From d47c03e078f39034d1843dfe8a84aedff40638ba Mon Sep 17 00:00:00 2001

From: Vladimir 'phcoder' Serbinenko <phcoder@gmail.com>

Date: Sun, 10 Mar 2013 17:45:38 +0100

Subject: [PATCH 200/364] 	Avoid costly 64-bit division in

 grub_get_time_ms on most platforms.

---

 ChangeLog                     |  4 ++++

 grub-core/Makefile.am         | 14 ++++++------

 grub-core/Makefile.core.def   |  3 ---

 grub-core/kern/i386/pc/init.c |  6 +++---

 grub-core/kern/i386/pit.c     | 49 ------------------------------------------

 grub-core/kern/i386/tsc.c     | 50 +++++++++++++++++++++++++++++++++----------

 grub-core/loader/i386/xnu.c   | 28 +++++++++++++-----------

 include/grub/i386/pc/time.h   |  5 -----

 include/grub/i386/pit.h       |  2 --

 include/grub/i386/tsc.h       |  2 ++

 10 files changed, 70 insertions(+), 93 deletions(-)

 delete mode 100644 grub-core/kern/i386/pit.c

diff --git a/ChangeLog b/ChangeLog

index c604d8d..bc51ae9 100644

--- a/ChangeLog

+++ b/ChangeLog

@@ -1,5 +1,9 @@

 2013-03-10  Vladimir Serbinenko  <phcoder@gmail.com>

+	Avoid costly 64-bit division in grub_get_time_ms on most platforms.

+

+2013-03-10  Vladimir Serbinenko  <phcoder@gmail.com>

+

 	* grub-core/fs/fshelp.c (grub_fshelp_log2blksize): Remove now unused

 	function.

diff --git a/grub-core/Makefile.am b/grub-core/Makefile.am

index 9cb14e2..221466b 100644

--- a/grub-core/Makefile.am

+++ b/grub-core/Makefile.am

@@ -98,29 +98,29 @@ if COND_i386_pc

 KERNEL_HEADER_FILES += $(top_builddir)/include/grub/machine/kernel.h

 KERNEL_HEADER_FILES += $(top_builddir)/include/grub/machine/pxe.h

 KERNEL_HEADER_FILES += $(top_builddir)/include/grub/machine/int.h

-KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/i386/pit.h

+KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/i386/tsc.h

 endif

 if COND_i386_efi

 KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/efi/efi.h

 KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/efi/disk.h

-KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/i386/pit.h

+KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/i386/tsc.h

 KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/pci.h

 endif

 if COND_i386_coreboot

-KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/i386/pit.h

+KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/i386/tsc.h

 KERNEL_HEADER_FILES += $(top_builddir)/include/grub/i386/pc/int.h

 endif

 if COND_i386_multiboot

-KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/i386/pit.h

+KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/i386/tsc.h

 KERNEL_HEADER_FILES += $(top_builddir)/include/grub/i386/pc/int.h

 endif

 if COND_i386_qemu

 KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/pci.h

-KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/i386/pit.h

+KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/i386/tsc.h

 endif

 if COND_i386_ieee1275

@@ -128,13 +128,13 @@ KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/ieee1275/ieee1275.h

 KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/terminfo.h

 KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/extcmd.h

 KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/lib/arg.h

-KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/i386/pit.h

+KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/i386/tsc.h

 endif

 if COND_x86_64_efi

 KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/efi/efi.h

 KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/efi/disk.h

-KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/i386/pit.h

+KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/i386/tsc.h

 KERNEL_HEADER_FILES += $(top_srcdir)/include/grub/pci.h

 endif

diff --git a/grub-core/Makefile.core.def b/grub-core/Makefile.core.def

index 93ff2a8..3bcf662 100644

--- a/grub-core/Makefile.core.def

+++ b/grub-core/Makefile.core.def

@@ -102,7 +102,6 @@ kernel = {

   noemu_nodist = symlist.c;

-  i386_pc = kern/generic/rtc_get_time_ms.c;

   mips = kern/generic/rtc_get_time_ms.c;

   ieee1275 = disk/ieee1275/ofdisk.c;

