| /* |
| * 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. |
| * |
| */ |
| |
| #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; |
| |
| printk(KERN_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"); |