1 /* 2 * ARM CMSDK APB UART emulation 3 * 4 * Copyright (c) 2017 Linaro Limited 5 * Written by Peter Maydell 6 * 7 * This program is free software; you can redistribute it and/or modify 8 * it under the terms of the GNU General Public License version 2 or 9 * (at your option) any later version. 10 */ 11 12 /* This is a model of the "APB UART" which is part of the Cortex-M 13 * System Design Kit (CMSDK) and documented in the Cortex-M System 14 * Design Kit Technical Reference Manual (ARM DDI0479C): 15 * https://developer.arm.com/products/system-design/system-design-kits/cortex-m-system-design-kit 16 */ 17 18 #include "qemu/osdep.h" 19 #include "qemu/log.h" 20 #include "qemu/module.h" 21 #include "qapi/error.h" 22 #include "trace.h" 23 #include "hw/sysbus.h" 24 #include "migration/vmstate.h" 25 #include "hw/registerfields.h" 26 #include "chardev/char-fe.h" 27 #include "chardev/char-serial.h" 28 #include "hw/char/cmsdk-apb-uart.h" 29 #include "hw/irq.h" 30 #include "hw/qdev-properties-system.h" 31 32 REG32(DATA, 0) 33 REG32(STATE, 4) 34 FIELD(STATE, TXFULL, 0, 1) 35 FIELD(STATE, RXFULL, 1, 1) 36 FIELD(STATE, TXOVERRUN, 2, 1) 37 FIELD(STATE, RXOVERRUN, 3, 1) 38 REG32(CTRL, 8) 39 FIELD(CTRL, TX_EN, 0, 1) 40 FIELD(CTRL, RX_EN, 1, 1) 41 FIELD(CTRL, TX_INTEN, 2, 1) 42 FIELD(CTRL, RX_INTEN, 3, 1) 43 FIELD(CTRL, TXO_INTEN, 4, 1) 44 FIELD(CTRL, RXO_INTEN, 5, 1) 45 FIELD(CTRL, HSTEST, 6, 1) 46 REG32(INTSTATUS, 0xc) 47 FIELD(INTSTATUS, TX, 0, 1) 48 FIELD(INTSTATUS, RX, 1, 1) 49 FIELD(INTSTATUS, TXO, 2, 1) 50 FIELD(INTSTATUS, RXO, 3, 1) 51 REG32(BAUDDIV, 0x10) 52 REG32(PID4, 0xFD0) 53 REG32(PID5, 0xFD4) 54 REG32(PID6, 0xFD8) 55 REG32(PID7, 0xFDC) 56 REG32(PID0, 0xFE0) 57 REG32(PID1, 0xFE4) 58 REG32(PID2, 0xFE8) 59 REG32(PID3, 0xFEC) 60 REG32(CID0, 0xFF0) 61 REG32(CID1, 0xFF4) 62 REG32(CID2, 0xFF8) 63 REG32(CID3, 0xFFC) 64 65 /* PID/CID values */ 66 static const int uart_id[] = { 67 0x04, 0x00, 0x00, 0x00, /* PID4..PID7 */ 68 0x21, 0xb8, 0x1b, 0x00, /* PID0..PID3 */ 69 0x0d, 0xf0, 0x05, 0xb1, /* CID0..CID3 */ 70 }; 71 72 static bool uart_baudrate_ok(CMSDKAPBUART *s) 73 { 74 /* The minimum permitted bauddiv setting is 16, so we just ignore 75 * settings below that (usually this means the device has just 76 * been reset and not yet programmed). 77 */ 78 return s->bauddiv >= 16 && s->bauddiv <= s->pclk_frq; 79 } 80 81 static void uart_update_parameters(CMSDKAPBUART *s) 82 { 83 QEMUSerialSetParams ssp; 84 85 /* This UART is always 8N1 but the baud rate is programmable. */ 86 if (!uart_baudrate_ok(s)) { 87 return; 88 } 89 90 ssp.data_bits = 8; 91 ssp.parity = 'N'; 92 ssp.stop_bits = 1; 93 ssp.speed = s->pclk_frq / s->bauddiv; 94 qemu_chr_fe_ioctl(&s->chr, CHR_IOCTL_SERIAL_SET_PARAMS, &ssp); 95 trace_cmsdk_apb_uart_set_params(ssp.speed); 96 } 97 98 static void cmsdk_apb_uart_update(CMSDKAPBUART *s) 99 { 100 /* update outbound irqs, including handling the way the rxo and txo 101 * interrupt status bits are just logical AND of the overrun bit in 102 * STATE and the overrun interrupt enable bit in CTRL. 103 */ 104 uint32_t omask = (R_INTSTATUS_RXO_MASK | R_INTSTATUS_TXO_MASK); 105 s->intstatus &= ~omask; 106 s->intstatus |= (s->state & (s->ctrl >> 2) & omask); 107 108 qemu_set_irq(s->txint, !!