hw/timer/cmsdk-apb-timer.c

   1 /*
   2  * ARM CMSDK APB timer emulation
   3  *
   4  * Copyright (c) 2017 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 "APB timer" which is part of the Cortex-M
  13  * System Design Kit (CMSDK) and documented in the Cortex-M System
  14  * Design Kit Technical Reference Manual (ARM DDI0479C):
  15  * https://developer.arm.com/products/system-design/system-design-kits/cortex-m-system-design-kit
  16  *
  17  * The hardware has an EXTIN input wire, which can be configured
  18  * by the guest to act either as a 'timer enable' (timer does not run
  19  * when EXTIN is low), or as a 'timer clock' (timer runs at frequency
  20  * of EXTIN clock, not PCLK frequency). We don't model this.
  21  *
  22  * The documentation is not very clear about the exact behaviour;
  23  * we choose to implement that the interrupt is triggered when
  24  * the counter goes from 1 to 0, that the counter then holds at 0
  25  * for one clock cycle before reloading from the RELOAD register,
  26  * and that if the RELOAD register is 0 this does not cause an
  27  * interrupt (as there is no further 1->0 transition).
  28  */
  29
  30 #include "qemu/osdep.h"
  31 #include "qemu/log.h"
  32 #include "qemu/main-loop.h"
  33 #include "qemu/module.h"
  34 #include "qapi/error.h"
  35 #include "trace.h"
  36 #include "hw/sysbus.h"
  37 #include "hw/irq.h"
  38 #include "hw/registerfields.h"
  39 #include "hw/timer/cmsdk-apb-timer.h"
  40 #include "migration/vmstate.h"
  41
  42 REG32(CTRL, 0)
  43     FIELD(CTRL, EN, 0, 1)
  44     FIELD(CTRL, SELEXTEN, 1, 1)
  45     FIELD(CTRL, SELEXTCLK, 2, 1)
  46     FIELD(CTRL, IRQEN, 3, 1)
  47 REG32(VALUE, 4)
  48 REG32(RELOAD, 8)
  49 REG32(INTSTATUS, 0xc)
  50     FIELD(INTSTATUS, IRQ, 0, 1)
  51 REG32(PID4, 0xFD0)
  52 REG32(PID5, 0xFD4)
  53 REG32(PID6, 0xFD8)
  54 REG32(PID7, 0xFDC)
  55 REG32(PID0, 0xFE0)
  56 REG32(PID1, 0xFE4)
  57 REG32(PID2, 0xFE8)
  58 REG32(PID3, 0xFEC)
  59 REG32(CID0, 0xFF0)
  60 REG32(CID1, 0xFF4)
  61 REG32(CID2, 0xFF8)
  62 REG32(CID3, 0xFFC)
  63
  64 /* PID/CID values */
  65 static const int timer_id[] = {
  66     0x04, 0x00, 0x00, 0x00, /* PID4..PID7 */
  67     0x22, 0xb8, 0x1b, 0x00, /* PID0..PID3 */
  68     0x0d, 0xf0, 0x05, 0xb1, /* CID0..CID3 */
  69 };
  70
  71 static void cmsdk_apb_timer_update(CMSDKAPBTIMER *s)
  72 {
  73     qemu_set_irq(s->timerint, !!(s->intstatus & R_INTSTATUS_IRQ_MASK));
  74 }
  75
  76 static uint64_t cmsdk_apb_timer_read(void *opaque, hwaddr offset, unsigned size)
  77 {
  78     CMSDKAPBTIMER *s = CMSDK_APB_TIMER(opaque);
  79     uint64_t r;
  80
  81     switch (offset) {
  82     case A_CTRL:
  83         r = s->ctrl;
  84         break;
  85     case A_VALUE:
  86         r = ptimer_get_count(s->timer);
  87         break;
  88     case A_RELOAD:
  89         r = ptimer_get_limit(s->timer);
  90         break;
  91     case A_INTSTATUS:
  92         r = s->intstatus;
  93         break;
  94     case A_PID4 ... A_CID3:
  95         r = timer_id[(offset - A_PID4) / 4];
  96         break;
  97     default:
  98         qemu_log_mask(LOG_GUEST_ERROR,
  99                       "CMSDK APB timer read: bad offset %x\n", (int) offset);
 100         r = 0;
 101         break;
 102     }
 103     trace_cmsdk_apb_timer_read(offset, r, size);
 104     return r;
 105 }
 106
 107 static void cmsdk_apb_timer_write(void *opaque, hwaddr offset, uint64_t value,
 108                                   unsigned size)
 109 {
 110     CMSDKAPBTIMER *s = CMSDK_APB_TIMER(opaque);
 111
 112     trace_cmsdk_apb_timer_write(offset, value, size);
 113
 114     switch (offset) {
 115     case A_CTRL:
 116         if (value & 6) {
 117             /* Bits [1] and [2] enable using EXTIN as either clock or
 118              * an enable line. We don't model this.
