aboutsummaryrefslogtreecommitdiff
path: root/hw/misc/mps2-fpgaio.c
blob: 4824dc09b28b5538e8b409ba3d5f11f63748a319 (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
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
/*
 * ARM MPS2 AN505 FPGAIO emulation
 *
 * Copyright (c) 2018 Linaro Limited
 * Written by Peter Maydell
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 2 or
 *  (at your option) any later version.
 */

/* This is a model of the "FPGA system control and I/O" block found
 * in the AN505 FPGA image for the MPS2 devboard.
 * It is documented in AN505:
 * http://infocenter.arm.com/help/topic/com.arm.doc.dai0505b/index.html
 */

#include "qemu/osdep.h"
#include "qemu/log.h"
#include "qemu/module.h"
#include "qapi/error.h"
#include "trace.h"
#include "hw/sysbus.h"
#include "migration/vmstate.h"
#include "hw/registerfields.h"
#include "hw/misc/mps2-fpgaio.h"
#include "qemu/timer.h"

REG32(LED0, 0)
REG32(BUTTON, 8)
REG32(CLK1HZ, 0x10)
REG32(CLK100HZ, 0x14)
REG32(COUNTER, 0x18)
REG32(PRESCALE, 0x1c)
REG32(PSCNTR, 0x20)
REG32(MISC, 0x4c)

static uint32_t counter_from_tickoff(int64_t now, int64_t tick_offset, int frq)
{
    return muldiv64(now - tick_offset, frq, NANOSECONDS_PER_SECOND);
}

static int64_t tickoff_from_counter(int64_t now, uint32_t count, int frq)
{
    return now - muldiv64(count, NANOSECONDS_PER_SECOND, frq);
}

static void resync_counter(MPS2FPGAIO *s)
{
    /*
     * Update s->counter and s->pscntr to their true current values
     * by calculating how many times PSCNTR has ticked since the
     * last time we did a resync.
     */
    int64_t now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
    int64_t elapsed = now - s->pscntr_sync_ticks;

    /*
     * Round elapsed down to a whole number of PSCNTR ticks, so we don't
     * lose time if we do multiple resyncs in a single tick.
     */
    uint64_t ticks = muldiv64(elapsed, s->prescale_clk, NANOSECONDS_PER_SECOND);

    /*
     * Work out what PSCNTR and COUNTER have moved to. We assume that
     * PSCNTR reloads from PRESCALE one tick-period after it hits zero,
     * and that COUNTER increments at the same moment.
     */
    if (ticks == 0) {
        /* We haven't ticked since the last time we were asked */
        return;
    } else if (ticks < s->pscntr) {
        /* We haven't yet reached zero, just reduce the PSCNTR */
        s->pscntr -= ticks;
    } else {
        if (s->prescale == 0) {
            /*
             * If the reload value is zero then the PSCNTR will stick
             * at zero once it reaches it, and so we will increment
             * COUNTER every tick after that.
             */
            s->counter += ticks - s->pscntr;
            s->pscntr = 0;
        } else {
            /*
             * This is the complicated bit. This ASCII art diagram gives an
             * example with PRESCALE==5 PSCNTR==7:
             *
             * ticks  0  1  2  3  4  5  6  7  8  9 10 11 12 13 14
             * PSCNTR 7  6  5  4  3  2  1  0  5  4  3  2  1  0  5
             * cinc                           1                 2
             * y            0  1  2  3  4  5  6  7  8  9 10 11 12
             * x            0  1  2  3  4  5  0  1  2  3  4  5  0
             *
             * where x = y % (s->prescale + 1)
             * and so PSCNTR = s->prescale - x
             * and COUNTER is incremented by y / (s->prescale + 1)
             *
             * The case where PSCNTR < PRESCALE works out the same,
             * though we must be careful to calculate y as 64-bit unsigned
             * for all parts of the expression.
             * y < 0 is not possible because that implies ticks < s->pscntr.
             */
            uint64_t y = ticks - s->pscntr + s->prescale;
            s->pscntr = s->prescale - (y % (s->prescale + 1));
            s->counter += y / (s->prescale + 1);
        }
    }

    /*
     * Only advance the sync time to the timestamp of the last PSCNTR tick,
     * not all the way to 'now', so we don't lose time if we do multiple
     * resyncs in a single tick.
     */
    s->pscntr_sync_ticks += muldiv64(ticks, NANOSECONDS_PER_SECOND,
                                     s->prescale_clk);
}

static uint64_t mps2_fpgaio_read(void *opaque, hwaddr offset, unsigned size)
{
    MPS2FPGAIO *s = MPS2_FPGAIO(opaque);
    uint64_t r;
    int64_t now;

    switch (offset) {
    case A_LED0:
        r = s->led0;
        break;
    case A_BUTTON:
        /* User-pressable board buttons. We don't model that, so just return
         * zeroes.
         */
        r = 0;
        break;
    case A_PRESCALE:
        r = s->prescale;
        break;
    case A_MISC:
        r = s->misc;
        break;
    case A_CLK1HZ:
        now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
        r = counter_from_tickoff(now, s->clk1hz_tick_offset, 1);
        break;
    case A_CLK100HZ:
        now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
        r = counter_from_tickoff(now, s->clk100hz_tick_offset, 100);
        break;
    case A_COUNTER:
        resync_counter(s);
        r = s->counter;
        break;
    case A_PSCNTR:
        resync_counter(s);
        r = s->pscntr;
        break;
    default:
        qemu_log_mask(LOG_GUEST_ERROR,
                      "MPS2 FPGAIO read: bad offset %x\n", (int) offset);
        r = 0;
        break;
    }

