hw/misc/mps2-fpgaio.c

   1 /*
   2  * ARM MPS2 AN505 FPGAIO emulation
   3  *
   4  * Copyright (c) 2018 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 "FPGA system control and I/O" block found
  13  * in the AN505 FPGA image for the MPS2 devboard.
  14  * It is documented in AN505:
  15  * http://infocenter.arm.com/help/topic/com.arm.doc.dai0505b/index.html
  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 "hw/misc/mps2-fpgaio.h"
  27 #include "hw/qdev-properties.h"
  28 #include "qemu/timer.h"
  29
  30 REG32(LED0, 0)
  31 REG32(BUTTON, 8)
  32 REG32(CLK1HZ, 0x10)
  33 REG32(CLK100HZ, 0x14)
  34 REG32(COUNTER, 0x18)
  35 REG32(PRESCALE, 0x1c)
  36 REG32(PSCNTR, 0x20)
  37 REG32(MISC, 0x4c)
  38
  39 static uint32_t counter_from_tickoff(int64_t now, int64_t tick_offset, int frq)
  40 {
  41     return muldiv64(now - tick_offset, frq, NANOSECONDS_PER_SECOND);
  42 }
  43
  44 static int64_t tickoff_from_counter(int64_t now, uint32_t count, int frq)
  45 {
  46     return now - muldiv64(count, NANOSECONDS_PER_SECOND, frq);
  47 }
  48
  49 static void resync_counter(MPS2FPGAIO *s)
  50 {
  51     /*
  52      * Update s->counter and s->pscntr to their true current values
  53      * by calculating how many times PSCNTR has ticked since the
  54      * last time we did a resync.
  55      */
  56     int64_t now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
  57     int64_t elapsed = now - s->pscntr_sync_ticks;
  58
  59     /*
  60      * Round elapsed down to a whole number of PSCNTR ticks, so we don't
  61      * lose time if we do multiple resyncs in a single tick.
  62      */
  63     uint64_t ticks = muldiv64(elapsed, s->prescale_clk, NANOSECONDS_PER_SECOND);
  64
  65     /*
  66      * Work out what PSCNTR and COUNTER have moved to. We assume that
  67      * PSCNTR reloads from PRESCALE one tick-period after it hits zero,
  68      * and that COUNTER increments at the same moment.
  69      */
  70     if (ticks == 0) {
  71         /* We haven't ticked since the last time we were asked */
  72         return;
  73     } else if (ticks < s->pscntr) {
  74         /* We haven't yet reached zero, just reduce the PSCNTR */
  75         s->pscntr -= ticks;
  76     } else {
  77         if (s->prescale == 0) {
  78             /*
  79              * If the reload value is zero then the PSCNTR will stick
  80              * at zero once it reaches it, and so we will increment
  81              * COUNTER every tick after that.
  82              */
  83             s->counter += ticks - s->pscntr;
  84             s->pscntr = 0;
  85         } else {
  86             /*
  87              * This is the complicated bit. This ASCII art diagram gives an
  88              * example with PRESCALE==5 PSCNTR==7:
  89              *
  90              * ticks  0  1  2  3  4  5  6  7  8  9 10 11 12 13 14
  91              * PSCNTR 7  6  5  4  3  2  1  0  5  4  3  2  1  0  5
  92              * cinc                           1                 2
  93              * y            0  1  2  3  4  5  6  7  8  9 10 11 12
  94              * x            0  1  2  3  4  5  0  1  2  3  4  5  0
  95              *
  96              * where x = y % (s->prescale + 1)
  97              * and so PSCNTR = s->prescale - x
  98              * and COUNTER is incremented by y / (s->prescale + 1)
  99              *
 100              * The case where PSCNTR < PRESCALE works out the same,
 101              * though we must be careful to calculate y as 64-bit unsigned
 102              * for all parts of the expression.
 103              * y < 0 is not possible because that implies ticks < s->pscntr.
 104              */
 105             uint64_t y = ticks - s->pscntr + s->prescale;
 106             s->pscntr = s->prescale - (y % (s->prescale + 1));
 107             s->counter += y / (s->prescale + 1);
 108         }
 109     }
 110
 111     /*
 112      * Only advance the sync time to the timestamp of the last PSCNTR tick,
 113      * not all the way to 'now', so we don't lose time if we do multiple
 114      * resyncs in a single tick.
