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); 320