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/qdev-clock.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 ptimer_transaction_begin(s->timer); 125 if (s->ctrl & R_CTRL_EN_MASK) { 126 ptimer_run(s->timer, ptimer_get_limit(s->timer) == 0); 127 } else { 128 ptimer_stop(s->timer); 129 } 130 ptimer_transaction_commit(s->timer); 131 break; 132 case A_RELOAD: 133 /* Writing to reload also sets the current timer value */ 134 ptimer_transaction_begin(s->timer); 135 if (!value) { 136 ptimer_stop(s->timer); 137 } 138 ptimer_set_limit(s->timer, value, 1); 139 if (value && (s->ctrl & R_CTRL_EN_MASK)) { 140 /* 141 * Make sure timer is running (it might have stopped if this 142 * was an expired one-shot timer) 143 */ 144 ptimer_run(s->timer, 0); 145 } 146 ptimer_transaction_commit(s->timer); 147 break; 148 case A_VALUE: 149 ptimer_transaction_begin(s->timer); 150 if (!value && !ptimer_get_limit(s->timer)) { 151 ptimer_stop(s->timer); 152 } 153 ptimer_set_count(s->timer, value); 154 if (value && (s->ctrl & R_CTRL_EN_MASK)) { 155 ptimer_run(s->timer, ptimer_get_limit(s->timer) == 0); 156 } 157 ptimer_transaction_commit(s->timer); 158 break; 159 case A_INTSTATUS: 160 /* Just one bit, which is W1C. */ 161 value &= 1; 162 s->intstatus &= ~value; 163 cmsdk_apb_timer_update(s); 164 break; 165 case A_PID4 ... A_CID3: 166 qemu_log_mask(LOG_GUEST_ERROR, 167 "CMSDK APB timer write: write to RO offset 0x%x\n", 168 (int)offset); 169 break; 170 default: 171 qemu_log_mask(LOG_GUEST_ERROR, 172 "CMSDK APB timer write: bad offset 0x%x\n", (int) offset); 173 break; 174 } 175 } 176 177 static const MemoryRegionOps cmsdk_apb_timer_ops = { 178 .read = cmsdk_apb_timer_read, 179 .write = cmsdk_apb_timer_write, 180 .endianness = DEVICE_LITTLE_ENDIAN, 181 }; 182 183 static void cmsdk_apb_timer_tick(void *opaque) 184 { 185 CMSDKAPBTimer *s = CMSDK_APB_TIMER(opaque); 186 187 if (s->ctrl & R_CTRL_IRQEN_MASK) { 188 s->intstatus |= R_INTSTATUS_IRQ_MASK; 189 cmsdk_apb_timer_update(s); 190 } 191 } 192 193 static void cmsdk_apb_timer_reset(DeviceState *dev) 194 { 195 CMSDKAPBTimer *s = CMSDK_APB_TIMER(dev); 196 197 trace_cmsdk_apb_timer_reset(); 198 s->ctrl = 0; 199 s->intstatus = 0; 200 ptimer_transaction_begin(s->timer); 201 ptimer_stop(s->timer); 202 /* Set the limit and the count */ 203 ptimer_set_limit(s->timer, 0, 1); 204 ptimer_transaction_commit(s->timer); 205 } 206 207 static void cmsdk_apb_timer_clk_update(void *opaque, ClockEvent event) 208 { 209 CMSDKAPBTimer *s = CMSDK_APB_TIMER(opaque); 210 211 ptimer_transaction_begin(s->timer); 212 ptimer_set_period_from_clock(s->timer, s->pclk, 1); 213 ptimer_transaction_commit(s->timer); 214 } 215 216 static void cmsdk_apb_timer_init(Object *obj) 217 { 218 SysBusDevice *sbd = SYS_BUS_DEVICE(obj); 219 CMSDKAPBTimer *s = CMSDK_APB_TIMER(obj); 220 221 memory_region_init_io(&s->iomem, obj, &cmsdk_apb_timer_ops, 222 s, "cmsdk-apb-timer", 0x1000); 223 sysbus_init_mmio(sbd, &s->iomem); 224 sysbus_init_irq(sbd, &s->timerint); 225 s->pclk = qdev_init_clock_in(DEVICE(s), "pclk", 226 cmsdk_apb_timer_clk_update, s, ClockUpdate); 227 } 228 229 static void cmsdk_apb_timer_realize(DeviceState *dev, Error **errp) 230 { 231 CMSDKAPBTimer *s = CMSDK_APB_TIMER(dev); 232 233 if (!clock_has_source(s->pclk)) { 234 error_setg(errp, "CMSDK APB timer: pclk clock must be connected"); 235 return; 236 } 237 238 s->timer = ptimer_init(cmsdk_apb_timer_tick, s, 239 PTIMER_POLICY_WRAP_AFTER_ONE_PERIOD | 240 PTIMER_POLICY_TRIGGER_ONLY_ON_DECREMENT | 241 PTIMER_POLICY_NO_IMMEDIATE_RELOAD | 242 PTIMER_POLICY_NO_COUNTER_ROUND_DOWN); 243 244 ptimer_transaction_begin(s->timer); 245 ptimer_set_period_from_clock(s->timer, s->pclk, 1); 246 ptimer_transaction_commit(s->timer); 247 } 248 249 static const VMStateDescription cmsdk_apb_timer_vmstate = { 250 .name = "cmsdk-apb-timer", 251 .version_id = 2, 252 .minimum_version_id = 2, 253 .fields = (const VMStateField[]) { 254 VMSTATE_PTIMER(timer, CMSDKAPBTimer), 255 VMSTATE_CLOCK(pclk, CMSDKAPBTimer), 256 VMSTATE_UINT32(ctrl, CMSDKAPBTimer), 257 VMSTATE_UINT32(value, CMSDKAPBTimer), 258 VMSTATE_UINT32(reload, CMSDKAPBTimer), 259 VMSTATE_UINT32(intstatus, CMSDKAPBTimer), 260 VMSTATE_END_OF_LIST() 261 } 262 }; 263 264 static void cmsdk_apb_timer_class_init(ObjectClass *klass, void *data) 265 { 266 DeviceClass *dc = DEVICE_CLASS(klass); 267 268 dc->realize = cmsdk_apb_timer_realize; 269 dc->vmsd = &cmsdk_apb_timer_vmstate; 270 dc->reset = cmsdk_apb_timer_reset; 271 } 272 273 static const TypeInfo cmsdk_apb_timer_info = { 274 .name = TYPE_CMSDK_APB_TIMER, 275 .parent = TYPE_SYS_BUS_DEVICE, 276 .instance_size = sizeof(CMSDKAPBTimer), 277 .instance_init = cmsdk_apb_timer_init, 278 .class_init = cmsdk_apb_timer_class_init, 279 }; 280 281 static void cmsdk_apb_timer_register_types(void) 282 { 283 type_register_static(&cmsdk_apb_timer_info); 284 } 285 286 type_init(cmsdk_apb_timer_register_types); 287