1 /* 2 * AVR USART 3 * 4 * Copyright (c) 2018 University of Kent 5 * Author: Sarah Harris 6 * 7 * This library is free software; you can redistribute it and/or 8 * modify it under the terms of the GNU Lesser General Public 9 * License as published by the Free Software Foundation; either 10 * version 2.1 of the License, or (at your option) any later version. 11 * 12 * This library is distributed in the hope that it will be useful, 13 * but WITHOUT ANY WARRANTY; without even the implied warranty of 14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 15 * Lesser General Public License for more details. 16 * 17 * You should have received a copy of the GNU Lesser General Public 18 * License along with this library; if not, see 19 * <http://www.gnu.org/licenses/lgpl-2.1.html> 20 */ 21 22 #include "qemu/osdep.h" 23 #include "hw/char/avr_usart.h" 24 #include "qemu/log.h" 25 #include "hw/irq.h" 26 #include "hw/qdev-properties.h" 27 #include "hw/qdev-properties-system.h" 28 29 static int avr_usart_can_receive(void *opaque) 30 { 31 AVRUsartState *usart = opaque; 32 33 if (usart->data_valid || !(usart->csrb & USART_CSRB_RXEN)) { 34 return 0; 35 } 36 return 1; 37 } 38 39 static void avr_usart_receive(void *opaque, const uint8_t *buffer, int size) 40 { 41 AVRUsartState *usart = opaque; 42 assert(size == 1); 43 assert(!usart->data_valid); 44 usart->data = buffer[0]; 45 usart->data_valid = true; 46 usart->csra |= USART_CSRA_RXC; 47 if (usart->csrb & USART_CSRB_RXCIE) { 48 qemu_set_irq(usart->rxc_irq, 1); 49 } 50 } 51 52 static void update_char_mask(AVRUsartState *usart) 53 { 54 uint8_t mode = ((usart->csrc & USART_CSRC_CSZ0) ? 1 : 0) | 55 ((usart->csrc & USART_CSRC_CSZ1) ? 2 : 0) | 56 ((usart->csrb & USART_CSRB_CSZ2) ? 4 : 0); 57 switch (mode) { 58 case 0: 59 usart->char_mask = 0b11111; 60 break; 61 case 1: 62 usart->char_mask = 0b111111; 63 break; 64 case 2: 65 usart->char_mask = 0b1111111; 66 break; 67 case 3: 68 usart->char_mask = 0b11111111; 69 break; 70 case 4: 71 /* Fallthrough. */ 72 case 5: 73 /* Fallthrough. */ 74 case 6: 75 qemu_log_mask( 76 LOG_GUEST_ERROR, 77 "%s: Reserved character size 0x%x\n", 78 __func__, 79 mode); 80 break; 81 case 7: 82 qemu_log_mask( 83 LOG_GUEST_ERROR, 84 "%s: Nine bit character size not supported (forcing eight)\n", 85 __func__); 86 usart->char_mask = 0b11111111; 87 break; 88 default: 89 assert(0); 90 } 91 } 92 93 static void avr_usart_reset(DeviceState *dev) 94 { 95 AVRUsartState *usart = AVR_USART(dev); 96 usart->data_valid = false; 97 usart->csra = 0b00100000; 98 usart->csrb = 0b00000000; 99 usart->csrc = 0b00000110; 100 usart->brrl = 0; 101 usart->brrh = 0; 102 update_char_mask(usart); 103 qemu_set_irq(usart->rxc_irq, 0); 104 qemu_set_irq(usart->txc_irq, 0); 105 qemu_set_irq(usart->dre_irq, 0); 106 } 107 108 static uint64_t avr_usart_read(void *opaque, hwaddr addr, unsigned int size) 109 { 110 AVRUsartState *usart = opaque; 111 uint8_t data; 112 assert(size == 1); 113 114 if (!usart->enabled) { 115 return 0; 116 } 117 118 switch (addr) { 119 case USART_DR: 120 if (!