hw/misc/mps2-fpgaio.c - qemu - Git at Google

 /*
  * ARM MPS2 AN505 FPGAIO emulation
  *
  * Copyright (c) 2018 Linaro Limited
  * Written by Peter Maydell
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License version 2 or
  *  (at your option) any later version.
  */

 /* This is a model of the "FPGA system control and I/O" block found
  * in the AN505 FPGA image for the MPS2 devboard.
  * It is documented in AN505:
  * http://infocenter.arm.com/help/topic/com.arm.doc.dai0505b/index.html
  */

 #include "qemu/osdep.h"
 #include "qemu/log.h"
 #include "qemu/module.h"
 #include "qapi/error.h"
 #include "trace.h"
 #include "hw/sysbus.h"
 #include "migration/vmstate.h"
 #include "hw/registerfields.h"
 #include "hw/misc/mps2-fpgaio.h"
 #include "hw/qdev-properties.h"
 #include "qemu/timer.h"

 REG32(LED0, 0)
 REG32(BUTTON, 8)
 REG32(CLK1HZ, 0x10)
 REG32(CLK100HZ, 0x14)
 REG32(COUNTER, 0x18)
 REG32(PRESCALE, 0x1c)
 REG32(PSCNTR, 0x20)
 REG32(MISC, 0x4c)

 static uint32_t counter_from_tickoff(int64_t now, int64_t tick_offset, int frq)
 {
     return muldiv64(now - tick_offset, frq, NANOSECONDS_PER_SECOND);
 }

 static int64_t tickoff_from_counter(int64_t now, uint32_t count, int frq)
 {
     return now - muldiv64(count, NANOSECONDS_PER_SECOND, frq);
 }

 static void resync_counter(MPS2FPGAIO *s)
 {
     /*
      * Update s->counter and s->pscntr to their true current values
      * by calculating how many times PSCNTR has ticked since the
      * last time we did a resync.
      */
     int64_t now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
     int64_t elapsed = now - s->pscntr_sync_ticks;

     /*
      * Round elapsed down to a whole number of PSCNTR ticks, so we don't
      * lose time if we do multiple resyncs in a single tick.
      */
     uint64_t ticks = muldiv64(elapsed, s->prescale_clk, NANOSECONDS_PER_SECOND);

     /*
      * Work out what PSCNTR and COUNTER have moved to. We assume that
      * PSCNTR reloads from PRESCALE one tick-period after it hits zero,
      * and that COUNTER increments at the same moment.
      */
     if (ticks == 0) {
         /* We haven't ticked since the last time we were asked */
         return;
     } else if (ticks < s->pscntr) {
         /* We haven't yet reached zero, just reduce the PSCNTR */
         s->pscntr -= ticks;
     } else {
         if (s->prescale == 0) {
             /*
              * If the reload value is zero then the PSCNTR will stick
              * at zero once it reaches it, and so we will increment
              * COUNTER every tick after that.
              */
             s->counter += ticks - s->pscntr;
             s->pscntr = 0;
         } else {
             /*
              * This is the complicated bit. This ASCII art diagram gives an
              * example with PRESCALE==5 PSCNTR==7:
              *
              * ticks  0  1  2  3  4  5  6  7  8  9 10 11 12 13 14
              * PSCNTR 7  6  5  4  3  2  1  0  5  4  3  2  1  0  5
              * cinc                           1                 2
              * y            0  1  2  3  4  5  6  7  8  9 10 11 12
              * x            0  1  2  3  4  5  0  1  2  3  4  5  0
              *
              * where x = y % (s->prescale + 1)
              * and so PSCNTR = s->prescale - x
              * and COUNTER is incremented by y / (s->prescale + 1)
              *
              * The case where PSCNTR < PRESCALE works out the same,
              * though we must be careful to calculate y as 64-bit unsigned
              * for all parts of the expression.
              * y < 0 is not possible because that implies ticks < s->pscntr.
              */
             uint64_t y = ticks - s->pscntr + s->prescale;
             s->pscntr = s->prescale - (y % (s->prescale + 1));
             s->counter += y / (s->prescale + 1);
         }
     }

