hw/i2c/microbit_i2c.c

   1 /*
   2  * Microbit stub for Nordic Semiconductor nRF51 SoC Two-Wire Interface
   3  * http://infocenter.nordicsemi.com/pdf/nRF51_RM_v3.0.1.pdf
   4  *
   5  * This is a microbit-specific stub for the TWI controller on the nRF51 SoC.
   6  * We don't emulate I2C devices but the firmware probes the
   7  * accelerometer/magnetometer on startup and panics if they are not found.
   8  * Therefore we stub out the probing.
   9  *
  10  * In the future this file could evolve into a full nRF51 TWI controller
  11  * device.
  12  *
  13  * Copyright 2018 Steffen Görtz <contrib@steffen-goertz.de>
  14  * Copyright 2019 Red Hat, Inc.
  15  *
  16  * This code is licensed under the GPL version 2 or later.  See
  17  * the COPYING file in the top-level directory.
  18  */
  19
  20 #include "qemu/osdep.h"
  21 #include "qemu/log.h"
  22 #include "qemu/module.h"
  23 #include "hw/i2c/microbit_i2c.h"
  24 #include "migration/vmstate.h"
  25
  26 static const uint32_t twi_read_sequence[] = {0x5A, 0x5A, 0x40};
  27
  28 static uint64_t microbit_i2c_read(void *opaque, hwaddr addr, unsigned int size)
  29 {
  30     MicrobitI2CState *s = opaque;
  31     uint64_t data = 0x00;
  32
  33     switch (addr) {
  34     case NRF51_TWI_EVENT_STOPPED:
  35         data = 0x01;
  36         break;
  37     case NRF51_TWI_EVENT_RXDREADY:
  38         data = 0x01;
  39         break;
  40     case NRF51_TWI_EVENT_TXDSENT:
  41         data = 0x01;
  42         break;
  43     case NRF51_TWI_REG_RXD:
  44         data = twi_read_sequence[s->read_idx];
  45         if (s->read_idx < G_N_ELEMENTS(twi_read_sequence)) {
  46             s->read_idx++;
  47         }
  48         break;
  49     default:
  50         data = s->regs[addr / sizeof(s->regs[0])];
  51         break;
  52     }
  53
  54     qemu_log_mask(LOG_UNIMP, "%s: 0x%" HWADDR_PRIx " [%u] = %" PRIx32 "\n",
  55                   __func__, addr, size, (uint32_t)data);
  56
  57
  58     return data;
  59 }
  60
  61 static void microbit_i2c_write(void *opaque, hwaddr addr, uint64_t data,
  62                                unsigned int size)
  63 {
  64     MicrobitI2CState *s = opaque;
  65
  66     qemu_log_mask(LOG_UNIMP, "%s: 0x%" HWADDR_PRIx " <- 0x%" PRIx64 " [%u]\n",
  67                   __func__, addr, data, size);
  68     s->regs[addr / sizeof(s->regs[0])] = data;
  69 }
  70
  71 static const MemoryRegionOps microbit_i2c_ops = {
  72     .read = microbit_i2c_read,
  73     .write = microbit_i2c_write,
  74     .endianness = DEVICE_LITTLE_ENDIAN,
  75     .impl.min_access_size = 4,
  76     .impl.max_access_size = 4,
  77 };
  78
  79 static const VMStateDescription microbit_i2c_vmstate = {
  80     .name = TYPE_MICROBIT_I2C,
  81     .version_id = 1,
  82     .minimum_version_id = 1,
  83     .fields = (VMStateField[]) {
  84         VMSTATE_UINT32_ARRAY(regs, MicrobitI2CState, MICROBIT_I2C_NREGS),
  85         VMSTATE_UINT32(read_idx, MicrobitI2CState),
  86     },
  87 };
  88
  89 static void microbit_i2c_reset(DeviceState *dev)
  90 {
  91     MicrobitI2CState *s = MICROBIT_I2C(dev);
  92
  93     memset(s->regs, 0, sizeof(s->regs));
  94     s->read_idx = 0;
  95 }
  96
  97 static void microbit_i2c_realize(DeviceState *dev, Error **errp)
  98 {
  99     SysBusDevice *sbd = SYS_BUS_DEVICE(dev);
 100     MicrobitI2CState *s = MICROBIT_I2C(dev);
 101
 102     memory_region_init_io(&s->iomem, OBJECT(s), &microbit_i2c_ops, s,
 103                           "microbit.twi", NRF51_PERIPHERAL_SIZE);
 104     sysbus_init_mmio(sbd, &s->iomem);
 105 }
 106
 107 static void microbit_i2c_class_init(ObjectClass *klass, void *data)
 108 {
 109     DeviceClass *dc = DEVICE_CLASS(klass);
 110
 111     dc->vmsd = &microbit_i2c_vmstate;
 112     dc->reset = microbit_i2c_reset;
 113     dc->realize = microbit_i2c_realize;
 114     dc->desc = "Microbit I2C controller";
 115 }
 116
 117 static const TypeInfo microbit_i2c_info = {
 118     .name = TYPE_MICROBIT_I2C,
 119     .parent = TYPE_SYS_BUS_DEVICE,
 120     .instance_size = sizeof(MicrobitI2CState),
 121     .class_init = microbit_i2c_class_init,
 122 };
 123
 124 static void microbit_i2c_register_types(void)
 125 {
 126     type_register_static(&microbit_i2c_info);
 127 }
 128
 129 type_init(microbit_i2c_register_types)