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[Qemu-devel] [PULL 5/9] openrisc: remove muldiv64()
From: |
Laurent Vivier |
Subject: |
[Qemu-devel] [PULL 5/9] openrisc: remove muldiv64() |
Date: |
Fri, 25 Sep 2015 16:09:06 +0200 |
Originally, timers were ticks based, and it made sense to
add ticks to current time to know when to trigger an alarm.
But since commit:
7447545 change all other clock references to use nanosecond resolution accessors
All timers use nanoseconds and we need to convert ticks to nanoseconds, by
doing something like:
y = muldiv64(x, get_ticks_per_sec(), TIMER_FREQ)
where x is the number of device ticks and y the number of system ticks.
y is used as nanoseconds in timer functions,
it works because 1 tick is 1 nanosecond.
(get_ticks_per_sec() is 10^9)
But as openrisc timer frequency is 20 MHz, we can also do:
y = x * 50; /* 20 MHz period is 50 ns */
Signed-off-by: Laurent Vivier <address@hidden>
---
hw/openrisc/cputimer.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/hw/openrisc/cputimer.c b/hw/openrisc/cputimer.c
index 9c54945..560cb91 100644
--- a/hw/openrisc/cputimer.c
+++ b/hw/openrisc/cputimer.c
@@ -22,7 +22,7 @@
#include "hw/hw.h"
#include "qemu/timer.h"
-#define TIMER_FREQ (20 * 1000 * 1000) /* 20MHz */
+#define TIMER_PERIOD 50 /* 50 ns period for 20 MHz timer */
/* The time when TTCR changes */
static uint64_t last_clk;
@@ -36,8 +36,7 @@ void cpu_openrisc_count_update(OpenRISCCPU *cpu)
return;
}
now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
- cpu->env.ttcr += (uint32_t)muldiv64(now - last_clk, TIMER_FREQ,
- get_ticks_per_sec());
+ cpu->env.ttcr += (uint32_t)((now - last_clk) / TIMER_PERIOD);
last_clk = now;
}
@@ -59,7 +58,7 @@ void cpu_openrisc_timer_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);
+ next = now + (uint64_t)wait * TIMER_PERIOD;
timer_mod(cpu->env.timer, next);
}
--
2.1.0
- [Qemu-devel] [PULL 0/9] muldiv64 queue, Laurent Vivier, 2015/09/25
- [Qemu-devel] [PULL 2/9] rtl8139: remove muldiv64(), Laurent Vivier, 2015/09/25
- [Qemu-devel] [PULL 4/9] mips: remove muldiv64(), Laurent Vivier, 2015/09/25
- [Qemu-devel] [PULL 1/9] i6300esb: remove muldiv64(), Laurent Vivier, 2015/09/25
- [Qemu-devel] [PULL 3/9] pcnet: remove muldiv64(), Laurent Vivier, 2015/09/25
- [Qemu-devel] [PULL 9/9] net: remove muldiv64(), Laurent Vivier, 2015/09/25
- [Qemu-devel] [PULL 8/9] bt: remove muldiv64(), Laurent Vivier, 2015/09/25
- [Qemu-devel] [PULL 7/9] hpet: remove muldiv64(), Laurent Vivier, 2015/09/25
- [Qemu-devel] [PULL 5/9] openrisc: remove muldiv64(),
Laurent Vivier <=
- [Qemu-devel] [PULL 6/9] arm: clarify the use of muldiv64(), Laurent Vivier, 2015/09/25
- Re: [Qemu-devel] [PULL 0/9] muldiv64 queue, Peter Maydell, 2015/09/25