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 "hw/i2c/microbit_i2c.h"
  23
  24 static const uint32_t twi_read_sequence[] = {0x5A, 0x5A, 0x40};
  25
  26 static uint64_t microbit_i2c_read(void *opaque, hwaddr addr, unsigned int size)
  27 {
  28     MicrobitI2CState *s = opaque;
  29     uint64_t data = 0x00;
  30
  31     switch (addr) {
  32     case NRF51_TWI_EVENT_STOPPED:
  33         data = 0x01;
  34         break;
  35     case NRF51_TWI_EVENT_RXDREADY:
  36         data = 0x01;
  37         break;
  38     case NRF51_TWI_EVENT_TXDSENT:
  39         data = 0x01;
  40         break;
  41     case NRF51_TWI_REG_RXD:
  42         data = twi_read_sequence[s->read_idx];
  43         if (s->read_idx < G_N_ELEMENTS(twi_read_sequence)) {
  44             s->read_idx++;
  45         }
  46         break;
  47     default:
  48         data = s->regs[addr / sizeof(s->regs[0])];
  49         break;
  50     }
  51
  52     qemu_log_mask(LOG_UNIMP, "%s: 0x%" HWADDR_PRIx " [%u] = %" PRIx32 "\n",
  53                   __func__, addr, size, (uint32_t)data);
  54
  55
  56     return data;
  57 }
  58
  59 static void microbit_i2c_write(void *opaque, hwaddr addr, uint64_t data,
  60                                unsigned int size)
  61 {
  62     MicrobitI2CState *s = opaque;
  63
  64     qemu_log_mask(LOG_UNIMP, "%s: 0x%" HWADDR_PRIx " <- 0x%" PRIx64 " [%u]\n",
  65                   __func__, addr, data, size);
  66     s->regs[addr / sizeof(s->regs[0])] = data;
  67 }
  68
  69 static const MemoryRegionOps microbit_i2c_ops = {
  70     .read = microbit_i2c_read,
  71     .write = microbit_i2c_write,
  72     .endianness = DEVICE_LITTLE_ENDIAN,
  73     .impl.min_access_size = 4,
  74     .impl.max_access_size = 4,
  75 };
  76
  77 static const VMStateDescription microbit_i2c_vmstate = {
  78     .name = TYPE_MICROBIT_I2C,
  79     .version_id = 1,
  80     .minimum_version_id = 1,
  81     .fields = (VMStateField[]) {
  82         VMSTATE_UINT32_ARRAY(regs, MicrobitI2CState, MICROBIT_I2C_NREGS),
  83         VMSTATE_UINT32(read_idx, MicrobitI2CState),
  84     },
  85 };
  86
  87 static void microbit_i2c_reset(DeviceState *dev)
  88 {
  89     MicrobitI2CState *s = MICROBIT_I2C(dev);
  90
  91     memset(s->regs, 0, sizeof(s->regs));
  92     s->read_idx = 0;
  93 }
  94
  95 static void microbit_i2c_realize(DeviceState *dev, Error **errp)
  96 {
  97     SysBusDevice *sbd = SYS_BUS_DEVICE(dev);
  98     MicrobitI2CState *s = MICROBIT_I2C(dev);
  99
 100     memory_region_init_io(&s->iomem, OBJECT(s), &microbit_i2c_ops, s,
 101                           "microbit.twi", NRF51_TWI_SIZE);
 102     sysbus_init_mmio(sbd, &s->iomem);
 103 }
 104
 105 static void microbit_i2c_class_init(ObjectClass *klass, void *data)
 106 {
 107     DeviceClass *dc = DEVICE_CLASS(klass);
 108
 109     dc->vmsd = &microbit_i2c_vmstate;
 110     dc->reset = microbit_i2c_reset;
 111     dc->realize = microbit_i2c_realize;
 112     dc->desc = "Microbit I2C controller";
 113 }
 114
 115 static const TypeInfo microbit_i2c_info = {
 116     .name = TYPE_MICROBIT_I2C,
 117     .parent = TYPE_SYS_BUS_DEVICE,
 118     .instance_size = sizeof(MicrobitI2CState),
 119     .class_init = microbit_i2c_class_init,
 120 };
 121
 122 static void microbit_i2c_register_types(void)
 123 {
 124     type_register_static(&microbit_i2c_info);
 125 }
 126
 127 type_init(microbit_i2c_register_types)