(s->intstatus & R_INTSTATUS_TX_MASK)); 109 qemu_set_irq(s->rxint, !!(s->intstatus & R_INTSTATUS_RX_MASK)); 110 qemu_set_irq(s->txovrint, !!(s->intstatus & R_INTSTATUS_TXO_MASK)); 111 qemu_set_irq(s->rxovrint, !!(s->intstatus & R_INTSTATUS_RXO_MASK)); 112 qemu_set_irq(s->uartint, !!(s->intstatus)); 113 } 114 115 static int uart_can_receive(void *opaque) 116 { 117 CMSDKAPBUART *s = CMSDK_APB_UART(opaque); 118 119 /* We can take a char if RX is enabled and the buffer is empty */ 120 if (s->ctrl & R_CTRL_RX_EN_MASK && !(s->state & R_STATE_RXFULL_MASK)) { 121 return 1; 122 } 123 return 0; 124 } 125 126 static void uart_receive(void *opaque, const uint8_t *buf, int size) 127 { 128 CMSDKAPBUART *s = CMSDK_APB_UART(opaque); 129 130 trace_cmsdk_apb_uart_receive(*buf); 131 132 /* In fact uart_can_receive() ensures that we can't be 133 * called unless RX is enabled and the buffer is empty, 134 * but we include this logic as documentation of what the 135 * hardware does if a character arrives in these circumstances. 136 */ 137 if (!(s->ctrl & R_CTRL_RX_EN_MASK)) { 138 /* Just drop the character on the floor */ 139 return; 140 } 141 142 if (s->state & R_STATE_RXFULL_MASK) { 143 s->state |= R_STATE_RXOVERRUN_MASK; 144 } 145 146 s->rxbuf = *buf; 147 s->state |= R_STATE_RXFULL_MASK; 148 if (s->ctrl & R_CTRL_RX_INTEN_MASK) { 149 s->intstatus |= R_INTSTATUS_RX_MASK; 150 } 151 cmsdk_apb_uart_update(s); 152 } 153 154 static uint64_t uart_read(void *opaque, hwaddr offset, unsigned size) 155 { 156 CMSDKAPBUART *s = CMSDK_APB_UART(opaque); 157 uint64_t r; 158 159 switch (offset) { 160 case A_DATA: 161 r = s->rxbuf; 162 s->state &= ~R_STATE_RXFULL_MASK; 163 cmsdk_apb_uart_update(s); 164 qemu_chr_fe_accept_input(&s->chr); 165 break; 166 case A_STATE: 167 r = s->state; 168 break; 169 case A_CTRL: 170 r = s->ctrl; 171 break; 172 case A_INTSTATUS: 173 r = s->intstatus; 174 break; 175 case A_BAUDDIV: 176 r = s->bauddiv; 177 break; 178 case A_PID4 ... A_CID3: 179 r = uart_id[(offset - A_PID4) / 4]; 180 break; 181 default: 182 qemu_log_mask(LOG_GUEST_ERROR, 183 "CMSDK APB UART read: bad offset %x\n", (int) offset); 184 r = 0; 185 break; 186 } 187 trace_cmsdk_apb_uart_read(offset, r, size); 188 return r; 189 } 190 191 /* Try to send tx data, and arrange to be called back later if 192 * we can't (ie the char backend is busy/blocking). 193 */ 194 static gboolean uart_transmit(void *do_not_use, GIOCondition cond, void *opaque) 195 { 196 CMSDKAPBUART *s = CMSDK_APB_UART(opaque); 197 int ret; 198 199 s->watch_tag = 0; 200 201 if (!(s->ctrl & R_CTRL_TX_EN_MASK) || !