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rtl8139: remove muldiv64()

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Originally, timers were ticks based, and it made sense to
add ticks to current time to know when to trigger an alarm.

But since commit:

7447545 change all other clock references to use nanosecond resolution accessors

All timers use nanoseconds and we need to convert ticks to nanoseconds, by
doing something like:

    y = muldiv64(x, get_ticks_per_sec(), PCI_FREQUENCY)

where x is the number of device ticks and y the number of system ticks.

y is used as nanoseconds in timer functions,
it works because 1 tick is 1 nanosecond.
(get_ticks_per_sec() is 10^9)

But as PCI frequency is 33 MHz, we can also do:

    y = x * 30; /* 33 MHz PCI period is 30 ns */

Which is much more simple.

This implies a 33.333333 MHz PCI frequency,
but this is correct.

Signed-off-by: Laurent Vivier <lvivier@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Laurent Vivier 2015-08-24 19:29:45 +02:00
parent 9491e9bc01
commit 37b9ab92f7
2 changed files with 7 additions and 9 deletions
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14
hw/net/rtl8139.c
View File

@ -64,7 +64,7 @@
/* debug RTL8139 card */
//#define DEBUG_RTL8139 1
#define PCI_FREQUENCY 33000000L
#define PCI_PERIOD 30 /* 30 ns period = 33.333333 Mhz frequency */
#define SET_MASKED(input, mask, curr) \
( ( (input) & ~(mask) ) | ( (curr) & (mask) ) )
@ -2834,8 +2834,7 @@ static void rtl8139_io_writew(void *opaque, uint8_t addr, uint32_t val)
static void rtl8139_set_next_tctr_time(RTL8139State *s)
{
const uint64_t ns_per_period =
muldiv64(0x100000000LL, get_ticks_per_sec(), PCI_FREQUENCY);
const uint64_t ns_per_period = (uint64_t)PCI_PERIOD << 32;
DPRINTF("entered rtl8139_set_next_tctr_time\n");
@ -2853,7 +2852,7 @@ static void rtl8139_set_next_tctr_time(RTL8139State *s)
if (!s->TimerInt) {
timer_del(s->timer);
} else {
uint64_t delta = muldiv64(s->TimerInt, get_ticks_per_sec(), PCI_FREQUENCY);
uint64_t delta = (uint64_t)s->TimerInt * PCI_PERIOD;
if (s->TCTR_base + delta <= qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL)) {
delta += ns_per_period;
}
@ -3127,8 +3126,8 @@ static uint32_t rtl8139_io_readl(void *opaque, uint8_t addr)
break;
case Timer:
ret = muldiv64(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) - s->TCTR_base,
PCI_FREQUENCY, get_ticks_per_sec());
ret = (qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) - s->TCTR_base) /
PCI_PERIOD;
DPRINTF("TCTR Timer read val=0x%08x\n", ret);
break;
@ -3222,8 +3221,7 @@ static void rtl8139_pre_save(void *opaque)
int64_t current_time = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
/* for migration to older versions */
s->TCTR = muldiv64(current_time - s->TCTR_base, PCI_FREQUENCY,
get_ticks_per_sec());
s->TCTR = (current_time - s->TCTR_base) / PCI_PERIOD;
s->rtl8139_mmio_io_addr_dummy = 0;
}

2
tests/rtl8139-test.c
View File

@ -20,7 +20,7 @@ static void nop(void)
{
}
#define CLK 33000000
#define CLK 33333333
static QPCIBus *pcibus;
static QPCIDevice *dev;