 119              */
 120             qemu_log_mask(LOG_UNIMP,
 121                           "CMSDK APB timer: EXTIN input not supported\n");
 122         }
 123         s->ctrl = value & 0xf;
 124         if (s->ctrl & R_CTRL_EN_MASK) {
 125             ptimer_run(s->timer, ptimer_get_limit(s->timer) == 0);
 126         } else {
 127             ptimer_stop(s->timer);
 128         }
 129         break;
 130     case A_RELOAD:
 131         /* Writing to reload also sets the current timer value */
 132         if (!value) {
 133             ptimer_stop(s->timer);
 134         }
 135         ptimer_set_limit(s->timer, value, 1);
 136         if (value && (s->ctrl & R_CTRL_EN_MASK)) {
 137             /*
 138              * Make sure timer is running (it might have stopped if this
 139              * was an expired one-shot timer)
 140              */
 141             ptimer_run(s->timer, 0);
 142         }
 143         break;
 144     case A_VALUE:
 145         if (!value && !ptimer_get_limit(s->timer)) {
 146             ptimer_stop(s->timer);
 147         }
 148         ptimer_set_count(s->timer, value);
 149         if (value && (s->ctrl & R_CTRL_EN_MASK)) {
 150             ptimer_run(s->timer, ptimer_get_limit(s->timer) == 0);
 151         }
 152         break;
 153     case A_INTSTATUS:
 154         /* Just one bit, which is W1C. */
 155         value &= 1;
 156         s->intstatus &= ~value;
 157         cmsdk_apb_timer_update(s);
 158         break;
 159     case A_PID4 ... A_CID3:
 160         qemu_log_mask(LOG_GUEST_ERROR,
 161                       "CMSDK APB timer write: write to RO offset 0x%x\n",
 162                       (int)offset);
 163         break;
 164     default:
 165         qemu_log_mask(LOG_GUEST_ERROR,
 166                       "CMSDK APB timer write: bad offset 0x%x\n", (int) offset);
 167         break;
 168     }
 169 }
 170
 171 static const MemoryRegionOps cmsdk_apb_timer_ops = {
 172     .read = cmsdk_apb_timer_read,
 173     .write = cmsdk_apb_timer_write,
 174     .endianness = DEVICE_LITTLE_ENDIAN,
 175 };
 176
 177 static void cmsdk_apb_timer_tick(void *opaque)
 178 {
 179     CMSDKAPBTIMER *s = CMSDK_APB_TIMER(opaque);
 180
 181     if (s->ctrl & R_CTRL_IRQEN_MASK) {
 182         s->intstatus |= R_INTSTATUS_IRQ_MASK;
 183         cmsdk_apb_timer_update(s);
 184     }
 185 }
 186
 187 static void cmsdk_apb_timer_reset(DeviceState *dev)
 188 {
 189     CMSDKAPBTIMER *s = CMSDK_APB_TIMER(dev);
 190
 191     trace_cmsdk_apb_timer_reset();
 192     s->ctrl = 0;
 193     s->intstatus = 0;
 194     ptimer_stop(s->timer);
 195     /* Set the limit and the count */
