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openrisc-timer: Reduce overhead, Separate clock update functions

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The clock value is only evaluated when really necessary reducing
the overhead of the timer handling.

This also solves a problem in the way the Linux kernel
handles the timer and the expected accuracy.
The old version could lead to inaccurate timings.

Signed-off-by: Sebastian Macke <sebastian@macke.de>
Reviewed-by: Jia Liu <proljc@gmail.com>
Signed-off-by: Jia Liu <proljc@gmail.com>
This commit is contained in:
Sebastian Macke 2013-10-22 02:12:41 +02:00 • committed by Jia Liu
parent ae52bd96ce
commit d51552176a
3 changed files with 38 additions and 30 deletions
Download patch file Download diff file Expand all files Collapse all files

29
hw/openrisc/cputimer.c
View file

@ -30,19 +30,28 @@ static int is_counting;
void cpu_openrisc_count_update(OpenRISCCPU *cpu)
{
uint64_t now, next;
uint32_t wait;
uint64_t now;
now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
if (!is_counting) {
timer_del(cpu->env.timer);
last_clk = now;
return;
}
now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
cpu->env.ttcr += (uint32_t)muldiv64(now - last_clk, TIMER_FREQ,
get_ticks_per_sec());
last_clk = now;
}
void cpu_openrisc_timer_update(OpenRISCCPU *cpu)
{
uint32_t wait;
uint64_t now, next;
if (!is_counting) {
return;
}
cpu_openrisc_count_update(cpu);
now = last_clk;
if ((cpu->env.ttmr & TTMR_TP) <= (cpu->env.ttcr & TTMR_TP)) {
wait = TTMR_TP - (cpu->env.ttcr & TTMR_TP) + 1;
@ -50,7 +59,6 @@ void cpu_openrisc_count_update(OpenRISCCPU *cpu)
} else {
wait = (cpu->env.ttmr & TTMR_TP) - (cpu->env.ttcr & TTMR_TP);
}
next = now + muldiv64(wait, get_ticks_per_sec(), TIMER_FREQ);
timer_mod(cpu->env.timer, next);
}
@ -63,8 +71,9 @@ void cpu_openrisc_count_start(OpenRISCCPU *cpu)
void cpu_openrisc_count_stop(OpenRISCCPU *cpu)
{
is_counting = 0;
timer_del(cpu->env.timer);
cpu_openrisc_count_update(cpu);
is_counting = 0;
}
static void openrisc_timer_cb(void *opaque)
@ -84,15 +93,15 @@ static void openrisc_timer_cb(void *opaque)
break;
case TIMER_INTR:
cpu->env.ttcr = 0;
cpu_openrisc_count_start(cpu);
break;
case TIMER_SHOT:
cpu_openrisc_count_stop(cpu);
break;
case TIMER_CONT:
cpu_openrisc_count_start(cpu);
break;
}
cpu_openrisc_timer_update(cpu);
}
void cpu_openrisc_clock_init(OpenRISCCPU *cpu)