(usart->csrb & USART_CSRB_RXEN)) { 121 /* Receiver disabled, ignore. */ 122 return 0; 123 } 124 if (usart->data_valid) { 125 data = usart->data & usart->char_mask; 126 usart->data_valid = false; 127 } else { 128 data = 0; 129 } 130 usart->csra &= 0xff ^ USART_CSRA_RXC; 131 qemu_set_irq(usart->rxc_irq, 0); 132 qemu_chr_fe_accept_input(&usart->chr); 133 return data; 134 case USART_CSRA: 135 return usart->csra; 136 case USART_CSRB: 137 return usart->csrb; 138 case USART_CSRC: 139 return usart->csrc; 140 case USART_BRRL: 141 return usart->brrl; 142 case USART_BRRH: 143 return usart->brrh; 144 default: 145 qemu_log_mask( 146 LOG_GUEST_ERROR, 147 "%s: Bad offset 0x%"HWADDR_PRIx"\n", 148 __func__, 149 addr); 150 } 151 return 0; 152 } 153 154 static void avr_usart_write(void *opaque, hwaddr addr, uint64_t value, 155 unsigned int size) 156 { 157 AVRUsartState *usart = opaque; 158 uint8_t mask; 159 uint8_t data; 160 assert((value & 0xff) == value); 161 assert(size == 1); 162 163 if (!usart->enabled) { 164 return; 165 } 166 167 switch (addr) { 168 case USART_DR: 169 if (!(usart->csrb & USART_CSRB_TXEN)) { 170 /* Transmitter disabled, ignore. */ 171 return; 172 } 173 usart->csra |= USART_CSRA_TXC; 174 usart->csra |= USART_CSRA_DRE; 175 if (usart->csrb & USART_CSRB_TXCIE) { 176 qemu_set_irq(usart->txc_irq, 1); 177 usart->csra &= 0xff ^ USART_CSRA_TXC; 178 } 179 if (usart->csrb & USART_CSRB_DREIE) { 180 qemu_set_irq(usart->dre_irq, 1); 181 } 182 data = value; 183 qemu_chr_fe_write_all(&usart->chr, &data, 1); 184 break; 185 case USART_CSRA: 186 mask = 0b01000011; 187 /* Mask read-only bits. */ 188 value = (value & mask) | (usart->csra & (0xff ^ mask)); 189 usart->csra = value; 190 if (value & USART_CSRA_TXC) { 191 usart->csra ^= USART_CSRA_TXC; 192 qemu_set_irq(usart->txc_irq, 0); 193 } 194 if (value & USART_CSRA_MPCM) { 195 qemu_log_mask( 196 LOG_GUEST_ERROR, 197 "%s: MPCM not supported by USART\n", 198 __func__); 199 } 200 break; 201 case USART_CSRB: 202 mask = 0b11111101; 203 /* Mask read-only bits. */ 204 value = (value & mask) | (usart->csrb & (0xff ^ mask)); 205 usart->csrb = value; 206 if (!(value & USART_CSRB_RXEN)) { 207 /* Receiver disabled, flush input buffer. */ 208 usart->data_valid = false; 209 } 210 qemu_set_irq(usart->rxc_irq, 211 ((value & USART_CSRB_RXCIE) && 212 (usart->csra & USART_CSRA_RXC)) ? 1 : 0); 213 qemu_set_irq(usart->txc_irq, 214 ((value & USART_CSRB_TXCIE) && 215 (usart->csra & USART_CSRA_TXC)) ? 1 : 0); 216 qemu_set_irq(usart->dre_irq, 217 ((value & USART_CSRB_DREIE) && 218 (usart->csra & USART_CSRA_DRE)) ? 