AVR32: Must add NOPs after disabling interrupts for AT32UC3A0512ES

The AT32UC3A0512ES chip has a bug when disabling interrupts. As a
workaround, two NOPs can be inserted.

Signed-off-by: Gunnar Rangoy <gunnar@rangoy.com>
Signed-off-by: Paul Driveklepp <pauldriveklepp@gmail.com>
Signed-off-by: Olav Morken <olavmrk@gmail.com>
Signed-off-by: Haavard Skinnemoen <haavard.skinnemoen@atmel.com>

lib_avr32/interrupts.c

@@ -35,5 +35,12 @@ int disable_interrupts(void)
 	sr = sysreg_read(SR);
 	asm volatile("ssrf	%0" : : "n"(SYSREG_GM_OFFSET));
 
+#ifdef CONFIG_AT32UC3A0xxx
+	/* Two NOPs are required after masking interrupts on the
+	 * AT32UC3A0512ES. See errata 41.4.5.5. */
+	asm("nop");
+	asm("nop");
+#endif
+
 	return !SYSREG_BFEXT(GM, sr);
 }