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/*
* A clocksource for Linux running on HyperV.
*
*
* Copyright (C) 2010, Novell, Inc.
* Author : K. Y. Srinivasan <ksrinivasan@novell.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
* NON INFRINGEMENT. See the GNU General Public License for more
* details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/version.h>
#include <linux/clocksource.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/pci.h>
#include <linux/dmi.h>
#include <asm/hyperv.h>
#include <asm/mshyperv.h>
#include <asm/hypervisor.h>
#define HV_CLOCK_SHIFT 22
static cycle_t read_hv_clock(struct clocksource *arg)
{
cycle_t current_tick;
/*
* Read the partition counter to get the current tick count. This count
* is set to 0 when the partition is created and is incremented in
* 100 nanosecond units.
*/
rdmsrl(HV_X64_MSR_TIME_REF_COUNT, current_tick);
return current_tick;
}
static struct clocksource hyperv_cs = {
.name = "hyperv_clocksource",
.rating = 400, /* use this when running on Hyperv*/
.read = read_hv_clock,
.mask = CLOCKSOURCE_MASK(64),
/*
* The time ref counter in HyperV is in 100ns units.
* The definition of mult is:
* mult/2^shift = ns/cyc = 100
* mult = (100 << shift)
*/
.mult = (100 << HV_CLOCK_SHIFT),
.shift = HV_CLOCK_SHIFT,
};
static const struct dmi_system_id __initconst
hv_timesource_dmi_table[] __maybe_unused = {
{
.ident = "Hyper-V",
.matches = {
DMI_MATCH(DMI_SYS_VENDOR, "Microsoft Corporation"),
DMI_MATCH(DMI_PRODUCT_NAME, "Virtual Machine"),
DMI_MATCH(DMI_BOARD_NAME, "Virtual Machine"),
},
},
{ },
};
MODULE_DEVICE_TABLE(dmi, hv_timesource_dmi_table);
static const struct pci_device_id __initconst
hv_timesource_pci_table[] __maybe_unused = {
{ PCI_DEVICE(0x1414, 0x5353) }, /* VGA compatible controller */
{ 0 }
};
MODULE_DEVICE_TABLE(pci, hv_timesource_pci_table);
static int __init init_hv_clocksource(void)
{
if ((x86_hyper != &x86_hyper_ms_hyperv) ||
!(ms_hyperv.features & HV_X64_MSR_TIME_REF_COUNT_AVAILABLE))
return -ENODEV;
if (!dmi_check_system(hv_timesource_dmi_table))
return -ENODEV;
pr_info("Registering HyperV clock source\n");
return clocksource_register(&hyperv_cs);
}
module_init(init_hv_clocksource);
MODULE_DESCRIPTION("HyperV based clocksource");
MODULE_AUTHOR("K. Y. Srinivasan <ksrinivasan@novell.com>");
MODULE_LICENSE("GPL");
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