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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

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: