diff options
Diffstat (limited to 'drivers/staging/hv/hv_timesource.c')
-rw-r--r-- | drivers/staging/hv/hv_timesource.c | 101 |
1 files changed, 101 insertions, 0 deletions
diff --git a/drivers/staging/hv/hv_timesource.c b/drivers/staging/hv/hv_timesource.c new file mode 100644 index 0000000..a7ee533 --- /dev/null +++ b/drivers/staging/hv/hv_timesource.c @@ -0,0 +1,101 @@ +/* + * 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"); |