@@ -123,8 +122,6 @@ kernel = {

   i386_coreboot_multiboot_qemu = kern/i386/coreboot/init.c;

   i386_coreboot_multiboot_qemu = term/i386/pc/vga_text.c;

-  x86 = kern/i386/pit.c;

-

   efi = disk/efi/efidisk.c;

   efi = kern/efi/efi.c;

   efi = kern/efi/init.c;

diff --git a/grub-core/kern/i386/pc/init.c b/grub-core/kern/i386/pc/init.c

index 730e04a..5b68504 100644

--- a/grub-core/kern/i386/pc/init.c

+++ b/grub-core/kern/i386/pc/init.c

@@ -52,8 +52,8 @@ void (*grub_pc_net_config) (char **device, char **path);

  *	return the real time in ticks, of which there are about

  *	18-20 per second

  */

-grub_uint32_t

-grub_get_rtc (void)

+grub_uint64_t

+grub_rtc_get_time_ms (void)

 {

   struct grub_bios_int_registers regs;

@@ -61,7 +61,7 @@ grub_get_rtc (void)

   regs.flags = GRUB_CPU_INT_FLAGS_DEFAULT;

   grub_bios_interrupt (0x1a, ®s;;

-  return (regs.ecx << 16) | (regs.edx & 0xffff);

+  return ((regs.ecx << 16) | (regs.edx & 0xffff)) * 55ULL;

 }

 void

diff --git a/grub-core/kern/i386/pit.c b/grub-core/kern/i386/pit.c

deleted file mode 100644

index 092481a..0000000

--- a/grub-core/kern/i386/pit.c

+++ /dev/null

@@ -1,49 +0,0 @@

-/*

- *  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/i386/io.h>

-#include <grub/i386/pit.h>

-

-void

-grub_pit_wait (grub_uint16_t tics)

-{

-  /* 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);

-}

diff --git a/grub-core/kern/i386/tsc.c b/grub-core/kern/i386/tsc.c

index c4645f0..9efd633 100644

--- a/grub-core/kern/i386/tsc.c

+++ b/grub-core/kern/i386/tsc.c

@@ -25,37 +25,66 @@

 #include <grub/misc.h>

 #include <grub/i386/tsc.h>

 #include <grub/i386/pit.h>

+#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;

-/* Calibrated TSC rate.  (In TSC ticks per millisecond.) */

-static grub_uint64_t tsc_ticks_per_ms;

+/* 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 void

+grub_pit_wait (grub_uint16_t tics)

+{

+  /* 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);

+}

 grub_uint64_t

 grub_tsc_get_time_ms (void)

 {

-  return tsc_boot_time + grub_divmod64 (grub_get_tsc (), tsc_ticks_per_ms, 0);

-}

+  grub_uint64_t a = grub_get_tsc () - tsc_boot_time;

+  grub_uint64_t ah = a >> 32;

+  grub_uint64_t al = a & 0xffffffff;

-

-/* How many RTC ticks to use for calibration loop. (>= 1) */

-#define CALIBRATION_TICKS 2

+  return ((al * grub_tsc_rate) >> 32) + ah * grub_tsc_rate;

+}

 /* Calibrate the TSC based on the RTC.  */

 static void

 calibrate_tsc (void)

 {

   /* First calibrate the TSC rate (relative, not absolute time). */

-  grub_uint64_t start_tsc;

   grub_uint64_t end_tsc;

-  start_tsc = grub_get_tsc ();

+  tsc_boot_time = grub_get_tsc ();

   grub_pit_wait (0xffff);

   end_tsc = grub_get_tsc ();

-  tsc_ticks_per_ms = grub_divmod64 (end_tsc - start_tsc, 55, 0);

+  grub_tsc_rate = grub_divmod64 ((55ULL << 32), end_tsc - tsc_boot_time, 0);

 }

 void

@@ -63,7 +92,6 @@ grub_tsc_init (void)

 {

   if (grub_cpu_is_tsc_supported ())

     {

-      tsc_boot_time = grub_get_tsc ();

       calibrate_tsc ();

       grub_install_get_time_ms (grub_tsc_get_time_ms);