 115      */
 116     s->pscntr_sync_ticks += muldiv64(ticks, NANOSECONDS_PER_SECOND,
 117                                      s->prescale_clk);
 118 }
 119
 120 static uint64_t mps2_fpgaio_read(void *opaque, hwaddr offset, unsigned size)
 121 {
 122     MPS2FPGAIO *s = MPS2_FPGAIO(opaque);
 123     uint64_t r;
 124     int64_t now;
 125
 126     switch (offset) {
 127     case A_LED0:
 128         r = s->led0;
 129         break;
 130     case A_BUTTON:
 131         /* User-pressable board buttons. We don't model that, so just return
 132          * zeroes.
 133          */
 134         r = 0;
 135         break;
 136     case A_PRESCALE:
 137         r = s->prescale;
 138         break;
 139     case A_MISC:
 140         r = s->misc;
 141         break;
 142     case A_CLK1HZ:
 143         now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
 144         r = counter_from_tickoff(now, s->clk1hz_tick_offset, 1);
 145         break;
 146     case A_CLK100HZ:
 147         now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
 148         r = counter_from_tickoff(now, s->clk100hz_tick_offset, 100);
 149         break;
 150     case A_COUNTER:
 151         resync_counter(s);
 152         r = s->counter;
 153         break;
 154     case A_PSCNTR:
 155         resync_counter(s);
 156         r = s->pscntr;
 157         break;
 158     default:
 159         qemu_log_mask(LOG_GUEST_ERROR,
 160                       "MPS2 FPGAIO read: bad offset %x\n", (int) offset);
 161         r = 0;
 162         break;
 163     }
 164
 165     trace_mps2_fpgaio_read(offset, r, size);
 166     return r;
 167 }
 168
 169 static void mps2_fpgaio_write(void *opaque, hwaddr offset, uint64_t value,
 170                               unsigned size)
 171 {
 172     MPS2FPGAIO *s = MPS2_FPGAIO(opaque);
 173     int64_t now;
 174
 175     trace_mps2_fpgaio_write(offset, value, size);
 176
 177     switch (offset) {
 178     case A_LED0:
 179         /* LED bits [1:0] control board LEDs. We don't currently have
 180          * a mechanism for displaying this graphically, so use a trace event.
 181          */
 182         trace_mps2_fpgaio_leds(value & 0x02 ? '*' : '.',
 183                                value & 0x01 ? '*' : '.');
 184         s->led0 = value & 0x3;
 185         break;
 186     case A_PRESCALE:
 187         resync_counter(s);
 188         s->prescale = value;
 189         break;
 190     case A_MISC:
 191         /* These are control bits for some of the other devices on the
 192          * board (SPI, CLCD, etc). We don't implement that yet, so just
 193          * make the bits read as written.
