1 files changed, 88 insertions, 0 deletions
diff --git a/grub-core/kern/i386/tsc_pmtimer.c b/grub-core/kern/i386/tsc_pmtimer.c
new file mode 100644
index 0000000..c9c3616
--- /dev/null
+++ b/grub-core/kern/i386/tsc_pmtimer.c
@@ -0,0 +1,88 @@
+/* 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/i386/pmtimer.h>
+#include <grub/acpi.h>
+#include <grub/cpu/io.h>
+
+grub_uint64_t
+grub_pmtimer_wait_count_tsc (grub_port_t pmtimer,
+			     grub_uint16_t num_pm_ticks)
+{
+  grub_uint32_t start;
+  grub_uint32_t last;
+  grub_uint32_t cur, end;
+  grub_uint64_t start_tsc;
+  grub_uint64_t end_tsc;
+  int num_iter = 0;
+
+  start = grub_inl (pmtimer) & 0xffffff;
+  last = start;
+  end = start + num_pm_ticks;
+  start_tsc = grub_get_tsc ();
+  while (1)
+    {
+      cur = grub_inl (pmtimer) & 0xffffff;
+      if (cur < last)
+	cur |= 0x1000000;
+      num_iter++;
+      if (cur >= end)
+	{
+	  end_tsc = grub_get_tsc ();
+	  return end_tsc - start_tsc;
+	}
+      /* Check for broken PM timer.
+	 50000000 TSCs is between 5 ms (10GHz) and 200 ms (250 MHz)
+	 if after this time we still don't have 1 ms on pmtimer, then
+	 pmtimer is broken.
+       */
+      if ((num_iter & 0xffffff) == 0 && grub_get_tsc () - start_tsc > 5000000) {
+	return 0;
+      }
+    }
+}
+
+int
+grub_tsc_calibrate_from_pmtimer (void)
+{
+  struct grub_acpi_fadt *fadt;
+  grub_port_t pmtimer;
+  grub_uint64_t tsc_diff;
+
+  fadt = grub_acpi_find_fadt ();
+  if (!fadt)
+    return 0;
+  pmtimer = fadt->pmtimer;
+  if (!pmtimer)
+    return 0;
+
+  /* It's 3.579545 MHz clock. Wait 1 ms.  */
+  tsc_diff = grub_pmtimer_wait_count_tsc (pmtimer, 3580);
+  if (tsc_diff == 0)
+    return 0;
+  grub_tsc_rate = grub_divmod64 ((1ULL << 32), tsc_diff, 0);
+  return 1;
+}