Add bootcount to AT91

Use AT91_GPBR 3 as a bootcount register.
The bootmagic and the bootcount shares AT91_GPBR 3.
Signed-off-by: NAnders Darander <ad@datarespons.se>

cpu/arm926ejs/at91/cpu.c

@@ -35,6 +35,13 @@
 #define CONFIG_SYS_AT91_MAIN_CLOCK 0
 #endif
 
+/*
+ * The at91sam9260 has 4 GPBR (0-3), we'll use the last one, nr 3,
+ * to keep track of the bootcount.
+ */
+#define AT91_GPBR_BOOTCOUNT_REGISTER 3
+#define AT91_BOOTCOUNT_ADDRESS (AT91_GPBR + 4*AT91_GPBR_BOOTCOUNT_REGISTER)
+
 int arch_cpu_init(void)
 {
 	return at91_clock_init(CONFIG_SYS_AT91_MAIN_CLOCK);
@@ -56,3 +63,30 @@ int print_cpuinfo(void)
 	return 0;
 }
 #endif
+
+#ifdef CONFIG_BOOTCOUNT_LIMIT
+/*
+ * Just as the mpc5xxx, we combine the BOOTCOUNT_MAGIC and boocount
+ * in one 32-bit register. This is done, as the AT91SAM9260 only has
+ * 4 GPBR.
+ */
+void bootcount_store (ulong a)
+{
+	volatile ulong *save_addr =
+		(volatile ulong *)(AT91_BASE_SYS + AT91_BOOTCOUNT_ADDRESS);
+
+	*save_addr = (BOOTCOUNT_MAGIC & 0xffff0000) | (a & 0x0000ffff);
+}
+
+ulong bootcount_load (void)
+{
+	volatile ulong *save_addr =
+		(volatile ulong *)(AT91_BASE_SYS + AT91_BOOTCOUNT_ADDRESS);
+
+	if ((*save_addr & 0xffff0000) != (BOOTCOUNT_MAGIC & 0xffff0000))
+		return 0;
+	else
+		return (*save_addr & 0x0000ffff);
+}
+
+#endif /* CONFIG_BOOTCOUNT_LIMIT */