From: Sebastian Macke <sebastian@macke.de>
To: qemu-devel@nongnu.org, Jia Liu <proljc@gmail.com>
Cc: openrisc <openrisc@lists.openrisc.net>,
"openrisc@lists.opencores.org" <openrisc@lists.opencores.org>
Subject: [Qemu-devel] [PATCH] openrisc-timer: Reduce overhead, Separate clock update functions
Date: Sat, 19 Oct 2013 14:36:06 -0700 [thread overview]
Message-ID: <5262FB46.4030606@macke.de> (raw)
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>
---
hw/openrisc/cputimer.c | 29 +++++++++++++++++++----------
target-openrisc/cpu.h | 1 +
target-openrisc/sys_helper.c | 38 ++++++++++++++++++--------------------
3 files changed, 38 insertions(+), 30 deletions(-)
diff --git a/hw/openrisc/cputimer.c b/hw/openrisc/cputimer.c
index 988ca20..9c54945 100644
--- a/hw/openrisc/cputimer.c
+++ b/hw/openrisc/cputimer.c
@@ -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)
diff --git a/target-openrisc/cpu.h b/target-openrisc/cpu.h
index 8fd0bc0..0f9efdf 100644
--- a/target-openrisc/cpu.h
+++ b/target-openrisc/cpu.h
@@ -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);
diff --git a/target-openrisc/sys_helper.c b/target-openrisc/sys_helper.c
index cccbc0e..43fd93f 100644
--- a/target-openrisc/sys_helper.c
+++ b/target-openrisc/sys_helper.c
@@ -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:
-- 1.7.9.5
reply other threads:[~2013-10-19 21:36 UTC|newest]
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