 196     ptimer_set_limit(s->timer, 0, 1);
 197 }
 198
 199 static void cmsdk_apb_timer_init(Object *obj)
 200 {
 201     SysBusDevice *sbd = SYS_BUS_DEVICE(obj);
 202     CMSDKAPBTIMER *s = CMSDK_APB_TIMER(obj);
 203
 204     memory_region_init_io(&s->iomem, obj, &cmsdk_apb_timer_ops,
 205                           s, "cmsdk-apb-timer", 0x1000);
 206     sysbus_init_mmio(sbd, &s->iomem);
 207     sysbus_init_irq(sbd, &s->timerint);
 208 }
 209
 210 static void cmsdk_apb_timer_realize(DeviceState *dev, Error **errp)
 211 {
 212     CMSDKAPBTIMER *s = CMSDK_APB_TIMER(dev);
 213     QEMUBH *bh;
 214
 215     if (s->pclk_frq == 0) {
 216         error_setg(errp, "CMSDK APB timer: pclk-frq property must be set");
 217         return;
 218     }
 219
 220     bh = qemu_bh_new(cmsdk_apb_timer_tick, s);
 221     s->timer = ptimer_init(bh,
 222                            PTIMER_POLICY_WRAP_AFTER_ONE_PERIOD |
 223                            PTIMER_POLICY_TRIGGER_ONLY_ON_DECREMENT |
 224                            PTIMER_POLICY_NO_IMMEDIATE_RELOAD |
 225                            PTIMER_POLICY_NO_COUNTER_ROUND_DOWN);
 226
 227     ptimer_set_freq(s->timer, s->pclk_frq);
 228 }
 229
 230 static const VMStateDescription cmsdk_apb_timer_vmstate = {
 231     .name = "cmsdk-apb-timer",
 232     .version_id = 1,
 233     .minimum_version_id = 1,
 234     .fields = (VMStateField[]) {
 235         VMSTATE_PTIMER(timer, CMSDKAPBTIMER),
 236         VMSTATE_UINT32(ctrl, CMSDKAPBTIMER),
 237         VMSTATE_UINT32(value, CMSDKAPBTIMER),
 238         VMSTATE_UINT32(reload, CMSDKAPBTIMER),
 239         VMSTATE_UINT32(intstatus, CMSDKAPBTIMER),
 240         VMSTATE_END_OF_LIST()
 241     }
 242 };
 243
 244 static Property cmsdk_apb_timer_properties[] = {
 245     DEFINE_PROP_UINT32("pclk-frq", CMSDKAPBTIMER, pclk_frq, 0),
 246     DEFINE_PROP_END_OF_LIST(),
 247 };
 248
 249 static void cmsdk_apb_timer_class_init(ObjectClass *klass, void *data)
 250 {
 251     DeviceClass *dc = DEVICE_CLASS(klass);
 252
 253     dc->realize = cmsdk_apb_timer_realize;
 254     dc->vmsd = &cmsdk_apb_timer_vmstate;
 255     dc->reset = cmsdk_apb_timer_reset;
 256     dc->props = cmsdk_apb_timer_properties;
 257 }
 258
 259 static const TypeInfo cmsdk_apb_timer_info = {
 260     .name = TYPE_CMSDK_APB_TIMER,
 261     .parent = TYPE_SYS_BUS_DEVICE,
 262     .instance_size = sizeof(CMSDKAPBTIMER),
 263     .instance_init = cmsdk_apb_timer_init,
 264     .class_init = cmsdk_apb_timer_class_init,
 265 };
 266
 267 static void cmsdk_apb_timer_register_types(void)
 268 {
 269     type_register_static(&cmsdk_apb_timer_info);
 270 }
 271
 272 type_init(cmsdk_apb_timer_register_types);