/*
 * ReactOS kernel
 * Copyright (C) 2000 David Welch <welch@cwcom.net>
 * Copyright (C) 1999 Gareth Owen <gaz@athene.co.uk>, Ramon von Handel
 * Copyright (C) 1991, 1992 Linus Torvalds
 * 
 * This software 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 2 of the
 * License, or (at your option) any later version.
 *
 * This software 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 this software; see the file COPYING. If not, write
 * to the Free Software Foundation, Inc., 675 Mass Ave, Cambridge,
 * MA 02139, USA.  
 *
 */
/* $Id$
 *
 * PROJECT:        ReactOS kernel
 * FILE:           ntoskrnl/hal/x86/udelay.c
 * PURPOSE:        Busy waiting
 * PROGRAMMER:     David Welch (david.welch@seh.ox.ac.uk)
 * UPDATE HISTORY:
 *                 06/11/99 Created
 */

/* INCLUDES ***************************************************************/

#include <ddk/ntddk.h>

#define NDEBUG
#include <internal/debug.h>

/* GLOBALS ******************************************************************/

static unsigned int delay_count = 1;

#define MILLISEC     (10)
#define FREQ         (1000/MILLISEC)

#define PRECISION    (8)

#define 	TMR_CTRL	0x43	/*	I/O for control		*/
#define		TMR_CNT0	0x40	/*	I/O for counter 0	*/
#define		TMR_CNT1	0x41	/*	I/O for counter 1	*/
#define		TMR_CNT2	0x42	/*	I/O for counter 2	*/

#define		TMR_SC0		0	/*	Select channel 0 	*/
#define		TMR_SC1		0x40	/*	Select channel 1 	*/
#define		TMR_SC2		0x80	/*	Select channel 2 	*/

#define		TMR_LOW		0x10	/*	RW low byte only 	*/
#define		TMR_HIGH	0x20	/*	RW high byte only 	*/
#define		TMR_BOTH	0x30	/*	RW both bytes 		*/

#define		TMR_MD0		0	/*	Mode 0 			*/
#define		TMR_MD1		0x2	/*	Mode 1 			*/
#define		TMR_MD2		0x4	/*	Mode 2 			*/
#define		TMR_MD3		0x6	/*	Mode 3 			*/
#define		TMR_MD4		0x8	/*	Mode 4 			*/
#define		TMR_MD5		0xA	/*	Mode 5 			*/

#define		TMR_BCD		1	/*	BCD mode 		*/

#define		TMR_LATCH	0	/*	Latch command 		*/

#define		TMR_READ	0xF0	/*    Read command 		*/
#define		TMR_CNT		0x20	/*    CNT bit  (Active low, subtract it) */
#define		TMR_STAT	0x10	/*    Status bit  (Active low, subtract it) */
#define		TMR_CH2		0x8	/*    Channel 2 bit 		*/
#define		TMR_CH1		0x4	/*    Channel 1 bit 		*/
#define		TMR_CH0		0x2	/*    Channel 0 bit 		*/

static BOOLEAN UdelayCalibrated = FALSE;

/* FUNCTIONS **************************************************************/

void init_pit(float h, unsigned char channel)
{
	unsigned int temp=0;
	
	temp = 1193180/h;
	
//	WRITE_PORT_UCHAR((PUCHAR)TMR_CTRL, 
//			 (channel*0x40) + TMR_BOTH + TMR_MD3);
        WRITE_PORT_UCHAR((PUCHAR)TMR_CTRL,
			 (channel*0x40) + TMR_BOTH + TMR_MD2);
	WRITE_PORT_UCHAR((PUCHAR)(0x40+channel), 
			 (unsigned char) temp);
	WRITE_PORT_UCHAR((PUCHAR)(0x40+channel), 
			 (unsigned char) (temp>>8));
}

VOID STDCALL
__KeStallExecutionProcessor(ULONG Loops)
{
   register unsigned int i;
   for (i=0; i<Loops;i++);
}

VOID STDCALL KeStallExecutionProcessor(ULONG Microseconds)
{
   __KeStallExecutionProcessor((delay_count*Microseconds)/1000);
}

#define HZ (100)
#define CLOCK_TICK_RATE (1193182)
#define LATCH (CLOCK_TICK_RATE / HZ)

static ULONG Read8254Timer(VOID)
{
	ULONG Count;

	WRITE_PORT_UCHAR((PUCHAR)0x43, 0x00);
	Count = READ_PORT_UCHAR((PUCHAR)0x40);
	Count |= READ_PORT_UCHAR((PUCHAR)0x40) << 8;
	return Count;
}


static VOID WaitFor8254Wraparound(VOID)
{
	ULONG CurCount, PrevCount = ~0;
	LONG Delta;

	CurCount = Read8254Timer();

	do {
		PrevCount = CurCount;
		CurCount = Read8254Timer();
		Delta = CurCount - PrevCount;

	/*
	 * This limit for delta seems arbitrary, but it isn't, it's
	 * slightly above the level of error a buggy Mercury/Neptune
	 * chipset timer can cause.
	 */

	} while (Delta < 300);
}

VOID HalpCalibrateStallExecution(VOID)
{
   ULONG i;
   ULONG calib_bit;
	 ULONG CurCount;

   if (UdelayCalibrated)
      return;

   UdelayCalibrated = TRUE;

   DbgPrint("Calibrating delay loop... [");

   /* Initialise timer interrupt with MILLISECOND ms interval        */
   WRITE_PORT_UCHAR((PUCHAR)0x43, 0x34);  /* binary, mode 2, LSB/MSB, ch 0 */
   WRITE_PORT_UCHAR((PUCHAR)0x40, LATCH & 0xff); /* LSB */
   WRITE_PORT_UCHAR((PUCHAR)0x40, LATCH >> 8); /* MSB */

   /* Stage 1:  Coarse calibration                                   */

   WaitFor8254Wraparound();

   delay_count = 1;

   do {
      delay_count <<= 1;                  /* Next delay count to try */

      WaitFor8254Wraparound();

      __KeStallExecutionProcessor(delay_count);      /* Do the delay */

	    CurCount = Read8254Timer();
   } while (CurCount > LATCH / 2);

   delay_count >>= 1;              /* Get bottom value for delay     */

   /* Stage 2:  Fine calibration                                     */
   DbgPrint("delay_count: %d", delay_count);

   calib_bit = delay_count;        /* Which bit are we going to test */

   for(i=0;i<PRECISION;i++) {
      calib_bit >>= 1;             /* Next bit to calibrate          */
      if(!calib_bit) break;        /* If we have done all bits, stop */

      delay_count |= calib_bit;        /* Set the bit in delay_count */

      WaitFor8254Wraparound();

      __KeStallExecutionProcessor(delay_count);      /* Do the delay */

      CurCount = Read8254Timer();
      if (CurCount <= LATCH / 2)   /* If a tick has passed, turn the */
        delay_count &= ~calib_bit; /* calibrated bit back off        */
   }

   /* We're finished:  Do the finishing touches                      */

   delay_count /= (MILLISEC / 2);   /* Calculate delay_count for 1ms */

   DbgPrint("]\n");
   DbgPrint("delay_count: %d\n", delay_count);
   DbgPrint("CPU speed: %d\n", delay_count/250);
#if 0
   DbgPrint("About to start delay loop test\n");
   DbgPrint("Waiting for five minutes...");
   for (i = 0; i < (5*60*1000*20); i++)
     {
	KeStallExecutionProcessor(50);
     }
   DbgPrint("finished\n");
   for(;;);
#endif
}

/* EOF */