From: Laurent Vivier <lvivier@redhat.com>
To: qemu-devel@nongnu.org, Jia Liu <proljc@gmail.com>
Subject: [Qemu-devel] [PATCH v3 5/9] openrisc: remove muldiv64()
Date: Thu, 27 Aug 2015 21:33:03 +0200 [thread overview]
Message-ID: <1440703987-29012-6-git-send-email-lvivier@redhat.com> (raw)
In-Reply-To: <1440703987-29012-1-git-send-email-lvivier@redhat.com>
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 <lvivier@redhat.com>
---
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
next prev parent reply other threads:[~2015-08-27 19:33 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-08-27 19:32 [Qemu-devel] [PATCH v3 0/9] remove useless muldiv64() Laurent Vivier
2015-08-27 19:32 ` [Qemu-devel] [PATCH v3 1/9] i6300esb: remove muldiv64() Laurent Vivier
2015-09-14 13:31 ` [Qemu-devel] [PATCH v4 " Laurent Vivier
2015-08-27 19:33 ` [Qemu-devel] [PATCH v3 2/9] rtl8139: " Laurent Vivier
2015-08-28 14:12 ` Stefan Hajnoczi
2015-08-27 19:33 ` [Qemu-devel] [PATCH v3 3/9] pcnet: " Laurent Vivier
2015-08-28 14:12 ` Stefan Hajnoczi
2015-08-27 19:33 ` [Qemu-devel] [PATCH v3 4/9] mips: " Laurent Vivier
2015-09-08 12:54 ` Laurent Vivier
2015-09-08 13:42 ` Leon Alrae
2015-08-27 19:33 ` Laurent Vivier [this message]
2015-09-08 12:54 ` [Qemu-devel] [PATCH v3 5/9] openrisc: " Laurent Vivier
2015-08-27 19:33 ` [Qemu-devel] [PATCH v3 6/9] arm: clarify the use of muldiv64() Laurent Vivier
2015-08-27 20:23 ` Peter Crosthwaite
2015-09-01 11:17 ` Peter Maydell
2015-09-01 11:23 ` Laurent Vivier
2015-09-01 11:30 ` Peter Maydell
2015-08-27 19:33 ` [Qemu-devel] [PATCH v3 7/9] hpet: remove muldiv64() Laurent Vivier
2015-09-08 12:55 ` Laurent Vivier
2015-09-08 12:58 ` Paolo Bonzini
2015-08-27 19:33 ` [Qemu-devel] [PATCH v3 8/9] bt: " Laurent Vivier
2015-09-08 12:55 ` Laurent Vivier
2015-09-08 12:57 ` Paolo Bonzini
2015-08-27 19:33 ` [Qemu-devel] [PATCH v3 9/9] net: " Laurent Vivier
2015-08-28 14:12 ` Stefan Hajnoczi
2015-09-24 16:21 ` [Qemu-devel] [PATCH v3 0/9] remove useless muldiv64() Laurent Vivier
2015-09-25 10:31 ` Paolo Bonzini
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