[PATCH v3] mac_oldworld: Add machine ID register

[BALATON Zoltan]

The G3 beige machine has a machine ID register that is accessed by the
firmware to deternine the board config. Add basic emulation of it.

Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
---
v3: add empty write function in case anything tries to write reg

hw/ppc/mac_oldworld.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/hw/ppc/mac_oldworld.c b/hw/ppc/mac_oldworld.c
index 3812adc441..acaf468458 100644
--- a/hw/ppc/mac_oldworld.c
+++ b/hw/ppc/mac_oldworld.c
@@ -80,6 +80,22 @@ static void ppc_heathrow_reset(void *opaque)
     cpu_reset(CPU(cpu));
 }

+static uint64_t machine_id_read(void *opaque, hwaddr addr, unsigned size)
+{
+    return (addr == 0 && size == 2 ? 0x3d8c : 0);
+}
+
+static void machine_id_write(void *opaque, hwaddr addr,
+                             uint64_t val, unsigned size)
+{
+    return;
+}
+
+const MemoryRegionOps machine_id_reg_ops = {
+    .read = machine_id_read,
+    .write = machine_id_write,
+};
+
 static void ppc_heathrow_init(MachineState *machine)
 {
     ram_addr_t ram_size = machine->ram_size;
@@ -93,6 +109,7 @@ static void ppc_heathrow_init(MachineState *machine)
     char *filename;
     int linux_boot, i;
     MemoryRegion *bios = g_new(MemoryRegion, 1);
+    MemoryRegion *machine_id = g_new(MemoryRegion, 1);
     uint32_t kernel_base, initrd_base, cmdline_base = 0;
     int32_t kernel_size, initrd_size;
     PCIBus *pci_bus;
@@ -227,6 +244,10 @@ static void ppc_heathrow_init(MachineState *machine)
         }
     }

+    memory_region_init_io(machine_id, OBJECT(machine), &machine_id_reg_ops,
+                          NULL, "machine_id", 2);
+    memory_region_add_subregion(get_system_memory(), 0xff000004, machine_id);
+
     /* XXX: we register only 1 output pin for heathrow PIC */
     pic_dev = qdev_create(NULL, TYPE_HEATHROW);
     qdev_init_nofail(pic_dev);
-- 
2.21.3