xref: /openbmc/qemu/hw/char/sifive_uart.c (revision 646b5378) 
1 /*
2  * QEMU model of the UART on the SiFive E300 and U500 series SOCs.
3  *
4  * Copyright (c) 2016 Stefan O'Rear
5  *
6  * This program is free software; you can redistribute it and/or modify it
7  * under the terms and conditions of the GNU General Public License,
8  * version 2 or later, as published by the Free Software Foundation.
9  *
10  * This program is distributed in the hope it will be useful, but WITHOUT
11  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
13  * more details.
14  *
15  * You should have received a copy of the GNU General Public License along with
16  * this program.  If not, see <http://www.gnu.org/licenses/>.
17  */
18 
19 #include "qemu/osdep.h"
20 #include "qapi/error.h"
21 #include "qemu/log.h"
22 #include "migration/vmstate.h"
23 #include "chardev/char.h"
24 #include "chardev/char-fe.h"
25 #include "hw/irq.h"
26 #include "hw/char/sifive_uart.h"
27 #include "hw/qdev-properties-system.h"
28 
29 #define TX_INTERRUPT_TRIGGER_DELAY_NS 100
30 
31 /*
32  * Not yet implemented:
33  *
34  * Transmit FIFO using "qemu/fifo8.h"
35  */
36 
37 /* Returns the state of the IP (interrupt pending) register */
38 static uint64_t sifive_uart_ip(SiFiveUARTState *s)
39 {
40     uint64_t ret = 0;
41 
42     uint64_t txcnt = SIFIVE_UART_GET_TXCNT(s->txctrl);
43     uint64_t rxcnt = SIFIVE_UART_GET_RXCNT(s->rxctrl);
44 
45     if (txcnt != 0) {
46         ret |= SIFIVE_UART_IP_TXWM;
47     }
48     if (s->rx_fifo_len > rxcnt) {
49         ret |= SIFIVE_UART_IP_RXWM;
50     }
51 
52     return ret;
53 }
54 
55 static void sifive_uart_update_irq(SiFiveUARTState *s)
56 {
57     int cond = 0;
58     if ((s->ie & SIFIVE_UART_IE_TXWM) ||
59         ((s->ie & SIFIVE_UART_IE_RXWM) && s->rx_fifo_len)) {
60         cond = 1;
61     }
62     if (cond) {
63         qemu_irq_raise(s->irq);
64     } else {
65         qemu_irq_lower(s->irq);
66     }
67 }
68 
69 static gboolean sifive_uart_xmit(void *do_not_use, GIOCondition cond,
70                                  void *opaque)
71 {
72     SiFiveUARTState *s = opaque;
73     int ret;
74     const uint8_t *characters;
75     uint32_t numptr = 0;
76 
77     /* instant drain the fifo when there's no back-end */
78     if (!qemu_chr_fe_backend_connected(&s->chr)) {
79         fifo8_reset(&s->tx_fifo);
80         return G_SOURCE_REMOVE;
81     }
82 
83     if (fifo8_is_empty(&s->tx_fifo)) {
84         return G_SOURCE_REMOVE;
85     }
86 
87     /* Don't pop the FIFO in case the write fails */
88     characters = fifo8_peek_bufptr(&s->tx_fifo,
89                                    fifo8_num_used(&s->tx_fifo), &numptr);
90     ret = qemu_chr_fe_write(&s->chr, characters, numptr);
91 
92     if (ret >= 0) {
93         /* We wrote the data, actually pop the fifo */
94         fifo8_pop_bufptr(&s->tx_fifo, ret, NULL);
95     }
96 
97     if (!fifo8_is_empty(&s->tx_fifo)) {
98         guint r = qemu_chr_fe_add_watch(&s->chr, G_IO_OUT | G_IO_HUP,
99                                         sifive_uart_xmit, s);
100         if (!r) {
101             fifo8_reset(&s->tx_fifo);
102             return G_SOURCE_REMOVE;
103         }
104     }
105 
106     /* Clear the TX Full bit */
107     if (!fifo8_is_full(&s->tx_fifo)) {
108         s->txfifo &= ~SIFIVE_UART_TXFIFO_FULL;
109     }
110 
111     sifive_uart_update_irq(s);
112     return G_SOURCE_REMOVE;
113 }
114 
115 static void sifive_uart_write_tx_fifo(SiFiveUARTState *s, const uint8_t *buf,
116                                       int size)
117 {
118     uint64_t current_time = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
119 
120     if (size > fifo8_num_free(&s->tx_fifo)) {
121         size = fifo8_num_free(&s->tx_fifo);
122         qemu_log_mask(LOG_GUEST_ERROR, "sifive_uart: TX FIFO overflow");
