arm: Stub out NRF51 TWI magnetometer/accelerometer detection

Recent microbit firmwares panic if the TWI magnetometer/accelerometer
devices are not detected during startup.  We don't implement TWI (I2C)
so let's stub out these devices just to let the firmware boot.

Signed-off by: Steffen Görtz <contrib@steffen-goertz.de>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20190110094020.18354-2-stefanha@redhat.com
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
[PMM: fixed comment style]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 16 insertions, 0 deletions

diff --git a/hw/arm/microbit.c b/hw/arm/microbit.c
index a734e7f650..da67bf6d9d 100644
--- a/hw/arm/microbit.c
+++ b/hw/arm/microbit.c
@@ -16,11 +16,13 @@
 #include "exec/address-spaces.h"
 
 #include "hw/arm/nrf51_soc.h"
+#include "hw/i2c/microbit_i2c.h"
 
 typedef struct {
     MachineState parent;
 
     NRF51State nrf51;
+    MicrobitI2CState i2c;
 } MicrobitMachineState;
 
 #define TYPE_MICROBIT_MACHINE MACHINE_TYPE_NAME("microbit")
@@ -32,7 +34,9 @@ static void microbit_init(MachineState *machine)
 {
     MicrobitMachineState *s = MICROBIT_MACHINE(machine);
     MemoryRegion *system_memory = get_system_memory();
+    MemoryRegion *mr;
     Object *soc = OBJECT(&s->nrf51);
+    Object *i2c = OBJECT(&s->i2c);
 
     sysbus_init_child_obj(OBJECT(machine), "nrf51", soc, sizeof(s->nrf51),
                           TYPE_NRF51_SOC);
@@ -41,6 +45,18 @@ static void microbit_init(MachineState *machine)
                              &error_fatal);
     object_property_set_bool(soc, true, "realized", &error_fatal);
 
+    /*
+     * Overlap the TWI stub device into the SoC.  This is a microbit-specific
+     * hack until we implement the nRF51 TWI controller properly and the
+     * magnetometer/accelerometer devices.
+     */
+    sysbus_init_child_obj(OBJECT(machine), "microbit.twi", i2c,
+                          sizeof(s->i2c), TYPE_MICROBIT_I2C);
+    object_property_set_bool(i2c, true, "realized", &error_fatal);
+    mr = sysbus_mmio_get_region(SYS_BUS_DEVICE(i2c), 0);
+    memory_region_add_subregion_overlap(&s->nrf51.container, NRF51_TWI_BASE,
+                                        mr, -1);
+
     armv7m_load_kernel(ARM_CPU(first_cpu), machine->kernel_filename,
                        NRF51_SOC(soc)->flash_size);
 }