1 /*
2 * QEMU GRLIB APB UART Emulator
3 *
4 * SPDX-License-Identifier: MIT
5 *
6 * Copyright (c) 2010-2024 AdaCore
7 *
8 * Permission is hereby granted, free of charge, to any person obtaining a copy
9 * of this software and associated documentation files (the "Software"), to deal
10 * in the Software without restriction, including without limitation the rights
11 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
12 * copies of the Software, and to permit persons to whom the Software is
13 * furnished to do so, subject to the following conditions:
14 *
15 * The above copyright notice and this permission notice shall be included in
16 * all copies or substantial portions of the Software.
17 *
18 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
19 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
20 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
21 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
22 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
23 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
24 * THE SOFTWARE.
25 */
26
27 #include "qemu/osdep.h"
28 #include "hw/irq.h"
29 #include "hw/qdev-properties.h"
30 #include "hw/qdev-properties-system.h"
31 #include "hw/char/grlib_uart.h"
32 #include "hw/sysbus.h"
33 #include "qemu/module.h"
34 #include "chardev/char-fe.h"
35
36 #include "trace.h"
37 #include "qom/object.h"
38
39 #define UART_REG_SIZE 20 /* Size of memory mapped registers */
40
41 /* UART status register fields */
42 #define UART_DATA_READY (1 << 0)
43 #define UART_TRANSMIT_SHIFT_EMPTY (1 << 1)
44 #define UART_TRANSMIT_FIFO_EMPTY (1 << 2)
45 #define UART_BREAK_RECEIVED (1 << 3)
46 #define UART_OVERRUN (1 << 4)
47 #define UART_PARITY_ERROR (1 << 5)
48 #define UART_FRAMING_ERROR (1 << 6)
49 #define UART_TRANSMIT_FIFO_HALF (1 << 7)
50 #define UART_RECEIVE_FIFO_HALF (1 << 8)
51 #define UART_TRANSMIT_FIFO_FULL (1 << 9)
52 #define UART_RECEIVE_FIFO_FULL (1 << 10)
53
54 /* UART control register fields */
55 #define UART_RECEIVE_ENABLE (1 << 0)
56 #define UART_TRANSMIT_ENABLE (1 << 1)
57 #define UART_RECEIVE_INTERRUPT (1 << 2)
58 #define UART_TRANSMIT_INTERRUPT (1 << 3)
59 #define UART_PARITY_SELECT (1 << 4)
60 #define UART_PARITY_ENABLE (1 << 5)
61 #define UART_FLOW_CONTROL (1 << 6)
62 #define UART_LOOPBACK (1 << 7)
63 #define UART_EXTERNAL_CLOCK (1 << 8)
64 #define UART_RECEIVE_FIFO_INTERRUPT (1 << 9)
65 #define UART_TRANSMIT_FIFO_INTERRUPT (1 << 10)
66 #define UART_FIFO_DEBUG_MODE (1 << 11)
67 #define UART_OUTPUT_ENABLE (1 << 12)
68 #define UART_FIFO_AVAILABLE (1 << 31)
69
70 /* Memory mapped register offsets */
71 #define DATA_OFFSET 0x00
72 #define STATUS_OFFSET 0x04
73 #define CONTROL_OFFSET 0x08
74 #define SCALER_OFFSET 0x0C /* not supported */
75 #define FIFO_DEBUG_OFFSET 0x10 /* not supported */
76
77 #define FIFO_LENGTH 1024
78
79 OBJECT_DECLARE_SIMPLE_TYPE(UART, GRLIB_APB_UART)
80
81 struct UART {
82 SysBusDevice parent_obj;
83
84 MemoryRegion iomem;
85 qemu_irq irq;
86
87 CharBackend chr;
88
89 /* registers */
90 uint32_t status;
91 uint32_t control;
92
93 /* FIFO */
94 char buffer[FIFO_LENGTH];
95 int len;
96 int current;
97 };
98
uart_data_to_read(UART * uart)99 static int uart_data_to_read(UART *uart)
100 {
101 return uart->current < uart->len;
102 }
103
uart_pop(UART * uart)104 static char uart_pop(UART *uart)
105 {
106 char ret;
107
108 if (uart->len == 0) {
109 uart->status &= ~UART_DATA_READY;
110 return 0;
111 }
112
113 ret = uart->buffer[uart->current++];
114
115 if (uart->current >= uart->len) {
116 /* Flush */
117 uart->len = 0;
118 uart->current = 0;
119 }
120
121 if (!uart_data_to_read(uart)) {
122 uart->status &= ~UART_DATA_READY;
123 }
124
125 return ret;
126 }
127
uart_add_to_fifo(UART * uart,const uint8_t * buffer,int length)128 static void uart_add_to_fifo(UART *uart,
129 const uint8_t *buffer,
130 int length)
131 {
132 if (uart->len + length > FIFO_LENGTH) {
133 abort();
134 }
135 memcpy(uart->buffer + uart->len, buffer, length);
136 uart->len += length;
137 }
138
grlib_apbuart_can_receive(void * opaque)139 static int grlib_apbuart_can_receive(void *opaque)
140 {
141 UART *uart = opaque;
142
143 return FIFO_LENGTH - uart->len;
144 }
145
grlib_apbuart_receive(void * opaque,const uint8_t * buf,int size)146 static void grlib_apbuart_receive(void *opaque, const uint8_t *buf, int size)