123     }
124 
125     fifo8_push_all(&s->tx_fifo, buf, size);
126 
127     if (fifo8_is_full(&s->tx_fifo)) {
128         s->txfifo |= SIFIVE_UART_TXFIFO_FULL;
129     }
130 
131     timer_mod(s->fifo_trigger_handle, current_time +
132                   TX_INTERRUPT_TRIGGER_DELAY_NS);
133 }
134 
135 static uint64_t
136 sifive_uart_read(void *opaque, hwaddr addr, unsigned int size)
137 {
138     SiFiveUARTState *s = opaque;
139     unsigned char r;
140     switch (addr) {
141     case SIFIVE_UART_RXFIFO:
142         if (s->rx_fifo_len) {
143             r = s->rx_fifo[0];
144             memmove(s->rx_fifo, s->rx_fifo + 1, s->rx_fifo_len - 1);
145             s->rx_fifo_len--;
146             qemu_chr_fe_accept_input(&s->chr);
147             sifive_uart_update_irq(s);
148             return r;
149         }
150         return 0x80000000;
151 
152     case SIFIVE_UART_TXFIFO:
153         return s->txfifo;
154     case SIFIVE_UART_IE:
155         return s->ie;
156     case SIFIVE_UART_IP:
157         return sifive_uart_ip(s);
158     case SIFIVE_UART_TXCTRL:
159         return s->txctrl;
160     case SIFIVE_UART_RXCTRL:
161         return s->rxctrl;
162     case SIFIVE_UART_DIV:
163         return s->div;
164     }
165 
166     qemu_log_mask(LOG_GUEST_ERROR, "%s: bad read: addr=0x%x\n",
167                   __func__, (int)addr);
168     return 0;
169 }
170 
171 static void
172 sifive_uart_write(void *opaque, hwaddr addr,
173                   uint64_t val64, unsigned int size)
174 {
175     SiFiveUARTState *s = opaque;
176     uint32_t value = val64;
177 
178     switch (addr) {
179     case SIFIVE_UART_TXFIFO:
180         sifive_uart_write_tx_fifo(s, (uint8_t *) &value, 1);
181         return;
182     case SIFIVE_UART_IE:
183         s->ie = val64;
184         sifive_uart_update_irq(s);
185         return;
186     case SIFIVE_UART_TXCTRL:
187         s->txctrl = val64;
188         return;
189     case SIFIVE_UART_RXCTRL:
190         s->rxctrl = val64;
191         return;
192     case SIFIVE_UART_DIV:
193         s->div = val64;
194         return;
195     }
196     qemu_log_mask(LOG_GUEST_ERROR, "%s: bad write: addr=0x%x v=0x%x\n",
197                   __func__, (int)addr, (int)value);
198 }
199 
200 static void fifo_trigger_update(void *opaque)
201 {
202     SiFiveUARTState *s = opaque;
203 
204     sifive_uart_xmit(NULL, G_IO_OUT, s);
205 }
206 
207 static const MemoryRegionOps sifive_uart_ops = {
208     .read = sifive_uart_read,
209     .write = sifive_uart_write,
210     .endianness = DEVICE_NATIVE_ENDIAN,
211     .valid = {
212         .min_access_size = 4,
213         .max_access_size = 4
214     }
215 };
216 
217 static void sifive_uart_rx(void *opaque, const uint8_t *buf, int size)
218 {
219     SiFiveUARTState *s = opaque;
220 
221     /* Got a byte.  */
222     if (s->rx_fifo_len >= sizeof(s->rx_fifo)) {
223         printf("WARNING: UART dropped char.\n");
224         return;
225     }
226     s->rx_fifo[s->rx_fifo_len++] = *buf;
227 
228     sifive_uart_update_irq(s);
229 }
230 
231 static int sifive_uart_can_rx(void *opaque)
232 {
233     SiFiveUARTState *s = opaque;
234 
235     return s->rx_fifo_len < sizeof(s->rx_fifo);
236 }
237 
238 static void sifive_uart_event(void *opaque, QEMUChrEvent event)
239 {
240 }
241 
242 static int sifive_uart_be_change(void *opaque)
243 {
244     SiFiveUARTState *s = opaque;
245 
246     qemu_chr_fe_set_handlers(&s->chr, sifive_uart_can_rx, sifive_uart_rx,
247                              sifive_uart_event, sifive_uart_be_change, s,
248                              NULL, true);
249 
250     return 0;
251 }
252 
253 static Property sifive_uart_properties[] = {
254     DEFINE_PROP_CHR("chardev", SiFiveUARTState, chr),
255     DEFINE_PROP_END_OF_LIST(),
256 };
257 
258 static void sifive_uart_init(Object *obj)