(s->state & R_STATE_TXFULL_MASK)) { 202 return G_SOURCE_REMOVE; 203 } 204 205 ret = qemu_chr_fe_write(&s->chr, &s->txbuf, 1); 206 if (ret <= 0) { 207 s->watch_tag = qemu_chr_fe_add_watch(&s->chr, G_IO_OUT | G_IO_HUP, 208 uart_transmit, s); 209 if (!s->watch_tag) { 210 /* Most common reason to be here is "no chardev backend": 211 * just insta-drain the buffer, so the serial output 212 * goes into a void, rather than blocking the guest. 213 */ 214 goto buffer_drained; 215 } 216 /* Transmit pending */ 217 trace_cmsdk_apb_uart_tx_pending(); 218 return G_SOURCE_REMOVE; 219 } 220 221 buffer_drained: 222 /* Character successfully sent */ 223 trace_cmsdk_apb_uart_tx(s->txbuf); 224 s->state &= ~R_STATE_TXFULL_MASK; 225 /* Going from TXFULL set to clear triggers the tx interrupt */ 226 if (s->ctrl & R_CTRL_TX_INTEN_MASK) { 227 s->intstatus |= R_INTSTATUS_TX_MASK; 228 } 229 cmsdk_apb_uart_update(s); 230 return G_SOURCE_REMOVE; 231 } 232 233 static void uart_cancel_transmit(CMSDKAPBUART *s) 234 { 235 if (s->watch_tag) { 236 g_source_remove(s->watch_tag); 237 s->watch_tag = 0; 238 } 239 } 240 241 static void uart_write(void *opaque, hwaddr offset, uint64_t value, 242 unsigned size) 243 { 244 CMSDKAPBUART *s = CMSDK_APB_UART(opaque); 245 246 trace_cmsdk_apb_uart_write(offset, value, size); 247 248 switch (offset) { 249 case A_DATA: 250 s->txbuf = value; 251 if (s->state & R_STATE_TXFULL_MASK) { 252 /* Buffer already full -- note the overrun and let the 253 * existing pending transmit callback handle the new char. 254 */ 255 s->state |= R_STATE_TXOVERRUN_MASK; 256 cmsdk_apb_uart_update(s); 257 } else { 258 s->state |= R_STATE_TXFULL_MASK; 259 uart_transmit(NULL, G_IO_OUT, s); 260 } 261 break; 262 case A_STATE: 263 /* Bits 0 and 1 are read only; bits 2 and 3 are W1C */ 264 s->state &= ~(value & 265 (R_STATE_TXOVERRUN_MASK | R_STATE_RXOVERRUN_MASK)); 266 cmsdk_apb_uart_update(s); 267 break; 268 case A_CTRL: 269 s->ctrl = value & 0x7f; 270 if ((s->ctrl & R_CTRL_TX_EN_MASK) && !uart_baudrate_ok(s)) { 271 qemu_log_mask(LOG_GUEST_ERROR, 272 "CMSDK APB UART: Tx enabled with invalid baudrate\n"); 273 } 274 cmsdk_apb_uart_update(s); 275 break; 276 case A_INTSTATUS: 277 /* All bits are W1C. Clearing the overrun interrupt bits really 278 * clears the overrun status bits in the STATE register (which 279 * is then reflected into the intstatus value by the update function). 280 */ 281 s->state &= ~(value & (R_INTSTATUS_TXO_MASK | R_INTSTATUS_RXO_MASK)); 282 s->intstatus &= ~value; 283 cmsdk_apb_uart_update(s); 284 break; 285 case A_BAUDDIV: 286 s->bauddiv = value & 0xFFFFF; 287 uart_update_parameters(s); 288 break; 289 case A_PID4 ... A_CID3: 290 qemu_log_mask(LOG_GUEST_ERROR, 291 "CMSDK APB UART write: write to RO offset 0x%x\n", 292 (int)offset); 293 break; 294 default: 295 qemu_log_mask(LOG_GUEST_ERROR, 296 "CMSDK APB UART write: bad offset 0x%x\n", (int) offset); 297 break; 298 } 299 } 300 301 static const MemoryRegionOps uart_ops = { 302 .read = uart_read, 303 .write = uart_write, 304 .endianness = DEVICE_LITTLE_ENDIAN, 305 }; 306 307 static void cmsdk_apb_uart_reset(DeviceState *dev) 308 { 309 CMSDKAPBUART *s = CMSDK_APB_UART(dev); 