147 {
148 UART *uart = opaque;
149
150 if (uart->control & UART_RECEIVE_ENABLE) {
151 uart_add_to_fifo(uart, buf, size);
152
153 uart->status |= UART_DATA_READY;
154
155 if (uart->control & UART_RECEIVE_INTERRUPT) {
156 qemu_irq_pulse(uart->irq);
157 }
158 }
159 }
160
grlib_apbuart_event(void * opaque,QEMUChrEvent event)161 static void grlib_apbuart_event(void *opaque, QEMUChrEvent event)
162 {
163 trace_grlib_apbuart_event(event);
164 }
165
166
grlib_apbuart_read(void * opaque,hwaddr addr,unsigned size)167 static uint64_t grlib_apbuart_read(void *opaque, hwaddr addr,
168 unsigned size)
169 {
170 UART *uart = opaque;
171
172 addr &= 0xff;
173
174 /* Unit registers */
175 switch (addr) {
176 case DATA_OFFSET:
177 case DATA_OFFSET + 3: /* when only one byte read */
178 return uart_pop(uart);
179
180 case STATUS_OFFSET:
181 /* Read Only */
182 return uart->status;
183
184 case CONTROL_OFFSET:
185 return uart->control;
186
187 case SCALER_OFFSET:
188 /* Not supported */
189 return 0;
190
191 default:
192 trace_grlib_apbuart_readl_unknown(addr);
193 return 0;
194 }
195 }
196
grlib_apbuart_write(void * opaque,hwaddr addr,uint64_t value,unsigned size)197 static void grlib_apbuart_write(void *opaque, hwaddr addr,
198 uint64_t value, unsigned size)
199 {
200 UART *uart = opaque;
201 unsigned char c = 0;
202
203 addr &= 0xff;
204
205 /* Unit registers */
206 switch (addr) {
207 case DATA_OFFSET:
208 case DATA_OFFSET + 3: /* When only one byte write */
209 /* Transmit when character device available and transmitter enabled */
210 if (qemu_chr_fe_backend_connected(&uart->chr) &&
211 (uart->control & UART_TRANSMIT_ENABLE)) {
212 c = value & 0xFF;
213 /* XXX this blocks entire thread. Rewrite to use
214 * qemu_chr_fe_write and background I/O callbacks */
215 qemu_chr_fe_write_all(&uart->chr, &c, 1);
216 /* Generate interrupt */
217 if (uart->control & UART_TRANSMIT_INTERRUPT) {
218 qemu_irq_pulse(uart->irq);
219 }
220 }
221 return;
222
223 case STATUS_OFFSET:
224 /* Read Only */
225 return;
226
227 case CONTROL_OFFSET:
228 uart->control = value;
229 return;
230
231 case SCALER_OFFSET:
232 /* Not supported */
233 return;
234
235 default:
236 break;
237 }
238
239 trace_grlib_apbuart_writel_unknown(addr, value);
240 }
241
242 static const MemoryRegionOps grlib_apbuart_ops = {
243 .write = grlib_apbuart_write,
244 .read = grlib_apbuart_read,
245 .endianness = DEVICE_NATIVE_ENDIAN,
246 };
247
grlib_apbuart_realize(DeviceState * dev,Error ** errp)248 static void grlib_apbuart_realize(DeviceState *dev, Error **errp)
249 {
250 UART *uart = GRLIB_APB_UART(dev);
251 SysBusDevice *sbd = SYS_BUS_DEVICE(dev);
252
253 qemu_chr_fe_set_handlers(&uart->chr,
254 grlib_apbuart_can_receive,
255 grlib_apbuart_receive,
256 grlib_apbuart_event,
257 NULL, uart, NULL, true);
258
259 sysbus_init_irq(sbd, &uart->irq);
260
261 memory_region_init_io(&uart->iomem, OBJECT(uart), &grlib_apbuart_ops, uart,
262 "uart", UART_REG_SIZE);
263
264 sysbus_init_mmio(sbd, &uart->iomem);
265 }
266
grlib_apbuart_reset(DeviceState * d)267 static void grlib_apbuart_reset(DeviceState *d)
268 {
269 UART *uart = GRLIB_APB_UART(d);
270
271 /* Transmitter FIFO and shift registers are always empty in QEMU */
272 uart->status = UART_TRANSMIT_FIFO_EMPTY | UART_TRANSMIT_SHIFT_EMPTY;
273 /* Everything is off */
274 uart->control = 0;
275 /* Flush receive FIFO */
276 uart->len = 0;
277 uart->current = 0;
278 }
279
280 static Property grlib_apbuart_properties[] = {
281 DEFINE_PROP_CHR("chrdev", UART, chr),
282 DEFINE_PROP_END_OF_LIST(),
283 };
284
grlib_apbuart_class_init(ObjectClass * klass,void * data)285 static void grlib_apbuart_class_init(ObjectClass *klass, void *data)
286 {
287 DeviceClass *dc = DEVICE_CLASS(klass);
288
289 dc->realize = grlib_apbuart_realize;
290 dc->reset = grlib_apbuart_reset;
291 device_class_set_props(dc, grlib_apbuart_properties);
292 }
293
294 static const TypeInfo grlib_apbuart_info = {
295 .name = TYPE_GRLIB_APB_UART,
296 .parent = TYPE_SYS_BUS_DEVICE,
297 .instance_size = sizeof(UART),
298 .class_init = grlib_apbuart_class_init,
299 };
300
grlib_apbuart_register_types(void)301 static void grlib_apbuart_register_types(void)
302 {
303 type_register_static(&grlib_apbuart_info);
304 }
305
306 type_init(grlib_apbuart_register_types)
307