1 : 0); 219 update_char_mask(usart); 220 break; 221 case USART_CSRC: 222 usart->csrc = value; 223 if ((value & USART_CSRC_MSEL1) && (value & USART_CSRC_MSEL0)) { 224 qemu_log_mask( 225 LOG_GUEST_ERROR, 226 "%s: SPI mode not supported by USART\n", 227 __func__); 228 } 229 if ((value & USART_CSRC_MSEL1) && !(value & USART_CSRC_MSEL0)) { 230 qemu_log_mask(LOG_GUEST_ERROR, "%s: Bad USART mode\n", __func__); 231 } 232 if (!(value & USART_CSRC_PM1) && (value & USART_CSRC_PM0)) { 233 qemu_log_mask( 234 LOG_GUEST_ERROR, 235 "%s: Bad USART parity mode\n", 236 __func__); 237 } 238 update_char_mask(usart); 239 break; 240 case USART_BRRL: 241 usart->brrl = value; 242 break; 243 case USART_BRRH: 244 usart->brrh = value & 0b00001111; 245 break; 246 default: 247 qemu_log_mask( 248 LOG_GUEST_ERROR, 249 "%s: Bad offset 0x%"HWADDR_PRIx"\n", 250 __func__, 251 addr); 252 } 253 } 254 255 static const MemoryRegionOps avr_usart_ops = { 256 .read = avr_usart_read, 257 .write = avr_usart_write, 258 .endianness = DEVICE_NATIVE_ENDIAN, 259 .impl = {.min_access_size = 1, .max_access_size = 1} 260 }; 261 262 static Property avr_usart_properties[] = { 263 DEFINE_PROP_CHR("chardev", AVRUsartState, chr), 264 DEFINE_PROP_END_OF_LIST(), 265 }; 266 267 static void avr_usart_pr(void *opaque, int irq, int level) 268 { 269 AVRUsartState *s = AVR_USART(opaque); 270 271 s->enabled = !level; 272 273 if (!s->enabled) { 274 avr_usart_reset(DEVICE(s)); 275 } 276 } 277 278 static void avr_usart_init(Object *obj) 279 { 280 AVRUsartState *s = AVR_USART(obj); 281 sysbus_init_irq(SYS_BUS_DEVICE(obj), &s->rxc_irq); 282 sysbus_init_irq(SYS_BUS_DEVICE(obj), &s->dre_irq); 283 sysbus_init_irq(SYS_BUS_DEVICE(obj), &s->txc_irq); 284 memory_region_init_io(&s->mmio, obj, &avr_usart_ops, s, TYPE_AVR_USART, 7); 285 sysbus_init_mmio(SYS_BUS_DEVICE(obj), &s->mmio); 286 qdev_init_gpio_in(DEVICE(s), avr_usart_pr, 1); 287 s->enabled = true; 288 } 289 290 static void avr_usart_realize(DeviceState *dev, Error **errp) 291 { 292 AVRUsartState *s = AVR_USART(dev); 293 qemu_chr_fe_set_handlers(&s->chr, avr_usart_can_receive, 294 avr_usart_receive, NULL, NULL, 295 s, NULL, true); 296 avr_usart_reset(dev); 297 } 298 299 static void avr_usart_class_init(ObjectClass *klass, void *data) 300 { 301 DeviceClass *dc = DEVICE_CLASS(klass); 302 303 device_class_set_legacy_reset(dc, avr_usart_reset); 304 device_class_set_props(dc, avr_usart_properties); 305 dc->realize = avr_usart_realize; 306 } 307 308 static const TypeInfo avr_usart_info = { 309 .name = TYPE_AVR_USART, 310 .parent = TYPE_SYS_BUS_DEVICE, 311 .instance_size = sizeof(AVRUsartState), 312 .instance_init = avr_usart_init, 313 .class_init = avr_usart_class_init, 314 }; 315 316 static void avr_usart_register_types(void) 317 { 318 type_register_static(&avr_usart_info); 319 } 320 321 type_init(avr_usart_register_types) 322