     /*
      * Only advance the sync time to the timestamp of the last PSCNTR tick,
      * not all the way to 'now', so we don't lose time if we do multiple
      * resyncs in a single tick.
      */
     s->pscntr_sync_ticks += muldiv64(ticks, NANOSECONDS_PER_SECOND,
                                      s->prescale_clk);
 }

 static uint64_t mps2_fpgaio_read(void *opaque, hwaddr offset, unsigned size)
 {
     MPS2FPGAIO *s = MPS2_FPGAIO(opaque);
     uint64_t r;
     int64_t now;

     switch (offset) {
     case A_LED0:
         r = s->led0;
         break;
     case A_BUTTON:
         /* User-pressable board buttons. We don't model that, so just return
          * zeroes.
          */
         r = 0;
         break;
     case A_PRESCALE:
         r = s->prescale;
         break;
     case A_MISC:
         r = s->misc;
         break;
     case A_CLK1HZ:
         now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
         r = counter_from_tickoff(now, s->clk1hz_tick_offset, 1);
         break;
     case A_CLK100HZ:
         now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
         r = counter_from_tickoff(now, s->clk100hz_tick_offset, 100);
         break;
     case A_COUNTER:
         resync_counter(s);
         r = s->counter;
         break;
     case A_PSCNTR:
         resync_counter(s);
         r = s->pscntr;
         break;
     default:
         qemu_log_mask(LOG_GUEST_ERROR,
                       "MPS2 FPGAIO read: bad offset %x\n", (int) offset);
         r = 0;
         break;
     }

     trace_mps2_fpgaio_read(offset, r, size);
     return r;
 }

 static void mps2_fpgaio_write(void *opaque, hwaddr offset, uint64_t value,
                               unsigned size)
 {
     MPS2FPGAIO *s = MPS2_FPGAIO(opaque);
     int64_t now;

     trace_mps2_fpgaio_write(offset, value, size);

     switch (offset) {
     case A_LED0:
         /* LED bits [1:0] control board LEDs. We don't currently have
          * a mechanism for displaying this graphically, so use a trace event.
          */
         trace_mps2_fpgaio_leds(value & 0x02 ? '*' : '.',
                                value & 0x01 ? '*' : '.');
         s->led0 = value & 0x3;
         break;
     case A_PRESCALE:
         resync_counter(s);
         s->prescale = value;
         break;
     case A_MISC:
         /* These are control bits for some of the other devices on the
          * board (SPI, CLCD, etc). We don't implement that yet, so just
          * make the bits read as written.
          */
         qemu_log_mask(LOG_UNIMP,
                       "MPS2 FPGAIO: MISC control bits unimplemented\n");
         s->misc = value;
         break;
     case A_CLK1HZ:
         now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
         s->clk1hz_tick_offset = tickoff_from_counter(now, value, 1);
         break;
     case A_CLK100HZ:
         now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
         s->clk100hz_tick_offset = tickoff_from_counter(now, value, 100);
         break;
     case A_COUNTER:
         resync_counter(s);
         s->counter = value;
         break;
     case A_PSCNTR:
         resync_counter(s);
         s->pscntr = value;
         break;
     default:
         qemu_log_mask(LOG_GUEST_ERROR,
                       "MPS2 FPGAIO write: bad offset 0x%x\n", (int) offset);
         break;
     }
 }

 static const MemoryRegionOps mps2_fpgaio_ops = {
     .read = mps2_fpgaio_read,
     .write = mps2_fpgaio_write,
     .endianness = DEVICE_LITTLE_ENDIAN,
 };

 static void mps2_fpgaio_reset(DeviceState *dev)
 {
     MPS2FPGAIO *s = MPS2_FPGAIO(dev);
     int64_t now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);

     trace_mps2_fpgaio_reset();
     s->led0 = 0;
     s->prescale = 0;
     s->misc = 0;
     s->clk1hz_tick_offset = tickoff_from_counter(now, 0, 1);
     s->clk100hz_tick_offset = tickoff_from_counter(now, 0, 100);
     s->counter = 0;
     s->pscntr = 0;
     s->pscntr_sync_ticks = now;
 }

 static void mps2_fpgaio_init(Object *obj)
 {
     SysBusDevice *sbd = SYS_BUS_DEVICE(obj);
     MPS2FPGAIO *s = MPS2_FPGAIO(obj);

     memory_region_init_io(&s->iomem, obj, &mps2_fpgaio_ops, s,
                           "mps2-fpgaio", 0x1000);
     sysbus_init_mmio(sbd, &s->iomem);
 }

 static bool mps2_fpgaio_counters_needed(void *opaque)
 {
     /* Currently vmstate.c insists all subsections have a 'needed' function */
     return true;
 }

