arm_boot: support board IDs more than 16 bits wide

Support passing a board ID value to the kernel in r1
that is more than 16 bits wide. This is needed to pass
the '-1 == invalid' value for boards which only support
device tree booting.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Tested-by: Mark Langsdorf <mark.langsdorf@calxeda.com>

hw/arm_boot.c

@@ -20,10 +20,10 @@
 /* The worlds second smallest bootloader.  Set r0-r2, then jump to kernel.  */
 static uint32_t bootloader[] = {
   0xe3a00000, /* mov     r0, #0 */
-  0xe3a01000, /* mov     r1, #0x?? */
-  0xe3811c00, /* orr     r1, r1, #0x??00 */
-  0xe59f2000, /* ldr     r2, [pc, #0] */
-  0xe59ff000, /* ldr     pc, [pc, #0] */
+  0xe59f1004, /* ldr     r1, [pc, #4] */
+  0xe59f2004, /* ldr     r2, [pc, #4] */
+  0xe59ff004, /* ldr     pc, [pc, #4] */
+  0, /* Board ID */
   0, /* Address of kernel args.  Set by integratorcp_init.  */
   0  /* Kernel entry point.  Set by integratorcp_init.  */
 };
@@ -301,8 +301,7 @@ void arm_load_kernel(CPUState *env, struct arm_boot_info *info)
         } else {
             initrd_size = 0;
         }
-        bootloader[1] |= info->board_id & 0xff;
-        bootloader[2] |= (info->board_id >> 8) & 0xff;
+        bootloader[4] = info->board_id;
         bootloader[5] = info->loader_start + KERNEL_ARGS_ADDR;
         bootloader[6] = entry;
         for (n = 0; n < sizeof(bootloader) / 4; n++) {