310 311 trace_cmsdk_apb_uart_reset(); 312 uart_cancel_transmit(s); 313 s->state = 0; 314 s->ctrl = 0; 315 s->intstatus = 0; 316 s->bauddiv = 0; 317 s->txbuf = 0; 318 s->rxbuf = 0; 319 } 320 321 static void cmsdk_apb_uart_init(Object *obj) 322 { 323 SysBusDevice *sbd = SYS_BUS_DEVICE(obj); 324 CMSDKAPBUART *s = CMSDK_APB_UART(obj); 325 326 memory_region_init_io(&s->iomem, obj, &uart_ops, s, "uart", 0x1000); 327 sysbus_init_mmio(sbd, &s->iomem); 328 sysbus_init_irq(sbd, &s->txint); 329 sysbus_init_irq(sbd, &s->rxint); 330 sysbus_init_irq(sbd, &s->txovrint); 331 sysbus_init_irq(sbd, &s->rxovrint); 332 sysbus_init_irq(sbd, &s->uartint); 333 } 334 335 static void cmsdk_apb_uart_realize(DeviceState *dev, Error **errp) 336 { 337 CMSDKAPBUART *s = CMSDK_APB_UART(dev); 338 339 if (s->pclk_frq == 0) { 340 error_setg(errp, "CMSDK APB UART: pclk-frq property must be set"); 341 return; 342 } 343 344 /* This UART has no flow control, so we do not need to register 345 * an event handler to deal with CHR_EVENT_BREAK. 346 */ 347 qemu_chr_fe_set_handlers(&s->chr, uart_can_receive, uart_receive, 348 NULL, NULL, s, NULL, true); 349 } 350 351 static int cmsdk_apb_uart_post_load(void *opaque, int version_id) 352 { 353 CMSDKAPBUART *s = CMSDK_APB_UART(opaque); 354 355 /* If we have a pending character, arrange to resend it. */ 356 if (s->state & R_STATE_TXFULL_MASK) { 357 s->watch_tag = qemu_chr_fe_add_watch(&s->chr, G_IO_OUT | G_IO_HUP, 358 uart_transmit, s); 359 } 360 uart_update_parameters(s); 361 return 0; 362 } 363 364 static const VMStateDescription cmsdk_apb_uart_vmstate = { 365 .name = "cmsdk-apb-uart", 366 .version_id = 1, 367 .minimum_version_id = 1, 368 .post_load = cmsdk_apb_uart_post_load, 369 .fields = (const VMStateField[]) { 370 VMSTATE_UINT32(state, CMSDKAPBUART), 371 VMSTATE_UINT32(ctrl, CMSDKAPBUART), 372 VMSTATE_UINT32(intstatus, CMSDKAPBUART), 373 VMSTATE_UINT32(bauddiv, CMSDKAPBUART), 374 VMSTATE_UINT8(txbuf, CMSDKAPBUART), 375 VMSTATE_UINT8(rxbuf, CMSDKAPBUART), 376 VMSTATE_END_OF_LIST() 377 } 378 }; 379 380 static Property cmsdk_apb_uart_properties[] = { 381 DEFINE_PROP_CHR("chardev", CMSDKAPBUART, chr), 382 DEFINE_PROP_UINT32("pclk-frq", CMSDKAPBUART, pclk_frq, 0), 383 DEFINE_PROP_END_OF_LIST(), 384 }; 385 386 static void cmsdk_apb_uart_class_init(ObjectClass *klass, void *data) 387 { 388 DeviceClass *dc = DEVICE_CLASS(klass); 389 390 dc->realize = cmsdk_apb_uart_realize; 391 dc->vmsd = &cmsdk_apb_uart_vmstate; 392 dc->reset = cmsdk_apb_uart_reset; 393 device_class_set_props(dc, cmsdk_apb_uart_properties); 394 } 395 396 static const TypeInfo cmsdk_apb_uart_info = { 397 .name = TYPE_CMSDK_APB_UART, 398 .parent = TYPE_SYS_BUS_DEVICE, 399 .instance_size = sizeof(CMSDKAPBUART), 400 .instance_init = cmsdk_apb_uart_init, 401 .class_init = cmsdk_apb_uart_class_init, 402 }; 403 404 static void cmsdk_apb_uart_register_types(void) 405 { 406 type_register_static(&cmsdk_apb_uart_info); 407 } 408 409 type_init(cmsdk_apb_uart_register_types); 410