 static const VMStateDescription mps2_fpgaio_counters_vmstate = {
     .name = "mps2-fpgaio/counters",
     .version_id = 2,
     .minimum_version_id = 2,
     .needed = mps2_fpgaio_counters_needed,
     .fields = (VMStateField[]) {
         VMSTATE_INT64(clk1hz_tick_offset, MPS2FPGAIO),
         VMSTATE_INT64(clk100hz_tick_offset, MPS2FPGAIO),
         VMSTATE_UINT32(counter, MPS2FPGAIO),
         VMSTATE_UINT32(pscntr, MPS2FPGAIO),
         VMSTATE_INT64(pscntr_sync_ticks, MPS2FPGAIO),
         VMSTATE_END_OF_LIST()
     }
 };

 static const VMStateDescription mps2_fpgaio_vmstate = {
     .name = "mps2-fpgaio",
     .version_id = 1,
     .minimum_version_id = 1,
     .fields = (VMStateField[]) {
         VMSTATE_UINT32(led0, MPS2FPGAIO),
         VMSTATE_UINT32(prescale, MPS2FPGAIO),
         VMSTATE_UINT32(misc, MPS2FPGAIO),
         VMSTATE_END_OF_LIST()
     },
     .subsections = (const VMStateDescription*[]) {
         &mps2_fpgaio_counters_vmstate,
         NULL
     }
 };

 static Property mps2_fpgaio_properties[] = {
     /* Frequency of the prescale counter */
     DEFINE_PROP_UINT32("prescale-clk", MPS2FPGAIO, prescale_clk, 20000000),
     DEFINE_PROP_END_OF_LIST(),
 };

 static void mps2_fpgaio_class_init(ObjectClass *klass, void *data)
 {
     DeviceClass *dc = DEVICE_CLASS(klass);

     dc->vmsd = &mps2_fpgaio_vmstate;
     dc->reset = mps2_fpgaio_reset;
     dc->props = mps2_fpgaio_properties;
 }

 static const TypeInfo mps2_fpgaio_info = {
     .name = TYPE_MPS2_FPGAIO,
     .parent = TYPE_SYS_BUS_DEVICE,
     .instance_size = sizeof(MPS2FPGAIO),
     .instance_init = mps2_fpgaio_init,
     .class_init = mps2_fpgaio_class_init,
 };

 static void mps2_fpgaio_register_types(void)
 {
     type_register_static(&mps2_fpgaio_info);
 }

 type_init(mps2_fpgaio_register_types);
	/*
	* ARM MPS2 AN505 FPGAIO emulation
	*
	* Copyright (c) 2018 Linaro Limited
	* Written by Peter Maydell
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License version 2 or
	* (at your option) any later version.
	*/

	/* This is a model of the "FPGA system control and I/O" block found
	* in the AN505 FPGA image for the MPS2 devboard.
	* It is documented in AN505:
	* http://infocenter.arm.com/help/topic/com.arm.doc.dai0505b/index.html
	*/

	#include "qemu/osdep.h"
	#include "qemu/log.h"
	#include "qemu/module.h"
	#include "qapi/error.h"
	#include "trace.h"
	#include "hw/sysbus.h"
	#include "migration/vmstate.h"
	#include "hw/registerfields.h"
	#include "hw/misc/mps2-fpgaio.h"
	#include "hw/qdev-properties.h"
	#include "qemu/timer.h"

	REG32(LED0, 0)
	REG32(BUTTON, 8)
	REG32(CLK1HZ, 0x10)
	REG32(CLK100HZ, 0x14)
	REG32(COUNTER, 0x18)
	REG32(PRESCALE, 0x1c)
	REG32(PSCNTR, 0x20)
	REG32(MISC, 0x4c)

	static uint32_t counter_from_tickoff(int64_t now, int64_t tick_offset, int frq)
	{
	return muldiv64(now - tick_offset, frq, NANOSECONDS_PER_SECOND);
	}

	static int64_t tickoff_from_counter(int64_t now, uint32_t count, int frq)
	{
	return now - muldiv64(count, NANOSECONDS_PER_SECOND, frq);
	}

	static void resync_counter(MPS2FPGAIO *s)
	{
	/*
	* Update s->counter and s->pscntr to their true current values
	* by calculating how many times PSCNTR has ticked since the
	* last time we did a resync.
	*/
	int64_t now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
	int64_t elapsed = now - s->pscntr_sync_ticks;

	/*
	* Round elapsed down to a whole number of PSCNTR ticks, so we don't
	* lose time if we do multiple resyncs in a single tick.
	*/
	uint64_t ticks = muldiv64(elapsed, s->prescale_clk, NANOSECONDS_PER_SECOND);

