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