diff --git a/hw/arm/mps2-tz.c b/hw/arm/mps2-tz.c
index 746ba3cc59e..f40e854dec7 100644
--- a/hw/arm/mps2-tz.c
+++ b/hw/arm/mps2-tz.c
@@ -375,6 +375,7 @@ static qemu_irq get_sse_irq_in(MPS2TZMachineState *mms, int irqno)
 
 /* Union describing the device-specific extra data we pass to the devfn. */
 typedef union PPCExtraData {
+    bool i2c_internal;
 } PPCExtraData;
 
 /* Most of the devices in the AN505 FPGA image sit behind
@@ -711,6 +712,20 @@ static MemoryRegion *make_i2c(MPS2TZMachineState *mms, void *opaque,
     object_initialize_child(OBJECT(mms), name, i2c, TYPE_ARM_SBCON_I2C);
     s = SYS_BUS_DEVICE(i2c);
     sysbus_realize(s, &error_fatal);
+
+    /*
+     * If this is an internal-use-only i2c bus, mark it full
+     * so that user-created i2c devices are not plugged into it.
+     * If we implement models of any on-board i2c devices that
+     * plug in to one of the internal-use-only buses, then we will
+     * need to create and plugging those in here before we mark the
+     * bus as full.
+     */
+    if (extradata->i2c_internal) {
+        BusState *qbus = qdev_get_child_bus(DEVICE(i2c), "i2c");
+        qbus_mark_full(qbus);
+    }
+
     return sysbus_mmio_get_region(s, 0);
 }
 
@@ -921,10 +936,14 @@ static void mps2tz_common_init(MachineState *machine)
                 { "uart2", make_uart, &mms->uart[2], 0x40202000, 0x1000, { 36, 37, 44 } },
                 { "uart3", make_uart, &mms->uart[3], 0x40203000, 0x1000, { 38, 39, 45 } },
                 { "uart4", make_uart, &mms->uart[4], 0x40204000, 0x1000, { 40, 41, 46 } },
-                { "i2c0", make_i2c, &mms->i2c[0], 0x40207000, 0x1000 },
-                { "i2c1", make_i2c, &mms->i2c[1], 0x40208000, 0x1000 },
-                { "i2c2", make_i2c, &mms->i2c[2], 0x4020c000, 0x1000 },
-                { "i2c3", make_i2c, &mms->i2c[3], 0x4020d000, 0x1000 },
+                { "i2c0", make_i2c, &mms->i2c[0], 0x40207000, 0x1000, {},
+                  { .i2c_internal = true /* touchscreen */ } },
+                { "i2c1", make_i2c, &mms->i2c[1], 0x40208000, 0x1000, {},
+                  { .i2c_internal = true /* audio conf */ } },
+                { "i2c2", make_i2c, &mms->i2c[2], 0x4020c000, 0x1000, {},
+                  { .i2c_internal = false /* shield 0 */ } },
+                { "i2c3", make_i2c, &mms->i2c[3], 0x4020d000, 0x1000, {},
+                  { .i2c_internal = false /* shield 1 */ } },
             },
         }, {
             .name = "apb_ppcexp2",
@@ -965,15 +984,20 @@ static void mps2tz_common_init(MachineState *machine)
         }, {
             .name = "apb_ppcexp1",
             .ports = {
-                { "i2c0", make_i2c, &mms->i2c[0], 0x41200000, 0x1000 },
-                { "i2c1", make_i2c, &mms->i2c[1], 0x41201000, 0x1000 },
+                { "i2c0", make_i2c, &mms->i2c[0], 0x41200000, 0x1000, {},
+                  { .i2c_internal = true /* touchscreen */ } },
+                { "i2c1", make_i2c, &mms->i2c[1], 0x41201000, 0x1000, {},
+                  { .i2c_internal = true /* audio conf */ } },
                 { "spi0", make_spi, &mms->spi[0], 0x41202000, 0x1000, { 52 } },
                 { "spi1", make_spi, &mms->spi[1], 0x41203000, 0x1000, { 53 } },
                 { "spi2", make_spi, &mms->spi[2], 0x41204000, 0x1000, { 54 } },
-                { "i2c2", make_i2c, &mms->i2c[2], 0x41205000, 0x1000 },
-                { "i2c3", make_i2c, &mms->i2c[3], 0x41206000, 0x1000 },
+                { "i2c2", make_i2c, &mms->i2c[2], 0x41205000, 0x1000, {},
+                  { .i2c_internal = false /* shield 0 */ } },
+                { "i2c3", make_i2c, &mms->i2c[3], 0x41206000, 0x1000, {},
+                  { .i2c_internal = false /* shield 1 */ } },
                 { /* port 7 reserved */ },
-                { "i2c4", make_i2c, &mms->i2c[4], 0x41208000, 0x1000 },
+                { "i2c4", make_i2c, &mms->i2c[4], 0x41208000, 0x1000, {},
+                  { .i2c_internal = true /* DDR4 EEPROM */ } },
             },
         }, {
             .name = "apb_ppcexp2",
@@ -1015,15 +1039,20 @@ static void mps2tz_common_init(MachineState *machine)
         }, {
             .name = "apb_ppcexp1",
             .ports = {
-                { "i2c0", make_i2c, &mms->i2c[0], 0x49200000, 0x1000 },
-                { "i2c1", make_i2c, &mms->i2c[1], 0x49201000, 0x1000 },
+                { "i2c0", make_i2c, &mms->i2c[0], 0x49200000, 0x1000, {},
+                  { .i2c_internal = true /* touchscreen */ } },
+                { "i2c1", make_i2c, &mms->i2c[1], 0x49201000, 0x1000, {},
+                  { .i2c_internal = true /* audio conf */ } },
                 { "spi0", make_spi, &mms->spi[0], 0x49202000, 0x1000, { 53 } },
                 { "spi1", make_spi, &mms->spi[1], 0x49203000, 0x1000, { 54 } },
                 { "spi2", make_spi, &mms->spi[2], 0x49204000, 0x1000, { 55 } },
-                { "i2c2", make_i2c, &mms->i2c[2], 0x49205000, 0x1000 },
-                { "i2c3", make_i2c, &mms->i2c[3], 0x49206000, 0x1000 },
+                { "i2c2", make_i2c, &mms->i2c[2], 0x49205000, 0x1000, {},
+                  { .i2c_internal = false /* shield 0 */ } },
+                { "i2c3", make_i2c, &mms->i2c[3], 0x49206000, 0x1000, {},
+                  { .i2c_internal = false /* shield 1 */ } },
                 { /* port 7 reserved */ },
-                { "i2c4", make_i2c, &mms->i2c[4], 0x49208000, 0x1000 },
+                { "i2c4", make_i2c, &mms->i2c[4], 0x49208000, 0x1000, {},
+                  { .i2c_internal = true /* DDR4 EEPROM */ } },
             },
         }, {
             .name = "apb_ppcexp2",
