vbatts/grub
1
0
Fork 0
Code Issues Pull requests Releases Wiki Activity

tsc: Use alternative delay sources whenever appropriate.

Browse source 
PIT isn't available on some of new hardware including Hyper-V. So
use pmtimer for calibration. Moreover pmtimer calibration is faster, so
use it on coreboor where booting time is important.

Based on patch by Michael Chang.
This commit is contained in:
Vladimir Serbinenko 2015-11-13 16:14:53 +01:00
parent 3d2c8048da
commit d43a5ee651
13 changed files with 451 additions and 121 deletions
Download patch file Download diff file Expand all files Collapse all files

40
grub-core/kern/i386/xen/tsc.c Normal file
View file

@ -0,0 +1,40 @@
/* kern/i386/tsc.c - x86 TSC time source implementation
* Requires Pentium or better x86 CPU that supports the RDTSC instruction.
* This module uses the PIT to calibrate 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/xen.h>
int
grub_tsc_calibrate_from_xen (void)
{
grub_uint64_t t;
t = grub_xen_shared_info->vcpu_info[0].time.tsc_to_system_mul;
if (grub_xen_shared_info->vcpu_info[0].time.tsc_shift > 0)
t <<= grub_xen_shared_info->vcpu_info[0].time.tsc_shift;
else
t >>= -grub_xen_shared_info->vcpu_info[0].time.tsc_shift;
grub_tsc_rate = grub_divmod64 (t, 1000000, 0);
return 1;
}