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From: "Philippe Mathieu-Daudé" <f4bug@amsat.org>
To: Peter Maydell <peter.maydell@linaro.org>,
	qemu-devel@nongnu.org, Damien Hedde <damien.hedde@greensocs.com>
Cc: "Edgar E. Iglesias" <edgar.iglesias@xilinx.com>,
	Alistair Francis <alistair.francis@wdc.com>,
	Luc Michel <luc.michel@greensocs.com>
Subject: Re: [PULL 09/31] hw/core/clock: introduce clock object
Date: Sat, 17 Oct 2020 13:47:35 +0200	[thread overview]
Message-ID: <f295c99f-0405-1c26-6f58-12abdec8bd3d@amsat.org> (raw)
In-Reply-To: <20200430115142.13430-10-peter.maydell@linaro.org>

Hi Damien, Peter,

On 4/30/20 1:51 PM, Peter Maydell wrote:
> This object may be used to represent a clock inside a clock tree.
> 
> A clock may be connected to another clock so that it receives update,
> through a callback, whenever the source/parent clock is updated.
> 
> Although only the root clock of a clock tree controls the values
> (represented as periods) of all clocks in tree, each clock holds
> a local state containing the current value so that it can be fetched
> independently. It will allows us to fullfill migration requirements
> by migrating each clock independently of others.
> 
> This is based on the original work of Frederic Konrad.
> 
> Signed-off-by: Damien Hedde <damien.hedde@greensocs.com>
> Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
> Reviewed-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
> Message-id: 20200406135251.157596-2-damien.hedde@greensocs.com
> [PMM: Use uint64_t rather than unsigned long long in trace events;
>   the dtrace backend can't handle the latter]
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>   hw/core/Makefile.objs |   1 +
>   include/hw/clock.h    | 216 ++++++++++++++++++++++++++++++++++++++++++
>   hw/core/clock.c       | 130 +++++++++++++++++++++++++
>   hw/core/trace-events  |   7 ++
>   4 files changed, 354 insertions(+)
>   create mode 100644 include/hw/clock.h
>   create mode 100644 hw/core/clock.c
> 
> diff --git a/hw/core/Makefile.objs b/hw/core/Makefile.objs
> index 6215e7c2085..1d9b0aa2057 100644
> --- a/hw/core/Makefile.objs
> +++ b/hw/core/Makefile.objs
> @@ -7,6 +7,7 @@ common-obj-y += hotplug.o
>   common-obj-y += vmstate-if.o
>   # irq.o needed for qdev GPIO handling:
>   common-obj-y += irq.o
> +common-obj-y += clock.o
>   
>   common-obj-$(CONFIG_SOFTMMU) += reset.o
>   common-obj-$(CONFIG_SOFTMMU) += qdev-fw.o
> diff --git a/include/hw/clock.h b/include/hw/clock.h
> new file mode 100644
> index 00000000000..82a7f3c6982
> --- /dev/null
> +++ b/include/hw/clock.h
> @@ -0,0 +1,216 @@
> +/*
> + * Hardware Clocks
> + *
> + * Copyright GreenSocs 2016-2020
> + *
> + * Authors:
> + *  Frederic Konrad
> + *  Damien Hedde
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + */
> +
> +#ifndef QEMU_HW_CLOCK_H
> +#define QEMU_HW_CLOCK_H
> +
> +#include "qom/object.h"
> +#include "qemu/queue.h"
> +
> +#define TYPE_CLOCK "clock"
> +#define CLOCK(obj) OBJECT_CHECK(Clock, (obj), TYPE_CLOCK)
> +
> +typedef void ClockCallback(void *opaque);
> +
> +/*
> + * clock store a value representing the clock's period in 2^-32ns unit.
> + * It can represent:
> + *  + periods from 2^-32ns up to 4seconds
> + *  + frequency from ~0.25Hz 2e10Ghz
> + * Resolution of frequency representation decreases with frequency:
> + * + at 100MHz, resolution is ~2mHz
> + * + at 1Ghz,   resolution is ~0.2Hz
> + * + at 10Ghz,  resolution is ~20Hz
> + */
> +#define CLOCK_SECOND (1000000000llu << 32)
> +
> +/*
> + * macro helpers to convert to hertz / nanosecond
> + */
> +#define CLOCK_PERIOD_FROM_NS(ns) ((ns) * (CLOCK_SECOND / 1000000000llu))
> +#define CLOCK_PERIOD_TO_NS(per) ((per) / (CLOCK_SECOND / 1000000000llu))
> +#define CLOCK_PERIOD_FROM_HZ(hz) (((hz) != 0) ? CLOCK_SECOND / (hz) : 0u)

I'm having Floating Point Exception using a frequency of 1GHz.

Using frequency >=1GHz we have CLOCK_PERIOD_FROM_HZ(hz) > 0x100000000.

Then CLOCK_PERIOD_TO_NS(0x100000000) = 0.

So for frequency >=1GHz clock_get_ns() returns 0.