 194          */
 195         qemu_log_mask(LOG_UNIMP,
 196                       "MPS2 FPGAIO: MISC control bits unimplemented\n");
 197         s->misc = value;
 198         break;
 199     case A_CLK1HZ:
 200         now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
 201         s->clk1hz_tick_offset = tickoff_from_counter(now, value, 1);
 202         break;
 203     case A_CLK100HZ:
 204         now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
 205         s->clk100hz_tick_offset = tickoff_from_counter(now, value, 100);
 206         break;
 207     case A_COUNTER:
 208         resync_counter(s);
 209         s->counter = value;
 210         break;
 211     case A_PSCNTR:
 212         resync_counter(s);
 213         s->pscntr = value;
 214         break;
 215     default:
 216         qemu_log_mask(LOG_GUEST_ERROR,
 217                       "MPS2 FPGAIO write: bad offset 0x%x\n", (int) offset);
 218         break;
 219     }
 220 }
 221
 222 static const MemoryRegionOps mps2_fpgaio_ops = {
 223     .read = mps2_fpgaio_read,
 224     .write = mps2_fpgaio_write,
 225     .endianness = DEVICE_LITTLE_ENDIAN,
 226 };
 227
 228 static void mps2_fpgaio_reset(DeviceState *dev)
 229 {
 230     MPS2FPGAIO *s = MPS2_FPGAIO(dev);
 231     int64_t now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
 232
 233     trace_mps2_fpgaio_reset();
 234     s->led0 = 0;
 235     s->prescale = 0;
 236     s->misc = 0;
 237     s->clk1hz_tick_offset = tickoff_from_counter(now, 0, 1);
 238     s->clk100hz_tick_offset = tickoff_from_counter(now, 0, 100);
 239     s->counter = 0;
 240     s->pscntr = 0;
 241     s->pscntr_sync_ticks = now;
 242 }
 243
 244 static void mps2_fpgaio_init(Object *obj)
 245 {
 246     SysBusDevice *sbd = SYS_BUS_DEVICE(obj);
 247     MPS2FPGAIO *s = MPS2_FPGAIO(obj);
 248
 249     memory_region_init_io(&s->iomem, obj, &mps2_fpgaio_ops, s,
 250                           "mps2-fpgaio", 0x1000);
 251     sysbus_init_mmio(sbd, &s->iomem);
 252 }
 253
 254 static bool mps2_fpgaio_counters_needed(void *opaque)
 255 {
 256     /* Currently vmstate.c insists all subsections have a 'needed' function */
 257     return true;
 258 }
 259
 260 static const VMStateDescription mps2_fpgaio_counters_vmstate = {
 261     .name = "mps2-fpgaio/counters",
 262     .version_id = 2,
 263     .minimum_version_id = 2,
 264     .needed = mps2_fpgaio_counters_needed,
 265     .fields = (VMStateField[]) {
 266         VMSTATE_INT64(clk1hz_tick_offset, MPS2FPGAIO),
 267         VMSTATE_INT64(clk100hz_tick_offset, MPS2FPGAIO),
 268         VMSTATE_UINT32(counter, MPS2FPGAIO),
 269         VMSTATE_UINT32(pscntr, MPS2FPGAIO),
 270         VMSTATE_INT64(pscntr_sync_ticks, MPS2FPGAIO),
 271         VMSTATE_END_OF_LIST()
 272     }
 273 };
 274
 275 static const VMStateDescription mps2_fpgaio_vmstate = {
 276     .name = "mps2-fpgaio",
 277     .version_id = 1,
 278     .minimum_version_id = 1,
 279     .fields = (VMStateField[]) {
 280         VMSTATE_UINT32(led0, MPS2FPGAIO),
 281         VMSTATE_UINT32(prescale, MPS2FPGAIO),
 282         VMSTATE_UINT32(misc, MPS2FPGAIO),
 283         VMSTATE_END_OF_LIST()
 284     },
 285     .subsections = (const VMStateDescription*[]) {
 286         &mps2_fpgaio_counters_vmstate,
 287         NULL
 288     }
 289 };
 290
 291 static Property mps2_fpgaio_properties[] = {
 292     /* Frequency of the prescale counter */
 293     DEFINE_PROP_UINT32("prescale-clk", MPS2FPGAIO, prescale_clk, 20000000),
 294     DEFINE_PROP_END_OF_LIST(),
 295 };
 296
 297 static void mps2_fpgaio_class_init(ObjectClass *klass, void *data)
 298 {
 299     DeviceClass *dc = DEVICE_CLASS(klass);
 300
 301     dc->vmsd = &mps2_fpgaio_vmstate;
 302     dc->reset = mps2_fpgaio_reset;
 303     dc->props = mps2_fpgaio_properties;
 304 }
 305
 306 static const TypeInfo mps2_fpgaio_info = {
 307     .name = TYPE_MPS2_FPGAIO,
 308     .parent = TYPE_SYS_BUS_DEVICE,
 309     .instance_size = sizeof(MPS2FPGAIO),
 310     .instance_init = mps2_fpgaio_init,
 311     .class_init = mps2_fpgaio_class_init,
 312 };
 313
 314 static void mps2_fpgaio_register_types(void)
 315 {
 316     type_register_static(&mps2_fpgaio_info);
 317 }
 318
 319 type_init(mps2_fpgaio_register_types);