	/*
	* Work out what PSCNTR and COUNTER have moved to. We assume that
	* PSCNTR reloads from PRESCALE one tick-period after it hits zero,
	* and that COUNTER increments at the same moment.
	*/
	if (ticks == 0) {
	/* We haven't ticked since the last time we were asked */
	return;
	} else if (ticks < s->pscntr) {
	/* We haven't yet reached zero, just reduce the PSCNTR */
	s->pscntr -= ticks;
	} else {
	if (s->prescale == 0) {
	/*
	* If the reload value is zero then the PSCNTR will stick
	* at zero once it reaches it, and so we will increment
	* COUNTER every tick after that.
	*/
	s->counter += ticks - s->pscntr;
	s->pscntr = 0;
	} else {
	/*
	* This is the complicated bit. This ASCII art diagram gives an
	* example with PRESCALE==5 PSCNTR==7:
	*
	* ticks 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
	* PSCNTR 7 6 5 4 3 2 1 0 5 4 3 2 1 0 5
	* cinc 1 2
	* y 0 1 2 3 4 5 6 7 8 9 10 11 12
	* x 0 1 2 3 4 5 0 1 2 3 4 5 0
	*
	* where x = y % (s->prescale + 1)
	* and so PSCNTR = s->prescale - x
	* and COUNTER is incremented by y / (s->prescale + 1)
	*
	* The case where PSCNTR < PRESCALE works out the same,
	* though we must be careful to calculate y as 64-bit unsigned
	* for all parts of the expression.
	* y < 0 is not possible because that implies ticks < s->pscntr.
	*/
	uint64_t y = ticks - s->pscntr + s->prescale;
	s->pscntr = s->prescale - (y % (s->prescale + 1));
	s->counter += y / (s->prescale + 1);
	}
	}

	/*
	* Only advance the sync time to the timestamp of the last PSCNTR tick,
	* not all the way to 'now', so we don't lose time if we do multiple
	* resyncs in a single tick.
	*/
	s->pscntr_sync_ticks += muldiv64(ticks, NANOSECONDS_PER_SECOND,
	s->prescale_clk);
	}

	static uint64_t mps2_fpgaio_read(void *opaque, hwaddr offset, unsigned size)
	{
	MPS2FPGAIO *s = MPS2_FPGAIO(opaque);
	uint64_t r;
	int64_t now;

	switch (offset) {
	case A_LED0:
	r = s->led0;
	break;
	case A_BUTTON:
	/* User-pressable board buttons. We don't model that, so just return
	* zeroes.
	*/
	r = 0;
	break;
	case A_PRESCALE:
	r = s->prescale;
	break;
	case A_MISC:
	r = s->misc;
	break;
	case A_CLK1HZ:
	now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
	r = counter_from_tickoff(now, s->clk1hz_tick_offset, 1);
	break;
	case A_CLK100HZ:
	now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
	r = counter_from_tickoff(now, s->clk100hz_tick_offset, 100);
	break;
	case A_COUNTER:
	resync_counter(s);
	r = s->counter;
	break;
	case A_PSCNTR:
	resync_counter(s);
	r = s->pscntr;
	break;
	default:
	qemu_log_mask(LOG_GUEST_ERROR,
	"MPS2 FPGAIO read: bad offset %x\n", (int) offset);
	r = 0;
	break;
	}

	trace_mps2_fpgaio_read(offset, r, size);
	return r;
	}

	static void mps2_fpgaio_write(void *opaque, hwaddr offset, uint64_t value,
	unsigned size)
	{
	MPS2FPGAIO *s = MPS2_FPGAIO(opaque);
	int64_t now;

	trace_mps2_fpgaio_write(offset, value, size);

	switch (offset) {
	case A_LED0:
	/* LED bits [1:0] control board LEDs. We don't currently have
	* a mechanism for displaying this graphically, so use a trace event.
	*/
	trace_mps2_fpgaio_leds(value & 0x02 ? '*' : '.',
	value & 0x01 ? '*' : '.');
	s->led0 = value & 0x3;
	break;
	case A_PRESCALE:
	resync_counter(s);
	s->prescale = value;
	break;
	case A_MISC:
	/* These are control bits for some of the other devices on the
	* board (SPI, CLCD, etc). We don't implement that yet, so just
	* make the bits read as written.
	*/
	qemu_log_mask(LOG_UNIMP,
	"MPS2 FPGAIO: MISC control bits unimplemented\n");
	s->misc = value;
	break;
	case A_CLK1HZ:
	now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
	s->clk1hz_tick_offset = tickoff_from_counter(now, value, 1);
	break;
	case A_CLK100HZ:
	now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
	s->clk100hz_tick_offset = tickoff_from_counter(now, value, 100);
	break;
	case A_COUNTER:
	resync_counter(s);
	s->counter = value;
	break;
	case A_PSCNTR:
	resync_counter(s);
	s->pscntr = value;
	break;
	default:
	qemu_log_mask(LOG_GUEST_ERROR,
	"MPS2 FPGAIO write: bad offset 0x%x\n", (int) offset);
	break;
	}
	}

