSTC_CR_EXTRST	/* External Reset (assert nRST pin) */
+#endif
+		, &rstc->cr);
+	/* never reached */
+	while (1)
+		;
 }