diff options
| author | Sebastian Macke <sebastian@macke.de> | 2013-10-22 02:12:41 +0200 |
|---|---|---|
| committer | Jia Liu <proljc@gmail.com> | 2013-11-20 21:46:45 +0800 |
| commit | d51552176a2ab5e80a211514aa1339fe2575ec2a (patch) | |
| tree | f272c169ec8acfdd998b69d7d4eb1ab9af58708d /hw | |
| parent | ae52bd96ceaea36c486d8ffeb798e160f31d3be8 (diff) | |
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>
Diffstat (limited to 'hw')
| -rw-r--r-- | hw/openrisc/cputimer.c | 29 |
1 files changed, 19 insertions, 10 deletions
diff --git a/hw/openrisc/cputimer.c b/hw/openrisc/cputimer.c index 988ca20898..9c54945107 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) |