1 files changed, 40 insertions, 0 deletions
diff --git a/grub-core/kern/i386/efi/tsc.c b/grub-core/kern/i386/efi/tsc.c
new file mode 100644
index 0000000..4b93ba8
--- /dev/null
+++ b/grub-core/kern/i386/efi/tsc.c
@@ -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/efi/efi.h>
+#include <grub/efi/api.h>
+
+int
+grub_tsc_calibrate_from_efi (void)
+{
+  grub_uint64_t start_tsc, end_tsc;
+  /* Use EFI Time Service to calibrate TSC */
+  start_tsc = grub_get_tsc ();
+  efi_call_1 (grub_efi_system_table->boot_services->stall, 1000);
+  end_tsc = grub_get_tsc ();
+  grub_tsc_rate = grub_divmod64 ((1ULL << 32), end_tsc - start_tsc, 0);
+  return 1;
+}