From 603f5c1a20ec0acd20227eb4c48ffc4d21960ec1 Mon Sep 17 00:00:00 2001
From: Laszlo Ersek <lersek@redhat.com>
Date: Fri, 10 Oct 2014 11:11:09 +0200
Subject: [PATCH 131/194] calibrate_tsc(): use the Stall() EFI boot service on
 GRUB_MACHINE_EFI

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1150698

HyperV Gen2 virtual machines have no PIT; guest code should rely on UEFI
services instead.

Signed-off-by: RHEL Ninjas <example@example.com>
---
 grub-core/kern/i386/tsc.c | 59 ++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 58 insertions(+), 1 deletion(-)

diff --git a/grub-core/kern/i386/tsc.c b/grub-core/kern/i386/tsc.c
index 2e85289d8..48c013860 100644
--- a/grub-core/kern/i386/tsc.c
+++ b/grub-core/kern/i386/tsc.c
@@ -24,6 +24,17 @@
 #include <grub/misc.h>
 #include <grub/i386/tsc.h>
 #include <grub/i386/cpuid.h>
+#ifdef GRUB_MACHINE_XEN
+# include <grub/xen.h>
+#else
+# ifdef GRUB_MACHINE_EFI
+#  include <grub/efi/efi.h>
+#  include <grub/efi/api.h>
+# else
+#  include <grub/i386/pit.h>
+# endif
+#endif
+#include <grub/cpu/io.h>
 
 /* This defines the value TSC had at the epoch (that is, when we calibrated it). */
 static grub_uint64_t tsc_boot_time;
@@ -33,6 +44,44 @@ static grub_uint64_t tsc_boot_time;
    in 32-bit.  */
 grub_uint32_t grub_tsc_rate;
 
+#ifndef GRUB_MACHINE_XEN
+
+static void
+grub_stall (grub_uint16_t tics)
+{
+# ifdef GRUB_MACHINE_EFI
+  grub_uint64_t microseconds;
+
+  microseconds = (grub_uint64_t)tics * 1000 * 1000 * 3 / 3579545;
+  efi_call_1 (grub_efi_system_table->boot_services->stall, microseconds);
+# else
+  /* Disable timer2 gate and speaker.  */
+  grub_outb (grub_inb (GRUB_PIT_SPEAKER_PORT)
+	     & ~ (GRUB_PIT_SPK_DATA | GRUB_PIT_SPK_TMR2),
+             GRUB_PIT_SPEAKER_PORT);
+
+  /* Set tics.  */
+  grub_outb (GRUB_PIT_CTRL_SELECT_2 | GRUB_PIT_CTRL_READLOAD_WORD,
+	     GRUB_PIT_CTRL);
+  grub_outb (tics & 0xff, GRUB_PIT_COUNTER_2);
+  grub_outb (tics >> 8, GRUB_PIT_COUNTER_2);
+
+  /* Enable timer2 gate, keep speaker disabled.  */
+  grub_outb ((grub_inb (GRUB_PIT_SPEAKER_PORT) & ~ GRUB_PIT_SPK_DATA)
+	     | GRUB_PIT_SPK_TMR2,
+             GRUB_PIT_SPEAKER_PORT);
+
+  /* Wait.  */
+  while ((grub_inb (GRUB_PIT_SPEAKER_PORT) & GRUB_PIT_SPK_TMR2_LATCH) == 0x00);
+
+  /* Disable timer2 gate and speaker.  */
+  grub_outb (grub_inb (GRUB_PIT_SPEAKER_PORT)
+	     & ~ (GRUB_PIT_SPK_DATA | GRUB_PIT_SPK_TMR2),
+             GRUB_PIT_SPEAKER_PORT);
+# endif
+}
+#endif
+
 static grub_uint64_t
 grub_tsc_get_time_ms (void)
 {
@@ -46,7 +95,15 @@ grub_tsc_get_time_ms (void)
 static int
 calibrate_tsc_hardcode (void)
 {
-  grub_tsc_rate = 5368;/* 800 MHz */
+  /* First calibrate the TSC rate (relative, not absolute time). */
+  grub_uint64_t end_tsc;
+
+  tsc_boot_time = grub_get_tsc ();
+  grub_stall (0xffff);
+  end_tsc = grub_get_tsc ();
+
+  grub_tsc_rate = grub_divmod64 ((55ULL << 32), end_tsc - tsc_boot_time, 0);
+
   return 1;
 }
 
-- 
2.13.5