summaryrefslogtreecommitdiff
path: root/hw/char/milkymist-uart.c
blob: d05b82534090e0fcd8449b140dc0f05cca6251f1 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
/*
 *  QEMU model of the Milkymist UART block.
 *
 *  Copyright (c) 2010 Michael Walle <michael@walle.cc>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, see <http://www.gnu.org/licenses/>.
 *
 *
 * Specification available at:
 *   http://www.milkymist.org/socdoc/uart.pdf
 */

#include "hw/hw.h"
#include "hw/sysbus.h"
#include "trace.h"
#include "sysemu/char.h"
#include "qemu/error-report.h"

enum {
    R_RXTX = 0,
    R_DIV,
    R_STAT,
    R_CTRL,
    R_DBG,
    R_MAX
};

enum {
    STAT_THRE   = (1<<0),
    STAT_RX_EVT = (1<<1),
    STAT_TX_EVT = (1<<2),
};

enum {
    CTRL_RX_IRQ_EN = (1<<0),
    CTRL_TX_IRQ_EN = (1<<1),
    CTRL_THRU_EN   = (1<<2),
};

enum {
    DBG_BREAK_EN = (1<<0),
};

#define TYPE_MILKYMIST_UART "milkymist-uart"
#define MILKYMIST_UART(obj) \
    OBJECT_CHECK(MilkymistUartState, (obj), TYPE_MILKYMIST_UART)

struct MilkymistUartState {
    SysBusDevice parent_obj;

    MemoryRegion regs_region;
    CharDriverState *chr;
    qemu_irq irq;

    uint32_t regs[R_MAX];
};
typedef struct MilkymistUartState MilkymistUartState;

static void uart_update_irq(MilkymistUartState *s)
{
    int rx_event = s->regs[R_STAT] & STAT_RX_EVT;
    int tx_event = s->regs[R_STAT] & STAT_TX_EVT;
    int rx_irq_en = s->regs[R_CTRL] & CTRL_RX_IRQ_EN;
    int tx_irq_en = s->regs[R_CTRL] & CTRL_TX_IRQ_EN;

    if ((rx_irq_en && rx_event) || (tx_irq_en && tx_event)) {
        trace_milkymist_uart_raise_irq();
        qemu_irq_raise(s->irq);
    } else {
        trace_milkymist_uart_lower_irq();
        qemu_irq_lower(s->irq);
    }
}

static uint64_t uart_read(void *opaque, hwaddr addr,
                          unsigned size)
{
    MilkymistUartState *s = opaque;
    uint32_t r = 0;

    addr >>= 2;
    switch (addr) {
    case R_RXTX:
        r = s->regs[addr];
        break;
    case R_DIV:
    case R_STAT:
    case R_CTRL:
    case R_DBG:
        r = s->regs[addr];
        break;

    default:
        error_report("milkymist_uart: read access to unknown register 0x"
                TARGET_FMT_plx, addr << 2);
        break;
    }

    trace_milkymist_uart_memory_read(addr << 2, r);

    return r;
}

static void uart_write(void *opaque, hwaddr addr, uint64_t value,
                       unsigned size)
{
    MilkymistUartState *s = opaque;
    unsigned char ch = value;

    trace_milkymist_uart_memory_write(addr, value);

    addr >>= 2;
    switch (addr) {
    case R_RXTX:
        if (s->chr) {
            qemu_chr_fe_write_all(s->chr, &ch, 1);
        }
        s->regs[R_STAT] |= STAT_TX_EVT;
        break;
    case R_DIV:
    case R_CTRL:
    case R_DBG:
        s->regs[addr] = value;
        break;

    case R_STAT:
        /* write one to clear bits */
        s->regs[addr] &= ~(value & (STAT_RX_EVT | STAT_TX_EVT));
        qemu_chr_accept_input(s->chr);
        break;

    default:
        error_report("milkymist_uart: write access to unknown register 0x"
                TARGET_FMT_plx, addr << 2);
        break;
    }

    uart_update_irq(s);
}

static const MemoryRegionOps uart_mmio_ops = {
    .read = uart_read,
    .write = uart_write,
    .valid = {
        .min_access_size = 4,
        .max_access_size = 4,
    },
    .endianness = DEVICE_NATIVE_ENDIAN,
};

static void uart_rx(void *opaque, const uint8_t *buf, int size)
{
    MilkymistUartState *s = opaque;

    assert(!(s->regs[R_STAT] & STAT_RX_EVT));

    s->regs[R_STAT] |= STAT_RX_EVT;
    s->regs[R_RXTX] = *buf;

    uart_update_irq(s);
}

static int uart_can_rx(void *opaque)
{
    MilkymistUartState *s = opaque;

    return !(s->regs[R_STAT] & STAT_RX_EVT);
}

static void uart_event(void *opaque, int event)
{
}

static void milkymist_uart_reset(DeviceState *d)
{
    MilkymistUartState *s = MILKYMIST_UART(d);
    int i;

    for (i = 0; i < R_MAX; i++) {
        s->regs[i] = 0;
    }

    /* THRE is always set */
    s->regs[R_STAT] = STAT_THRE;
}

static void milkymist_uart_realize(DeviceState *dev, Error **errp)
{
    MilkymistUartState *s = MILKYMIST_UART(dev);

    s->chr = qemu_char_get_next_serial();
    if (s->chr) {
        qemu_chr_add_handlers(s->chr, uart_can_rx, uart_rx, uart_event, s);
    }
}

static void milkymist_uart_init(Object *obj)
{
    SysBusDevice *sbd = SYS_BUS_DEVICE(obj);
    MilkymistUartState *s = MILKYMIST_UART(obj);

    sysbus_init_irq(sbd, &s->irq);

    memory_region_init_io(&s->regs_region, OBJECT(s), &uart_mmio_ops, s,
                          "milkymist-uart", R_MAX * 4);
    sysbus_init_mmio(sbd, &s->regs_region);
}

static const VMStateDescription vmstate_milkymist_uart = {
    .name = "milkymist-uart",
    .version_id = 1,
    .minimum_version_id = 1,
    .fields = (VMStateField[]) {
        VMSTATE_UINT32_ARRAY(regs, MilkymistUartState, R_MAX),
        VMSTATE_END_OF_LIST()
    }
};

static void milkymist_uart_class_init(ObjectClass *klass, void *data)
{
    DeviceClass *dc = DEVICE_CLASS(klass);

    dc->realize = milkymist_uart_realize;
    dc->reset = milkymist_uart_reset;
    dc->vmsd = &vmstate_milkymist_uart;
}

static const TypeInfo milkymist_uart_info = {
    .name          = TYPE_MILKYMIST_UART,
    .parent        = TYPE_SYS_BUS_DEVICE,
    .instance_size = sizeof(MilkymistUartState),
    .instance_init = milkymist_uart_init,
    .class_init    = milkymist_uart_class_init,
};

static void milkymist_uart_register_types(void)
{
    type_register_static(&milkymist_uart_info);
}

type_init(milkymist_uart_register_types)