    trace_mps2_fpgaio_read(offset, r, size);
    return r;
}

static void mps2_fpgaio_write(void *opaque, hwaddr offset, uint64_t value,
                              unsigned size)
{
    MPS2FPGAIO *s = MPS2_FPGAIO(opaque);
    int64_t now;

    trace_mps2_fpgaio_write(offset, value, size);

    switch (offset) {
    case A_LED0:
        /* LED bits [1:0] control board LEDs. We don't currently have
         * a mechanism for displaying this graphically, so use a trace event.
         */
        trace_mps2_fpgaio_leds(value & 0x02 ? '*' : '.',
                               value & 0x01 ? '*' : '.');
        s->led0 = value & 0x3;
        break;
    case A_PRESCALE:
        resync_counter(s);
        s->prescale = value;
        break;
    case A_MISC:
        /* These are control bits for some of the other devices on the
         * board (SPI, CLCD, etc). We don't implement that yet, so just
         * make the bits read as written.
         */
        qemu_log_mask(LOG_UNIMP,
                      "MPS2 FPGAIO: MISC control bits unimplemented\n");
        s->misc = value;
        break;
    case A_CLK1HZ:
        now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
        s->clk1hz_tick_offset = tickoff_from_counter(now, value, 1);
        break;
    case A_CLK100HZ:
        now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
        s->clk100hz_tick_offset = tickoff_from_counter(now, value, 100);
        break;
    case A_COUNTER:
        resync_counter(s);
        s->counter = value;
        break;
    case A_PSCNTR:
        resync_counter(s);
        s->pscntr = value;
        break;
    default:
        qemu_log_mask(LOG_GUEST_ERROR,
                      "MPS2 FPGAIO write: bad offset 0x%x\n", (int) offset);
        break;
    }
}

static const MemoryRegionOps mps2_fpgaio_ops = {
    .read = mps2_fpgaio_read,
    .write = mps2_fpgaio_write,
    .endianness = DEVICE_LITTLE_ENDIAN,
};

static void mps2_fpgaio_reset(DeviceState *dev)
{
    MPS2FPGAIO *s = MPS2_FPGAIO(dev);
    int64_t now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);

    trace_mps2_fpgaio_reset();
    s->led0 = 0;
    s->prescale = 0;
    s->misc = 0;
    s->clk1hz_tick_offset = tickoff_from_counter(now, 0, 1);
    s->clk100hz_tick_offset = tickoff_from_counter(now, 0, 100);
    s->counter = 0;
    s->pscntr = 0;
    s->pscntr_sync_ticks = now;
}

static void mps2_fpgaio_init(Object *obj)
{
    SysBusDevice *sbd = SYS_BUS_DEVICE(obj);
    MPS2FPGAIO *s = MPS2_FPGAIO(obj);

    memory_region_init_io(&s->iomem, obj, &mps2_fpgaio_ops, s,
                          "mps2-fpgaio", 0x1000);
    sysbus_init_mmio(sbd, &s->iomem);
}

static bool mps2_fpgaio_counters_needed(void *opaque)
{
    /* Currently vmstate.c insists all subsections have a 'needed' function */
    return true;
}

static const VMStateDescription mps2_fpgaio_counters_vmstate = {
    .name = "mps2-fpgaio/counters",
    .version_id = 2,
    .minimum_version_id = 2,
    .needed = mps2_fpgaio_counters_needed,
    .fields = (VMStateField[]) {
        VMSTATE_INT64(clk1hz_tick_offset, MPS2FPGAIO),
        VMSTATE_INT64(clk100hz_tick_offset, MPS2FPGAIO),
        VMSTATE_UINT32(counter, MPS2FPGAIO),
        VMSTATE_UINT32(pscntr, MPS2FPGAIO),
        VMSTATE_INT64(pscntr_sync_ticks, MPS2FPGAIO),
        VMSTATE_END_OF_LIST()
    }
};

static const VMStateDescription mps2_fpgaio_vmstate = {
    .name = "mps2-fpgaio",
    .version_id = 1,
    .minimum_version_id = 1,
    .fields = (VMStateField[]) {
        VMSTATE_UINT32(led0, MPS2FPGAIO),
        VMSTATE_UINT32(prescale, MPS2FPGAIO),
        VMSTATE_UINT32(misc, MPS2FPGAIO),
        VMSTATE_END_OF_LIST()
    },
    .subsections = (const VMStateDescription*[]) {
        &mps2_fpgaio_counters_vmstate,
        NULL
    }
};

static Property mps2_fpgaio_properties[] = {
    /* Frequency of the prescale counter */
    DEFINE_PROP_UINT32("prescale-clk", MPS2FPGAIO, prescale_clk, 20000000),
    DEFINE_PROP_END_OF_LIST(),
};

static void mps2_fpgaio_class_init(ObjectClass *klass, void *data)
{
    DeviceClass *dc = DEVICE_CLASS(klass);

    dc->vmsd = &mps2_fpgaio_vmstate;
    dc->reset = mps2_fpgaio_reset;
    dc->props = mps2_fpgaio_properties;
}

static const TypeInfo mps2_fpgaio_info = {
    .name = TYPE_MPS2_FPGAIO,
    .parent = TYPE_SYS_BUS_DEVICE,
    .instance_size = sizeof(MPS2FPGAIO),
    .instance_init = mps2_fpgaio_init,
    .class_init = mps2_fpgaio_class_init,
};

static void mps2_fpgaio_register_types(void)
{
    type_register_static(&mps2_fpgaio_info);
}

type_init(mps2_fpgaio_register_types);