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[Qemu-trivial] [PATCH v2 2/7] mips: remove muldiv64()
From: |
Laurent Vivier |
Subject: |
[Qemu-trivial] [PATCH v2 2/7] mips: remove muldiv64() |
Date: |
Wed, 26 Aug 2015 20:05:33 +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(), TIMER_FREQ)
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 MIPS timer frequency is 100 MHz, we can also do:
y = x * 10; /* 100 MHz period is 10 ns */
Signed-off-by: Laurent Vivier <address@hidden>
---
hw/mips/cputimer.c | 19 ++++++++-----------
1 file changed, 8 insertions(+), 11 deletions(-)
diff --git a/hw/mips/cputimer.c b/hw/mips/cputimer.c
index 577c9ae..a74ae5c 100644
--- a/hw/mips/cputimer.c
+++ b/hw/mips/cputimer.c
@@ -25,7 +25,7 @@
#include "qemu/timer.h"
#include "sysemu/kvm.h"
-#define TIMER_FREQ 100 * 1000 * 1000
+#define TIMER_PERIOD 10 /* 10 ns period for 100 Mhz frequency */
/* XXX: do not use a global */
uint32_t cpu_mips_get_random (CPUMIPSState *env)
@@ -49,9 +49,8 @@ static void cpu_mips_timer_update(CPUMIPSState *env)
uint32_t wait;
now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
- wait = env->CP0_Compare - env->CP0_Count -
- (uint32_t)muldiv64(now, TIMER_FREQ, get_ticks_per_sec());
- next = now + muldiv64(wait, get_ticks_per_sec(), TIMER_FREQ);
+ wait = env->CP0_Compare - env->CP0_Count - (uint32_t)(now / TIMER_PERIOD);
+ next = now + (uint64_t)wait * TIMER_PERIOD;
timer_mod(env->timer, next);
}
@@ -79,8 +78,7 @@ uint32_t cpu_mips_get_count (CPUMIPSState *env)
cpu_mips_timer_expire(env);
}
- return env->CP0_Count +
- (uint32_t)muldiv64(now, TIMER_FREQ, get_ticks_per_sec());
+ return env->CP0_Count + (uint32_t)(now / TIMER_PERIOD);
}
}
@@ -95,9 +93,8 @@ void cpu_mips_store_count (CPUMIPSState *env, uint32_t count)
env->CP0_Count = count;
else {
/* Store new count register */
- env->CP0_Count =
- count - (uint32_t)muldiv64(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL),
- TIMER_FREQ, get_ticks_per_sec());
+ env->CP0_Count = count -
+ (uint32_t)(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) /
TIMER_PERIOD);
/* Update timer timer */
cpu_mips_timer_update(env);
}
@@ -121,8 +118,8 @@ void cpu_mips_start_count(CPUMIPSState *env)
void cpu_mips_stop_count(CPUMIPSState *env)
{
/* Store the current value */
- env->CP0_Count += (uint32_t)muldiv64(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL),
- TIMER_FREQ, get_ticks_per_sec());
+ env->CP0_Count += (uint32_t)(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) /
+ TIMER_PERIOD);
}
static void mips_timer_cb (void *opaque)
--
2.1.0
- [Qemu-trivial] [PATCH v2 0/7] remove useless muldiv64(), Laurent Vivier, 2015/08/26
- [Qemu-trivial] [PATCH v2 1/7] PCI: remove muldiv64(), Laurent Vivier, 2015/08/26
- [Qemu-trivial] [PATCH v2 3/7] openrisc: remove muldiv64(), Laurent Vivier, 2015/08/26
- [Qemu-trivial] [PATCH v2 2/7] mips: remove muldiv64(),
Laurent Vivier <=
- [Qemu-trivial] [PATCH v2 5/7] hpet: remove muldiv64(), Laurent Vivier, 2015/08/26
- [Qemu-trivial] [PATCH v2 4/7] arm: clarify the use of muldiv64(), Laurent Vivier, 2015/08/26
- [Qemu-trivial] [PATCH v2 7/7] net: remove muldiv64(), Laurent Vivier, 2015/08/26
- [Qemu-trivial] [PATCH v2 6/7] bt: remove muldiv64(), Laurent Vivier, 2015/08/26