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/module.h" 33 #include "qapi/error.h" 34 #include "trace.h" 35 #include "hw/sysbus.h" 36 #include "hw/irq.h" 37 #include "hw/registerfields.h" 38 #include "hw/timer/cmsdk-apb-timer.h" 39 #include "migration/vmstate.h" 40 41 REG32(CTRL, 0) 42 FIELD(CTRL, EN, 0, 1) 43 FIELD(CTRL, SELEXTEN, 1, 1) 44 FIELD(CTRL, SELEXTCLK, 2, 1) 45 FIELD(CTRL, IRQEN, 3, 1) 46 REG32(VALUE, 4) 47 REG32(RELOAD, 8) 48 REG32(INTSTATUS, 0xc) 49 FIELD(INTSTATUS, IRQ, 0, 1) 50 REG32(PID4, 0xFD0) 51 REG32(PID5, 0xFD4) 52 REG32(PID6, 0xFD8) 53 REG32(PID7, 0xFDC) 54 REG32(PID0, 0xFE0) 55 REG32(PID1, 0xFE4) 56 REG32(PID2, 0xFE8) 57 REG32(PID3, 0xFEC) 58 REG32(CID0, 0xFF0) 59 REG32(CID1, 0xFF4) 60 REG32(CID2, 0xFF8) 61 REG32(CID3, 0xFFC) 62 63 /* PID/CID values */ 64 static const int timer_id[] = { 65 0x04, 0x00, 0x00, 0x00, /* PID4..PID7 */ 66 0x22, 0xb8, 0x1b, 0x00, /* PID0..PID3 */ 67 0x0d, 0xf0, 0x05, 0xb1, /* CID0..CID3 */ 68 }; 69 70 static void cmsdk_apb_timer_update(CMSDKAPBTIMER *s) 71 { 72 qemu_set_irq(s->timerint, !!(s->intstatus & R_INTSTATUS_IRQ_MASK)); 73 } 74 75 static uint64_t cmsdk_apb_timer_read(void *opaque, hwaddr offset, unsigned size) 76 { 77 CMSDKAPBTIMER *s = CMSDK_APB_TIMER(opaque); 78 uint64_t r; 79 80 switch (offset) { 81 case A_CTRL: 82 r = s->ctrl; 83 break; 84 case A_VALUE: 85 r = ptimer_get_count(s->timer); 86 break; 87 case A_RELOAD: 88 r = ptimer_get_limit(s->timer); 89 break; 90 case A_INTSTATUS: 91 r = s->intstatus; 92 break; 93 case A_PID4 ... A_CID3: 94 r = timer_id[(offset - A_PID4) / 4]; 95 break; 96 default: 97 qemu_log_mask(LOG_GUEST_ERROR, 98 "CMSDK APB timer read: bad offset %x\n", (int) offset); 99 r = 0; 100 break; 101 } 102 trace_cmsdk_apb_timer_read(offset, r, size); 103 return r; 104 } 105 106 static void cmsdk_apb_timer_write(void *opaque, hwaddr offset, uint64_t value, 107 unsigned size) 108 { 109 CMSDKAPBTIMER *s = CMSDK_APB_TIMER(opaque); 110 111 trace_cmsdk_apb_timer_write(offset, value, size); 112 113 switch (offset) { 114 case A_CTRL: 115 if (value & 6) { 116 /* Bits [1] and [2] enable using EXTIN as either clock or 117 * an enable line. We don't model this. 118 */ 119 qemu_log_mask(LOG_UNIMP, 120 "CMSDK APB timer: EXTIN input not supported\n"); 121 } 122 s->ctrl = value & 0xf; 123 ptimer_transaction_begin(s->timer); 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 ptimer_transaction_commit(s->timer); 130 break; 131 case A_RELOAD: 132 /* Writing to reload also sets the current timer value */ 133 ptimer_transaction_begin(s->timer); 134 if (!value) { 135 ptimer_stop(s->timer); 136 } 137 ptimer_set_limit(s->timer, value, 1); 138 if (value && (s->ctrl & R_CTRL_EN_MASK)) { 139 /* 140 * Make sure timer is running (it might have stopped if this 141 * was an expired one-shot timer) 142 */ 143 ptimer_run(s->timer, 0); 144 } 145 ptimer_transaction_commit(s->timer); 146 break; 147 case A_VALUE: 148 ptimer_transaction_begin(s->timer); 149 if (!value && !ptimer_get_limit(s->timer)) { 150 ptimer_stop(s->timer); 151 } 152 ptimer_set_count(s->timer, value); 153 if (value && (s->ctrl & R_CTRL_EN_MASK)) { 154 ptimer_run(s->timer, ptimer_get_limit(s->timer) == 0); 155 } 156 ptimer_transaction_commit(s->timer); 157 break; 158 case A_INTSTATUS: 159 /* Just one bit, which is W1C. */ 160 value &= 1; 161 s->intstatus &= ~value; 162 cmsdk_apb_timer_update(s); 