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[Qemu-devel] [PULL 1/9] i6300esb: remove muldiv64()
From: |
Laurent Vivier |
Subject: |
[Qemu-devel] [PULL 1/9] i6300esb: remove muldiv64() |
Date: |
Fri, 25 Sep 2015 16:09:02 +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(), PCI_FREQUENCY)
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 PCI frequency is 33 MHz, we can also do:
y = x * 30; /* 33 MHz PCI period is 30 ns */
Which is much more simple.
This implies a 33.333333 MHz PCI frequency,
but this is correct.
Signed-off-by: Laurent Vivier <address@hidden>
---
hw/watchdog/wdt_i6300esb.c | 11 +++--------
1 file changed, 3 insertions(+), 8 deletions(-)
diff --git a/hw/watchdog/wdt_i6300esb.c b/hw/watchdog/wdt_i6300esb.c
index 3e07d44..a91c8fd 100644
--- a/hw/watchdog/wdt_i6300esb.c
+++ b/hw/watchdog/wdt_i6300esb.c
@@ -129,14 +129,9 @@ static void i6300esb_restart_timer(I6300State *d, int
stage)
else
timeout <<= 5;
- /* Get the timeout in units of ticks_per_sec.
- *
- * ticks_per_sec is typically 10^9 == 0x3B9ACA00 (30 bits), with
- * 20 bits of user supplied preload, and 15 bits of scale, the
- * multiply here can exceed 64-bits, before we divide by 33MHz, so
- * we use a higher-precision intermediate result.
- */
- timeout = muldiv64(timeout, get_ticks_per_sec(), 33000000);
+ /* Get the timeout in nanoseconds. */
+
+ timeout = timeout * 30; /* on a PCI bus, 1 tick is 30 ns*/
i6300esb_debug("stage %d, timeout %" PRIi64 "\n", d->stage, timeout);
--
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 <=
- [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, 2015/09/25
- [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