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Re: [Qemu-trivial] [PATCH v2 1/7] PCI: remove muldiv64()
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-trivial] [PATCH v2 1/7] PCI: remove muldiv64() |
Date: |
Thu, 27 Aug 2015 14:12:49 +0300 |
On Wed, Aug 26, 2015 at 08:05:32PM +0200, Laurent Vivier wrote:
> 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>
I think you should split this with a patch per devices.
Otherwise, it's up to net maintainers: pls Cc them all.
And I don't think qemu-trivial is appropriate here.
> ---
> hw/net/pcnet.c | 3 +--
> hw/net/rtl8139.c | 14 ++++++--------
> hw/watchdog/wdt_i6300esb.c | 11 +++--------
> tests/rtl8139-test.c | 2 +-
> 4 files changed, 11 insertions(+), 19 deletions(-)
>
> diff --git a/hw/net/pcnet.c b/hw/net/pcnet.c
> index 3437376..0eb3cc4 100644
> --- a/hw/net/pcnet.c
> +++ b/hw/net/pcnet.c
> @@ -670,8 +670,7 @@ static inline hwaddr pcnet_rdra_addr(PCNetState *s, int
> idx)
> static inline int64_t pcnet_get_next_poll_time(PCNetState *s, int64_t
> current_time)
> {
> int64_t next_time = current_time +
> - muldiv64(65536 - (CSR_SPND(s) ? 0 : CSR_POLL(s)),
> - get_ticks_per_sec(), 33000000L);
> + (65536 - (CSR_SPND(s) ? 0 : CSR_POLL(s))) * 30;
> if (next_time <= current_time)
> next_time = current_time + 1;
> return next_time;
> diff --git a/hw/net/rtl8139.c b/hw/net/rtl8139.c
> index edbb61c..1e119e6 100644
> --- a/hw/net/rtl8139.c
> +++ b/hw/net/rtl8139.c
> @@ -63,7 +63,7 @@
> /* debug RTL8139 card */
> //#define DEBUG_RTL8139 1
>
> -#define PCI_FREQUENCY 33000000L
> +#define PCI_PERIOD 30 /* 30 ns period = 33.333333 Mhz frequency */
>
> #define SET_MASKED(input, mask, curr) \
> ( ( (input) & ~(mask) ) | ( (curr) & (mask) ) )
Pls rename this RTL8139_PCI_PERIOD to avoid namespace pollution.
> @@ -2881,8 +2881,7 @@ static void rtl8139_io_writew(void *opaque, uint8_t
> addr, uint32_t val)
>
> static void rtl8139_set_next_tctr_time(RTL8139State *s)
> {
> - const uint64_t ns_per_period =
> - muldiv64(0x100000000LL, get_ticks_per_sec(), PCI_FREQUENCY);
> + const uint64_t ns_per_period = (uint64_t)PCI_PERIOD << 32;
>
> DPRINTF("entered rtl8139_set_next_tctr_time\n");
>
> @@ -2900,7 +2899,7 @@ static void rtl8139_set_next_tctr_time(RTL8139State *s)
> if (!s->TimerInt) {
> timer_del(s->timer);
> } else {
> - uint64_t delta = muldiv64(s->TimerInt, get_ticks_per_sec(),
> PCI_FREQUENCY);
> + uint64_t delta = (uint64_t)s->TimerInt * PCI_PERIOD;
> if (s->TCTR_base + delta <= qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL)) {
> delta += ns_per_period;
> }
> @@ -3174,8 +3173,8 @@ static uint32_t rtl8139_io_readl(void *opaque, uint8_t
> addr)
> break;
>
> case Timer:
> - ret = muldiv64(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) -
> s->TCTR_base,
> - PCI_FREQUENCY, get_ticks_per_sec());
> + ret = (qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) - s->TCTR_base) /
> + PCI_PERIOD;
> DPRINTF("TCTR Timer read val=0x%08x\n", ret);
> break;
>
> @@ -3269,8 +3268,7 @@ static void rtl8139_pre_save(void *opaque)
> int64_t current_time = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
>
> /* for migration to older versions */
> - s->TCTR = muldiv64(current_time - s->TCTR_base, PCI_FREQUENCY,
> - get_ticks_per_sec());
> + s->TCTR = (current_time - s->TCTR_base) / PCI_PERIOD;
> s->rtl8139_mmio_io_addr_dummy = 0;
> }
>
> diff --git a/hw/watchdog/wdt_i6300esb.c b/hw/watchdog/wdt_i6300esb.c
> index cfa2b1b..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(get_ticks_per_sec(), timeout, 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);
>
> diff --git a/tests/rtl8139-test.c b/tests/rtl8139-test.c
> index e749be3..ba62851 100644
> --- a/tests/rtl8139-test.c
> +++ b/tests/rtl8139-test.c
> @@ -20,7 +20,7 @@ static void nop(void)
> {
> }
>
> -#define CLK 33000000
> +#define CLK 33333333
>
> static QPCIBus *pcibus;
> static QPCIDevice *dev;
> --
> 2.1.0
- [Qemu-trivial] [PATCH v2 0/7] remove useless muldiv64(), Laurent Vivier, 2015/08/26
- [Qemu-trivial] [PATCH v2 1/7] PCI: remove muldiv64(), Laurent Vivier, 2015/08/26
- Re: [Qemu-trivial] [PATCH v2 1/7] PCI: remove muldiv64(),
Michael S. Tsirkin <=
- [Qemu-trivial] [PATCH v2 3/7] openrisc: remove muldiv64(), Laurent Vivier, 2015/08/26
- [Qemu-trivial] [PATCH v2 2/7] mips: remove muldiv64(), Laurent Vivier, 2015/08/26
- [Qemu-trivial] [PATCH v2 5/7] hpet: remove muldiv64(), Laurent Vivier, 2015/08/26
- [Qemu-trivial] [PATCH v2 4/7] arm: clarify the use of muldiv64(), Laurent Vivier, 2015/08/26
- [Qemu-trivial] [PATCH v2 7/7] net: remove muldiv64(), Laurent Vivier, 2015/08/26
- [Qemu-trivial] [PATCH v2 6/7] bt: remove muldiv64(), Laurent Vivier, 2015/08/26