163 break; 164 case A_PID4 ... A_CID3: 165 qemu_log_mask(LOG_GUEST_ERROR, 166 "CMSDK APB timer write: write to RO offset 0x%x\n", 167 (int)offset); 168 break; 169 default: 170 qemu_log_mask(LOG_GUEST_ERROR, 171 "CMSDK APB timer write: bad offset 0x%x\n", (int) offset); 172 break; 173 } 174 } 175 176 static const MemoryRegionOps cmsdk_apb_timer_ops = { 177 .read = cmsdk_apb_timer_read, 178 .write = cmsdk_apb_timer_write, 179 .endianness = DEVICE_LITTLE_ENDIAN, 180 }; 181 182 static void cmsdk_apb_timer_tick(void *opaque) 183 { 184 CMSDKAPBTIMER *s = CMSDK_APB_TIMER(opaque); 185 186 if (s->ctrl & R_CTRL_IRQEN_MASK) { 187 s->intstatus |= R_INTSTATUS_IRQ_MASK; 188 cmsdk_apb_timer_update(s); 189 } 190 } 191 192 static void cmsdk_apb_timer_reset(DeviceState *dev) 193 { 194 CMSDKAPBTIMER *s = CMSDK_APB_TIMER(dev); 195 196 trace_cmsdk_apb_timer_reset(); 197 s->ctrl = 0; 198 s->intstatus = 0; 199 ptimer_transaction_begin(s->timer); 200 ptimer_stop(s->timer); 201 /* Set the limit and the count */ 202 ptimer_set_limit(s->timer, 0, 1); 203 ptimer_transaction_commit(s->timer); 204 } 205 206 static void cmsdk_apb_timer_init(Object *obj) 207 { 208 SysBusDevice *sbd = SYS_BUS_DEVICE(obj); 209 CMSDKAPBTIMER *s = CMSDK_APB_TIMER(obj); 210 211 memory_region_init_io(&s->iomem, obj, &cmsdk_apb_timer_ops, 212 s, "cmsdk-apb-timer", 0x1000); 213 sysbus_init_mmio(sbd, &s->iomem); 214 sysbus_init_irq(sbd, &s->timerint); 215 } 216 217 static void cmsdk_apb_timer_realize(DeviceState *dev, Error **errp) 218 { 219 CMSDKAPBTIMER *s = CMSDK_APB_TIMER(dev); 220 221 if (s->pclk_frq == 0) { 222 error_setg(errp, "CMSDK APB timer: pclk-frq property must be set"); 223 return; 224 } 225 226 s->timer = ptimer_init(cmsdk_apb_timer_tick, s, 227 PTIMER_POLICY_WRAP_AFTER_ONE_PERIOD | 228 PTIMER_POLICY_TRIGGER_ONLY_ON_DECREMENT | 229 PTIMER_POLICY_NO_IMMEDIATE_RELOAD | 230 PTIMER_POLICY_NO_COUNTER_ROUND_DOWN); 231 232 ptimer_transaction_begin(s->timer); 233 ptimer_set_freq(s->timer, s->pclk_frq); 234 ptimer_transaction_commit(s->timer); 235 } 236 237 static const VMStateDescription cmsdk_apb_timer_vmstate = { 238 .name = "cmsdk-apb-timer", 239 .version_id = 1, 240 .minimum_version_id = 1, 241 .fields = (VMStateField[]) { 242 VMSTATE_PTIMER(timer, CMSDKAPBTIMER), 243 VMSTATE_UINT32(ctrl, CMSDKAPBTIMER), 244 VMSTATE_UINT32(value, CMSDKAPBTIMER), 245 VMSTATE_UINT32(reload, CMSDKAPBTIMER), 246 VMSTATE_UINT32(intstatus, CMSDKAPBTIMER), 247 VMSTATE_END_OF_LIST() 248 } 249 }; 250 251 static Property cmsdk_apb_timer_properties[] = { 252 DEFINE_PROP_UINT32("pclk-frq", CMSDKAPBTIMER, pclk_frq, 0), 253 DEFINE_PROP_END_OF_LIST(), 254 }; 255 256 static void cmsdk_apb_timer_class_init(ObjectClass *klass, void *data) 257 { 258 DeviceClass *dc = DEVICE_CLASS(klass); 259 260 dc->realize = cmsdk_apb_timer_realize; 261 dc->vmsd = &cmsdk_apb_timer_vmstate; 262 dc->reset = cmsdk_apb_timer_reset; 263 dc->props = cmsdk_apb_timer_properties; 264 } 265 266 static const TypeInfo cmsdk_apb_timer_info = { 267 .name = TYPE_CMSDK_APB_TIMER, 268 .parent = TYPE_SYS_BUS_DEVICE, 269 .instance_size = sizeof(CMSDKAPBTIMER), 270 .instance_init = cmsdk_apb_timer_init, 271 .class_init = cmsdk_apb_timer_class_init, 272 }; 273 274 static void cmsdk_apb_timer_register_types(void) 275 { 276 type_register_static(&cmsdk_apb_timer_info); 277 } 278 279 type_init(cmsdk_apb_timer_register_types); 280