david.venhoff/QEMU-Nyx-fork
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

mips: remove muldiv64()

Browse Source 
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 <lvivier@redhat.com>
Reviewed-by: Leon Alrae <leon.alrae@imgtec.com>
This commit is contained in:
Laurent Vivier 2015-08-25 16:16:21 +02:00
parent c6acbe861f
commit 683dca6bd5
1 changed files with 8 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

19
hw/mips/cputimer.c
View File

@ -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)
@ -57,9 +57,8 @@ 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);
}
@ -87,8 +86,7 @@ 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);
}
}
@ -103,9 +101,8 @@ 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);
}
@ -129,8 +126,8 @@ 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)