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[Qemu-devel] [PATCH v2 1/7] PCI: remove muldiv64()
From: |
Laurent Vivier |
Subject: |
[Qemu-devel] [PATCH v2 1/7] PCI: remove muldiv64() |
Date: |
Wed, 26 Aug 2015 20:05:32 +0200 |
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 <address@hidden>
---
hw/net/pcnet.c | 3 +--
hw/net/rtl8139.c | 14 ++++++--------
hw/watchdog/wdt_i6300esb.c | 11 +++--------
tests/rtl8139-test.c | 2 +-
4 files changed, 11 insertions(+), 19 deletions(-)
diff --git a/hw/net/pcnet.c b/hw/net/pcnet.c
index 3437376..0eb3cc4 100644
--- a/hw/net/pcnet.c
+++ b/hw/net/pcnet.c
@@ -670,8 +670,7 @@ static inline hwaddr pcnet_rdra_addr(PCNetState *s, int idx)
static inline int64_t pcnet_get_next_poll_time(PCNetState *s, int64_t
current_time)
{
int64_t next_time = current_time +
- muldiv64(65536 - (CSR_SPND(s) ? 0 : CSR_POLL(s)),
- get_ticks_per_sec(), 33000000L);
+ (65536 - (CSR_SPND(s) ? 0 : CSR_POLL(s))) * 30;
if (next_time <= current_time)
next_time = current_time + 1;
return next_time;
diff --git a/hw/net/rtl8139.c b/hw/net/rtl8139.c
index edbb61c..1e119e6 100644
--- a/hw/net/rtl8139.c
+++ b/hw/net/rtl8139.c
@@ -63,7 +63,7 @@
/* 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) ) )
@@ -2881,8 +2881,7 @@ 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");
@@ -2900,7 +2899,7 @@ 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;
}
@@ -3174,8 +3173,8 @@ 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;
@@ -3269,8 +3268,7 @@ 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;
}
diff --git a/hw/watchdog/wdt_i6300esb.c b/hw/watchdog/wdt_i6300esb.c
index cfa2b1b..a91c8fd 100644
--- a/hw/watchdog/wdt_i6300esb.c
+++ b/hw/watchdog/wdt_i6300esb.c
@@ -129,14 +129,9 @@ static void i6300esb_restart_timer(I6300State *d, int
stage)
else
timeout <<= 5;
- /* Get the timeout in units of ticks_per_sec.
- *
- * ticks_per_sec is typically 10^9 == 0x3B9ACA00 (30 bits), with
- * 20 bits of user supplied preload, and 15 bits of scale, the
- * multiply here can exceed 64-bits, before we divide by 33MHz, so
- * we use a higher-precision intermediate result.
- */
- timeout = muldiv64(get_ticks_per_sec(), timeout, 33000000);
+ /* Get the timeout in nanoseconds. */
+
+ timeout = timeout * 30; /* on a PCI bus, 1 tick is 30 ns*/
i6300esb_debug("stage %d, timeout %" PRIi64 "\n", d->stage, timeout);
diff --git a/tests/rtl8139-test.c b/tests/rtl8139-test.c
index e749be3..ba62851 100644
--- a/tests/rtl8139-test.c
+++ b/tests/rtl8139-test.c
@@ -20,7 +20,7 @@ static void nop(void)
{
}
-#define CLK 33000000
+#define CLK 33333333
static QPCIBus *pcibus;
static QPCIDevice *dev;
--
2.1.0
- [Qemu-devel] [PATCH v2 0/7] remove useless muldiv64(), Laurent Vivier, 2015/08/26
- [Qemu-devel] [PATCH v2 1/7] PCI: remove muldiv64(),
Laurent Vivier <=
- [Qemu-devel] [PATCH v2 3/7] openrisc: remove muldiv64(), Laurent Vivier, 2015/08/26
- [Qemu-devel] [PATCH v2 2/7] mips: remove muldiv64(), Laurent Vivier, 2015/08/26
- [Qemu-devel] [PATCH v2 5/7] hpet: remove muldiv64(), Laurent Vivier, 2015/08/26
- [Qemu-devel] [PATCH v2 4/7] arm: clarify the use of muldiv64(), Laurent Vivier, 2015/08/26
- [Qemu-devel] [PATCH v2 7/7] net: remove muldiv64(), Laurent Vivier, 2015/08/26
- [Qemu-devel] [PATCH v2 6/7] bt: remove muldiv64(), Laurent Vivier, 2015/08/26