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