	static const MemoryRegionOps mps2_fpgaio_ops = {
	.read = mps2_fpgaio_read,
	.write = mps2_fpgaio_write,
	.endianness = DEVICE_LITTLE_ENDIAN,
	};

	static void mps2_fpgaio_reset(DeviceState *dev)
	{
	MPS2FPGAIO *s = MPS2_FPGAIO(dev);
	int64_t now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);

	trace_mps2_fpgaio_reset();
	s->led0 = 0;
	s->prescale = 0;
	s->misc = 0;
	s->clk1hz_tick_offset = tickoff_from_counter(now, 0, 1);
	s->clk100hz_tick_offset = tickoff_from_counter(now, 0, 100);
	s->counter = 0;
	s->pscntr = 0;
	s->pscntr_sync_ticks = now;
	}

	static void mps2_fpgaio_init(Object *obj)
	{
	SysBusDevice *sbd = SYS_BUS_DEVICE(obj);
	MPS2FPGAIO *s = MPS2_FPGAIO(obj);

	memory_region_init_io(&s->iomem, obj, &mps2_fpgaio_ops, s,
	"mps2-fpgaio", 0x1000);
	sysbus_init_mmio(sbd, &s->iomem);
	}

	static bool mps2_fpgaio_counters_needed(void *opaque)
	{
	/* Currently vmstate.c insists all subsections have a 'needed' function */
	return true;
	}

	static const VMStateDescription mps2_fpgaio_counters_vmstate = {
	.name = "mps2-fpgaio/counters",
	.version_id = 2,
	.minimum_version_id = 2,
	.needed = mps2_fpgaio_counters_needed,
	.fields = (VMStateField[]) {
	VMSTATE_INT64(clk1hz_tick_offset, MPS2FPGAIO),
	VMSTATE_INT64(clk100hz_tick_offset, MPS2FPGAIO),
	VMSTATE_UINT32(counter, MPS2FPGAIO),
	VMSTATE_UINT32(pscntr, MPS2FPGAIO),
	VMSTATE_INT64(pscntr_sync_ticks, MPS2FPGAIO),
	VMSTATE_END_OF_LIST()
	}
	};

	static const VMStateDescription mps2_fpgaio_vmstate = {
	.name = "mps2-fpgaio",
	.version_id = 1,
	.minimum_version_id = 1,
	.fields = (VMStateField[]) {
	VMSTATE_UINT32(led0, MPS2FPGAIO),
	VMSTATE_UINT32(prescale, MPS2FPGAIO),
	VMSTATE_UINT32(misc, MPS2FPGAIO),
	VMSTATE_END_OF_LIST()
	},
	.subsections = (const VMStateDescription*[]) {
	&mps2_fpgaio_counters_vmstate,
	NULL
	}
	};

	static Property mps2_fpgaio_properties[] = {
	/* Frequency of the prescale counter */
	DEFINE_PROP_UINT32("prescale-clk", MPS2FPGAIO, prescale_clk, 20000000),
	DEFINE_PROP_END_OF_LIST(),
	};

	static void mps2_fpgaio_class_init(ObjectClass klass, void data)
	{
	DeviceClass *dc = DEVICE_CLASS(klass);

	dc->vmsd = &mps2_fpgaio_vmstate;
	dc->reset = mps2_fpgaio_reset;
	dc->props = mps2_fpgaio_properties;
	}

	static const TypeInfo mps2_fpgaio_info = {
	.name = TYPE_MPS2_FPGAIO,
	.parent = TYPE_SYS_BUS_DEVICE,
	.instance_size = sizeof(MPS2FPGAIO),
	.instance_init = mps2_fpgaio_init,
	.class_init = mps2_fpgaio_class_init,
	};

	static void mps2_fpgaio_register_types(void)
	{
	type_register_static(&mps2_fpgaio_info);
	}

	type_init(mps2_fpgaio_register_types);