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 = (const VMStateField[]) { 84 VMSTATE_UINT32_ARRAY(regs, MicrobitI2CState, MICROBIT_I2C_NREGS), 85 VMSTATE_UINT32(read_idx, MicrobitI2CState), 86 VMSTATE_END_OF_LIST() 87 }, 88 }; 89 90 static void microbit_i2c_reset(DeviceState *dev) 91 { 92 MicrobitI2CState *s = MICROBIT_I2C(dev); 93 94 memset(s->regs, 0, sizeof(s->regs)); 95 s->read_idx = 0; 96 } 97 98 static void microbit_i2c_realize(DeviceState *dev, Error **errp) 99 { 100 SysBusDevice *sbd = SYS_BUS_DEVICE(dev); 101 MicrobitI2CState *s = MICROBIT_I2C(dev); 102 103 memory_region_init_io(&s->iomem, OBJECT(s), µbit_i2c_ops, s, 104 "microbit.twi", NRF51_PERIPHERAL_SIZE); 105 sysbus_init_mmio(sbd, &s->iomem); 106 } 107 108 static void microbit_i2c_class_init(ObjectClass *klass, void *data) 109 { 110 DeviceClass *dc = DEVICE_CLASS(klass); 111 112 dc->vmsd = µbit_i2c_vmstate; 113 dc->reset = microbit_i2c_reset; 114 dc->realize = microbit_i2c_realize; 115 dc->desc = "Microbit I2C controller"; 116 } 117 118 static const TypeInfo microbit_i2c_info = { 119 .name = TYPE_MICROBIT_I2C, 120 .parent = TYPE_SYS_BUS_DEVICE, 121 .instance_size = sizeof(MicrobitI2CState), 122 .class_init = microbit_i2c_class_init, 123 }; 124 125 static void microbit_i2c_register_types(void) 126 { 127 type_register_static(µbit_i2c_info); 128 } 129 130 type_init(microbit_i2c_register_types) 131