> +#define CLOCK_PERIOD_TO_HZ(per) (((per) != 0) ? CLOCK_SECOND / (per) : 0u)
> +
[...]


  parent reply	other threads:[~2020-10-17 11:48 UTC|newest]

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-30 11:51 [PULL 00/31] target-arm queue Peter Maydell
2020-04-30 11:51 ` [PULL 01/31] dma/xlnx-zdma: Fix descriptor loading (MEM) wrt endianness Peter Maydell
2020-04-30 11:51 ` [PULL 02/31] dma/xlnx-zdma: Fix descriptor loading (REG) " Peter Maydell
2020-04-30 11:51 ` [PULL 03/31] nrf51: Fix last GPIO CNF address Peter Maydell
2020-04-30 11:51 ` [PULL 04/31] bugfix: Use gicr_typer in arm_gicv3_icc_reset Peter Maydell
2020-04-30 11:51 ` [PULL 05/31] Typo: Correct the name of CPU hotplug memory region Peter Maydell
2020-04-30 11:51 ` [PULL 06/31] hw/net: Add Smartfusion2 emac block Peter Maydell
2020-04-30 11:51 ` [PULL 07/31] msf2: Add EMAC block to SmartFusion2 SoC Peter Maydell
2020-04-30 11:51 ` [PULL 08/31] tests/boot_linux_console: Add ethernet test to SmartFusion2 Peter Maydell
2020-04-30 11:51 ` [PULL 09/31] hw/core/clock: introduce clock object Peter Maydell
2020-04-30 14:35   ` Peter Maydell
2020-10-17 11:47   ` Philippe Mathieu-Daudé [this message]
2020-10-20 16:06     ` Philippe Mathieu-Daudé
2020-10-20 16:46       ` Peter Maydell
2020-10-20 17:46         ` Philippe Mathieu-Daudé
2020-04-30 11:51 ` [PULL 10/31] hw/core/clock-vmstate: define a vmstate entry for clock state Peter Maydell
2020-04-30 11:51 ` [PULL 11/31] qdev: add clock input&output support to devices Peter Maydell
2020-04-30 11:51 ` [PULL 12/31] qdev-clock: introduce an init array to ease the device construction Peter Maydell
2020-04-30 11:51 ` [PULL 13/31] docs/clocks: add device's clock documentation Peter Maydell
2020-04-30 11:51 ` [PULL 14/31] hw/misc/zynq_slcr: add clock generation for uarts Peter Maydell
2020-04-30 11:51 ` [PULL 15/31] hw/char/cadence_uart: add clock support Peter Maydell
2020-04-30 11:51 ` [PULL 16/31] hw/arm/xilinx_zynq: connect uart clocks to slcr Peter Maydell
2020-04-30 11:51 ` [PULL 17/31] qdev-monitor: print the device's clock with info qtree Peter Maydell
2020-04-30 11:51 ` [PULL 18/31] hw/arm: versal: Setup the ADMA with 128bit bus-width Peter Maydell
2020-04-30 11:51 ` [PULL 19/31] Cadence: gem: fix wraparound in 64bit descriptors Peter Maydell
2020-04-30 11:51 ` [PULL 20/31] net: cadence_gem: clear RX control descriptor Peter Maydell
2020-04-30 11:51 ` [PULL 21/31] target/arm: Vectorize integer comparison vs zero Peter Maydell
2020-04-30 11:51 ` [PULL 22/31] hw/arm/virt: dt: move creation of /secure-chosen to create_fdt() Peter Maydell
2020-04-30 11:51 ` [PULL 23/31] hw/arm/virt: dt: add kaslr-seed property Peter Maydell
2020-04-30 11:51 ` [PULL 24/31] target/arm: Restrict the Address Translate write operation to TCG accel Peter Maydell
2020-04-30 11:51 ` [PULL 25/31] target/arm: Make cpu_register() available for other files Peter Maydell
2020-04-30 11:51 ` [PULL 26/31] target/arm/cpu: Use ARRAY_SIZE() to iterate over ARMCPUInfo[] Peter Maydell
2020-04-30 14:30   ` Peter Maydell
2020-04-30 11:51 ` [PULL 27/31] target/arm/cpu: Update coding style to make checkpatch.pl happy Peter Maydell
2020-04-30 14:52   ` Philippe Mathieu-Daudé
2020-04-30 11:51 ` [PULL 28/31] device_tree: Allow name wildcards in qemu_fdt_node_path() Peter Maydell
2020-04-30 11:51 ` [PULL 29/31] device_tree: Constify compat " Peter Maydell
2020-04-30 11:51 ` [PULL 30/31] hw/arm: xlnx-zcu102: Move arm_boot_info into XlnxZCU102 Peter Maydell
2020-04-30 11:51 ` [PULL 31/31] hw/arm: xlnx-zcu102: Disable unsupported FDT firmware nodes Peter Maydell
2020-05-01  2:05 ` [PULL 00/31] target-arm queue no-reply

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