gt64xxx: access right I/O port when activating byte swapping

index 10fcca3..39dd8ff 100644
@@ -176,6 +176,7 @@
 
 /* PCI Internal */
 #define GT_PCI0_CMD    		(0xc00 >> 2)
+#define   GT_CMD_MWORDSWAP      (1 << 10)
 #define GT_PCI0_TOR    		(0xc04 >> 2)
 #define GT_PCI0_BS_SCS10    	(0xc08 >> 2)
 #define GT_PCI0_BS_SCS32    	(0xc0c >> 2)

@@ -292,6 +293,62 @@ static void gt64120_isd_mapping(GT64120State *s)
     memory_region_add_subregion(get_system_memory(), s->ISD_start, &s->ISD_mem);
 }
 
+static uint64_t gt64120_pci_io_read(void *opaque, hwaddr addr,
+                                    unsigned int size)
+{
+    GT64120State *s = opaque;
+    uint8_t buf[4];
+
+    if (s->regs[GT_PCI0_CMD] & GT_CMD_MWORDSWAP) {
+        addr = (addr & ~3) + 4 - size - (addr & 3);
+    }
+
+    address_space_read(&address_space_io, addr, MEMTXATTRS_UNSPECIFIED,
+                       buf, size);
+
+    if (size == 1) {
+        return buf[0];
+    } else if (size == 2) {
+        return lduw_le_p(buf);
+    } else if (size == 4) {
+        return ldl_le_p(buf);
+    } else {
+        g_assert_not_reached();
+    }
+}
+
+static void gt64120_pci_io_write(void *opaque, hwaddr addr, uint64_t data,
+                                 unsigned int size)
+{
+    GT64120State *s = opaque;
+    uint8_t buf[4];
+
+    if (s->regs[GT_PCI0_CMD] & GT_CMD_MWORDSWAP) {
+        addr = (addr & ~3) + 4 - size - (addr & 3);
+    }
+
+    if (size == 1) {
+        buf[0] = data;
+    } else if (size == 2) {
+        stw_le_p(buf, data);
+    } else if (size == 4) {
+        stl_le_p(buf, data);
+    } else {
+        g_assert_not_reached();
+    }
+
+    address_space_write(&address_space_io, addr, MEMTXATTRS_UNSPECIFIED,
+                        buf, size);
+}
+
+static const MemoryRegionOps gt64120_pci_io_ops = {
+    .read = gt64120_pci_io_read,
+    .write = gt64120_pci_io_write,
+    .endianness = DEVICE_LITTLE_ENDIAN,
+    .impl.max_access_size = 4,
+    .valid.unaligned = true,
+};
+
 static void gt64120_pci_mapping(GT64120State *s)
 {
     /* Update PCI0IO mapping */

@@ -306,8 +363,9 @@ static void gt64120_pci_mapping(GT64120State *s)
         s->PCI0IO_length = ((s->regs[GT_PCI0IOHD] + 1) -
                             (s->regs[GT_PCI0IOLD] & 0x7f)) << 21;
         if (s->PCI0IO_length) {
-            memory_region_init_alias(&s->PCI0IO_mem, OBJECT(s), "pci0-io",
-                                     get_system_io(), 0, s->PCI0IO_length);
+            memory_region_init_io(&s->PCI0IO_mem, OBJECT(s),
+                                  &gt64120_pci_io_ops,
+                                  s, "pci0-io", s->PCI0IO_length);
             memory_region_add_subregion(get_system_memory(), s->PCI0IO_start,
                                         &s->PCI0IO_mem);
         }