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openrisc-timer: Reduce overhead, Separate clock update functions 

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
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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)

1
target-openrisc/cpu.h
View File

@ -373,6 +373,7 @@ void cpu_openrisc_pic_init(OpenRISCCPU *cpu);
/* hw/openrisc_timer.c */
void cpu_openrisc_clock_init(OpenRISCCPU *cpu);
void cpu_openrisc_count_update(OpenRISCCPU *cpu);
void cpu_openrisc_timer_update(OpenRISCCPU *cpu);
void cpu_openrisc_count_start(OpenRISCCPU *cpu);
void cpu_openrisc_count_stop(OpenRISCCPU *cpu);

38
target-openrisc/sys_helper.c
View File

@ -127,33 +127,31 @@ void HELPER(mtspr)(CPUOpenRISCState *env,
break;
case TO_SPR(10, 0): /* TTMR */
{
if ((env->ttmr & TTMR_M) ^ (rb & TTMR_M)) {
switch (rb & TTMR_M) {
case TIMER_NONE:
cpu_openrisc_count_stop(cpu);
break;
case TIMER_INTR:
case TIMER_SHOT:
case TIMER_CONT:
cpu_openrisc_count_start(cpu);
break;
default:
break;
}
}
int ip = env->ttmr & TTMR_IP;
if (rb & TTMR_IP) { /* Keep IP bit. */
env->ttmr = (rb & ~TTMR_IP) + ip;
env->ttmr = (rb & ~TTMR_IP) | ip;
} else { /* Clear IP bit. */
env->ttmr = rb & ~TTMR_IP;
cs->interrupt_request &= ~CPU_INTERRUPT_TIMER;
}
cpu_openrisc_count_update(cpu);
switch (env->ttmr & TTMR_M) {
case TIMER_NONE:
cpu_openrisc_count_stop(cpu);
break;
case TIMER_INTR:
cpu_openrisc_count_start(cpu);
break;
case TIMER_SHOT:
cpu_openrisc_count_start(cpu);
break;
case TIMER_CONT:
cpu_openrisc_count_start(cpu);
break;
default:
break;
}
cpu_openrisc_timer_update(cpu);
}
break;
@ -162,7 +160,7 @@ void HELPER(mtspr)(CPUOpenRISCState *env,
if (env->ttmr & TIMER_NONE) {
return;
}
cpu_openrisc_count_start(cpu);
cpu_openrisc_timer_update(cpu);
break;
default: