diff options
Diffstat (limited to 'hw/misc/mps2-fpgaio.c')
| -rw-r--r-- | hw/misc/mps2-fpgaio.c | 146 |
1 files changed, 143 insertions, 3 deletions
diff --git a/hw/misc/mps2-fpgaio.c b/hw/misc/mps2-fpgaio.c index 7394a057d8..5cf10ebd66 100644 --- a/hw/misc/mps2-fpgaio.c +++ b/hw/misc/mps2-fpgaio.c @@ -22,6 +22,7 @@ #include "hw/sysbus.h" #include "hw/registerfields.h" #include "hw/misc/mps2-fpgaio.h" +#include "qemu/timer.h" REG32(LED0, 0) REG32(BUTTON, 8) @@ -32,10 +33,92 @@ 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: @@ -54,12 +137,20 @@ static uint64_t mps2_fpgaio_read(void *opaque, hwaddr offset, unsigned size) 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: - /* These are all upcounters of various frequencies. */ - qemu_log_mask(LOG_UNIMP, "MPS2 FPGAIO: counters unimplemented\n"); - r = 0; + resync_counter(s); + r = s->pscntr; break; default: qemu_log_mask(LOG_GUEST_ERROR, @@ -76,6 +167,7 @@ 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); @@ -89,6 +181,7 @@ static void mps2_fpgaio_write(void *opaque, hwaddr offset, uint64_t value, s->led0 = value & 0x3; break; case A_PRESCALE: + resync_counter(s); s->prescale = value; break; case A_MISC: @@ -100,6 +193,22 @@ static void mps2_fpgaio_write(void *opaque, hwaddr offset, uint64_t value, "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); @@ -116,11 +225,17 @@ static const MemoryRegionOps mps2_fpgaio_ops = { 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) @@ -133,6 +248,27 @@ static void mps2_fpgaio_init(Object *obj) 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, @@ -142,6 +278,10 @@ static const VMStateDescription mps2_fpgaio_vmstate = { VMSTATE_UINT32(prescale, MPS2FPGAIO), VMSTATE_UINT32(misc, MPS2FPGAIO), VMSTATE_END_OF_LIST() + }, + .subsections = (const VMStateDescription*[]) { + &mps2_fpgaio_counters_vmstate, + NULL } }; |