diff options
Diffstat (limited to 'grub-core/kern/i386/tsc.c')
-rw-r--r-- | grub-core/kern/i386/tsc.c | 78 |
1 files changed, 78 insertions, 0 deletions
diff --git a/grub-core/kern/i386/tsc.c b/grub-core/kern/i386/tsc.c new file mode 100644 index 0000000..9293b16 --- /dev/null +++ b/grub-core/kern/i386/tsc.c @@ -0,0 +1,78 @@ +/* kern/i386/tsc.c - x86 TSC time source implementation + * Requires Pentium or better x86 CPU that supports the RDTSC instruction. + * This module calibrates the TSC to real time. + * + * GRUB -- GRand Unified Bootloader + * Copyright (C) 2008 Free Software Foundation, Inc. + * + * GRUB is free software: you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation, either version 3 of the License, or + * (at your option) any later version. + * + * GRUB 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. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with GRUB. If not, see <http://www.gnu.org/licenses/>. + */ + +#include <grub/types.h> +#include <grub/time.h> +#include <grub/misc.h> +#include <grub/i386/tsc.h> +#include <grub/i386/cpuid.h> + +/* This defines the value TSC had at the epoch (that is, when we calibrated it). */ +static grub_uint64_t tsc_boot_time; + +/* Calibrated TSC rate. (In ms per 2^32 ticks) */ +/* We assume that the tick is less than 1 ms and hence this value fits + in 32-bit. */ +grub_uint32_t grub_tsc_rate; + +static grub_uint64_t +grub_tsc_get_time_ms (void) +{ + grub_uint64_t a = grub_get_tsc () - tsc_boot_time; + grub_uint64_t ah = a >> 32; + grub_uint64_t al = a & 0xffffffff; + + return ((al * grub_tsc_rate) >> 32) + ah * grub_tsc_rate; +} + +static int +calibrate_tsc_hardcode (void) +{ + grub_tsc_rate = 5368;/* 800 MHz */ + return 1; +} + +void +grub_tsc_init (void) +{ + if (!grub_cpu_is_tsc_supported ()) + { +#if defined (GRUB_MACHINE_PCBIOS) || defined (GRUB_MACHINE_IEEE1275) + grub_install_get_time_ms (grub_rtc_get_time_ms); +#else + grub_fatal ("no TSC found"); +#endif + return; + } + + tsc_boot_time = grub_get_tsc (); + +#if defined (GRUB_MACHINE_XEN) || defined (GRUB_MACHINE_XEN_PVH) + (void) (grub_tsc_calibrate_from_xen () || calibrate_tsc_hardcode()); +#elif defined (GRUB_MACHINE_EFI) + (void) (grub_tsc_calibrate_from_pmtimer () || grub_tsc_calibrate_from_pit () || grub_tsc_calibrate_from_efi() || calibrate_tsc_hardcode()); +#elif defined (GRUB_MACHINE_COREBOOT) + (void) (grub_tsc_calibrate_from_pmtimer () || grub_tsc_calibrate_from_pit () || calibrate_tsc_hardcode()); +#else + (void) (grub_tsc_calibrate_from_pit () || calibrate_tsc_hardcode()); +#endif + grub_install_get_time_ms (grub_tsc_get_time_ms); +} |