259 {
260     SysBusDevice *sbd = SYS_BUS_DEVICE(obj);
261     SiFiveUARTState *s = SIFIVE_UART(obj);
262 
263     memory_region_init_io(&s->mmio, OBJECT(s), &sifive_uart_ops, s,
264                           TYPE_SIFIVE_UART, SIFIVE_UART_MAX);
265     sysbus_init_mmio(sbd, &s->mmio);
266     sysbus_init_irq(sbd, &s->irq);
267 }
268 
269 static void sifive_uart_realize(DeviceState *dev, Error **errp)
270 {
271     SiFiveUARTState *s = SIFIVE_UART(dev);
272 
273     s->fifo_trigger_handle = timer_new_ns(QEMU_CLOCK_VIRTUAL,
274                                           fifo_trigger_update, s);
275 
276     qemu_chr_fe_set_handlers(&s->chr, sifive_uart_can_rx, sifive_uart_rx,
277                              sifive_uart_event, sifive_uart_be_change, s,
278                              NULL, true);
279 
280 }
281 
282 static void sifive_uart_reset_enter(Object *obj, ResetType type)
283 {
284     SiFiveUARTState *s = SIFIVE_UART(obj);
285 
286     s->txfifo = 0;
287     s->ie = 0;
288     s->ip = 0;
289     s->txctrl = 0;
290     s->rxctrl = 0;
291     s->div = 0;
292 
293     s->rx_fifo_len = 0;
294 
295     memset(s->rx_fifo, 0, SIFIVE_UART_RX_FIFO_SIZE);
296     fifo8_create(&s->tx_fifo, SIFIVE_UART_TX_FIFO_SIZE);
297 }
298 
299 static void sifive_uart_reset_hold(Object *obj, ResetType type)
300 {
301     SiFiveUARTState *s = SIFIVE_UART(obj);
302     qemu_irq_lower(s->irq);
303 }
304 
305 static const VMStateDescription vmstate_sifive_uart = {
306     .name = TYPE_SIFIVE_UART,
307     .version_id = 2,
308     .minimum_version_id = 2,
309     .fields = (const VMStateField[]) {
310         VMSTATE_UINT8_ARRAY(rx_fifo, SiFiveUARTState,
311                             SIFIVE_UART_RX_FIFO_SIZE),
312         VMSTATE_UINT8(rx_fifo_len, SiFiveUARTState),
313         VMSTATE_UINT32(ie, SiFiveUARTState),
314         VMSTATE_UINT32(ip, SiFiveUARTState),
315         VMSTATE_UINT32(txctrl, SiFiveUARTState),
316         VMSTATE_UINT32(rxctrl, SiFiveUARTState),
317         VMSTATE_UINT32(div, SiFiveUARTState),
318         VMSTATE_UINT32(txfifo, SiFiveUARTState),
319         VMSTATE_FIFO8(tx_fifo, SiFiveUARTState),
320         VMSTATE_TIMER_PTR(fifo_trigger_handle, SiFiveUARTState),
321         VMSTATE_END_OF_LIST()
322     },
323 };
324 
325 
326 static void sifive_uart_class_init(ObjectClass *oc, void *data)
327 {
328     DeviceClass *dc = DEVICE_CLASS(oc);
329     ResettableClass *rc = RESETTABLE_CLASS(oc);
330 
331     dc->realize = sifive_uart_realize;
332     dc->vmsd = &vmstate_sifive_uart;
333     rc->phases.enter = sifive_uart_reset_enter;
334     rc->phases.hold  = sifive_uart_reset_hold;
335     device_class_set_props(dc, sifive_uart_properties);
336     set_bit(DEVICE_CATEGORY_INPUT, dc->categories);
337 }
338 
339 static const TypeInfo sifive_uart_info = {
340     .name          = TYPE_SIFIVE_UART,
341     .parent        = TYPE_SYS_BUS_DEVICE,
342     .instance_size = sizeof(SiFiveUARTState),
343     .instance_init = sifive_uart_init,
344     .class_init    = sifive_uart_class_init,
345 };
346 
347 static void sifive_uart_register_types(void)
348 {
349     type_register_static(&sifive_uart_info);
350 }
351 
352 type_init(sifive_uart_register_types)
353 
354 /*
355  * Create UART device.
356  */
357 SiFiveUARTState *sifive_uart_create(MemoryRegion *address_space, hwaddr base,
358     Chardev *chr, qemu_irq irq)
359 {
360     DeviceState *dev;
361     SysBusDevice *s;
362 
363     dev = qdev_new("riscv.sifive.uart");
364     s = SYS_BUS_DEVICE(dev);
365     qdev_prop_set_chr(dev, "chardev", chr);
366     sysbus_realize_and_unref(s, &error_fatal);
367     memory_region_add_subregion(address_space, base,
368                                 sysbus_mmio_get_region(s, 0));
369     sysbus_connect_irq(s, 0, irq);
370 
371     return SIFIVE_UART(dev);
372 }
373