From a410b6abe3e2962de448dc0dc78179d520fa54f6 Mon Sep 17 00:00:00 2001
From: "Sergey Semyonov (Serge)" <ion2@mail.ru>
Date: Fri, 4 Sep 2015 11:50:27 +0000
Subject: [PATCH] Kernel: use 22.10 fixed point arithmetic in HPET timestamp
 calculation.

git-svn-id: svn://kolibrios.org@5791 a494cfbc-eb01-0410-851d-a64ba20cac60
---
 kernel/trunk/core/apic.inc | 22 ++++++++++++++++------
 kernel/trunk/init.inc      | 10 ++++++----
 2 files changed, 22 insertions(+), 10 deletions(-)

diff --git a/kernel/trunk/core/apic.inc b/kernel/trunk/core/apic.inc
index ef00f1429..0f215b3af 100644
--- a/kernel/trunk/core/apic.inc
+++ b/kernel/trunk/core/apic.inc
@@ -447,6 +447,7 @@ get_clock_ns:
         jz      .old_tics
 
         push    ebx
+        push    esi
         pushfd
         cli
 
@@ -456,15 +457,24 @@ get_clock_ns:
         mov     eax, [ebx+0xF0]
         mov     ecx, [ebx+0xF4]
         cmp     ecx, edx
-        jnz     @B
+        jne     @B
 
-        mov     ecx, [hpet_period]
-        mov     ebx, edx
-        imul    ebx, ecx
-        mul     ecx
-        add     edx, ebx
+        mul     [hpet_period]
+        shrd    eax, edx, 10
+        shr     edx, 10
+
+        mov     ebx, eax
+        mov     esi, edx
+
+        mov     eax, ecx
+        mul     [hpet_period]
+        shld    edx, eax, 22
+        shl     eax, 22
+        add     eax, ebx
+        adc     edx, esi
 
         popfd
+        pop     esi
         pop     ebx
         ret
 
diff --git a/kernel/trunk/init.inc b/kernel/trunk/init.inc
index de3b09cc4..a60e1eb0b 100644
--- a/kernel/trunk/init.inc
+++ b/kernel/trunk/init.inc
@@ -623,10 +623,12 @@ init_hpet:
         mov     ecx, eax
 
         mov     eax, [ebx+HPET_PERIOD]
-        mov     edx, 0x431BDE83
-        mul     edx
-        shr     edx, 18
-        mov     [hpet_period-OS_BASE], edx
+        xor     edx, edx
+        shld    edx, eax, 10
+        shl     eax, 10
+        mov     esi, 1000000
+        div     esi
+        mov     [hpet_period-OS_BASE], eax
 
         mov     esi, [ebx+HPET_CFG]
         and     esi, not HPET_CFG_ENABLE