     }

diff --git a/grub-core/loader/i386/xnu.c b/grub-core/loader/i386/xnu.c

index 4e5ce09..497529b 100644

--- a/grub-core/loader/i386/xnu.c

+++ b/grub-core/loader/i386/xnu.c

@@ -125,9 +125,6 @@ guessfsb (void)

 {

   const grub_uint64_t sane_value = 100000000;

   grub_uint32_t manufacturer[3], max_cpuid, capabilities, msrlow;

-  grub_uint64_t start_tsc;

-  grub_uint64_t end_tsc;

-  grub_uint64_t tsc_ticks_per_ms;

   if (! grub_cpu_is_cpuid_supported ())

     return sane_value;

@@ -192,14 +189,6 @@ guessfsb (void)

   if (! (capabilities & (1 << 7)))

     return sane_value;

-  /* Calibrate the TSC rate. */

-

-  start_tsc = grub_get_tsc ();

-  grub_pit_wait (0xffff);

-  end_tsc = grub_get_tsc ();

-

-  tsc_ticks_per_ms = grub_divmod64 (end_tsc - start_tsc, 55, 0);

-

   /* Read the multiplier. */

   asm volatile ("movl $0x198, %%ecx\n"

 		"rdmsr"

@@ -207,8 +196,21 @@ guessfsb (void)

 		:

 		: "%ecx", "%eax");

-  return grub_divmod64 (2000 * tsc_ticks_per_ms,

-			((msrlow >> 7) & 0x3e) + ((msrlow >> 14) & 1), 0);

+  grub_uint64_t v;

+  grub_uint32_t r;

+

+  /* (2000ULL << 32) / grub_tsc_rate  */

+  /* Assumption: TSC frequency is over 2 MHz.  */

+  v = 0xffffffff / grub_tsc_rate;

+  v *= 2000;

+  /* v is at most 2000 off from (2000ULL << 32) / grub_tsc_rate.

+     Since grub_tsc_rate < 2^32/2^11=2^21, so no overflow.

+   */

+  r = (2000ULL << 32) - v * grub_tsc_rate;

+  v += r / grub_tsc_rate;

+

+  return grub_divmod64 (v, ((msrlow >> 7) & 0x3e) | ((msrlow >> 14) & 1),

+			 0);

 }

 struct property_descriptor

diff --git a/include/grub/i386/pc/time.h b/include/grub/i386/pc/time.h

index ba227ca..e93320f 100644

--- a/include/grub/i386/pc/time.h

+++ b/include/grub/i386/pc/time.h

@@ -21,9 +21,4 @@

 #include <grub/symbol.h>

-#define GRUB_TICKS_PER_SECOND	18

-

-/* Return the real time in ticks.  */

-grub_uint32_t grub_get_rtc (void);

-

 #endif /* ! KERNEL_MACHINE_TIME_HEADER */

diff --git a/include/grub/i386/pit.h b/include/grub/i386/pit.h

index e1c92cd..4bd49d4 100644

--- a/include/grub/i386/pit.h

+++ b/include/grub/i386/pit.h

@@ -100,6 +100,4 @@ enum

     GRUB_PIT_CTRL_COUNT_BCD = 0x01	/* 4-decade BCD counter.  */

   };

-void EXPORT_FUNC(grub_pit_wait) (grub_uint16_t tics);

-

 #endif /* ! KERNEL_CPU_PIT_HEADER */

diff --git a/include/grub/i386/tsc.h b/include/grub/i386/tsc.h

index 2442d7e..d25d0e3 100644

--- a/include/grub/i386/tsc.h

+++ b/include/grub/i386/tsc.h

@@ -137,5 +137,7 @@ grub_cpu_is_tsc_supported (void)

 void grub_tsc_init (void);

 grub_uint64_t grub_tsc_get_time_ms (void);

+/* In ms per 2^32 ticks.  */

+extern grub_uint32_t EXPORT_VAR(grub_tsc_rate);

 #endif /* ! KERNEL_CPU_TSC_HEADER */

-- 

1.8.1.4