/*====================================================================
 * aisetfreq.c
 *
 * Copyright 1995, Silicon Graphics, Inc.
 * All Rights Reserved.
 *
 * This is UNPUBLISHED PROPRIETARY SOURCE CODE of Silicon Graphics,
 * Inc.; the contents of this file may not be disclosed to third
 * parties, copied or duplicated in any form, in whole or in part,
 * without the prior written permission of Silicon Graphics, Inc.
 *
 * RESTRICTED RIGHTS LEGEND:
 * Use, duplication or disclosure by the Government is subject to
 * restrictions as set forth in subdivision (c)(1)(ii) of the Rights
 * in Technical Data and Computer Software clause at DFARS
 * 252.227-7013, and/or in similar or successor clauses in the FAR,
 * DOD or NASA FAR Supplement. Unpublished - rights reserved under the
 * Copyright Laws of the United States.
 *====================================================================*/

/**************************************************************************
 *
 *  $Revision: 1.1.1.2 $
 *  $Date: 2002/10/29 08:06:43 $
 *  $Source: /root/leakn64/depot/rf/sw/n64os20l/libultra/monegi/ai/aisetfreq.c,v $
 *
 **************************************************************************/

#include "osint.h"
#include "rcp.h"
#include "assert.h"


extern int osViClock;


/*
 * Name:   osAiSetFrequency
 *
 * Description:
 *	Based on the input frequency, calculate the corresponding values for
 *	the two internal divisors. 
 *
 *	Upon completion, return the nearest frequency that the divisors can 
 *	generate. If the requested frequency is not within allowable range, 
 *	return a "-1".
 *
 * Globals Referenced: 
 *	osViClock (vi.c) 	- video clock frequency in Hz (either
 *				  VI_NTSC_CLOCK or VI_PAL_CLOCK)
 */
s32
osAiSetFrequency(u32 frequency)
{

    register unsigned int  dacRate;
    register unsigned char bitRate;
    register float f;    

    /* Based on frequency, find the corresponding values for DAC rate and 
     * BIT rate registers. Also, return the closest frequency to caller.
     */

#ifdef _DEBUG
     /* Check for valid AI frequency range based on video clock */
    if (osViClock == VI_PAL_CLOCK) {
        if ((frequency < AI_PAL_MIN_FREQ) || (frequency > AI_PAL_MAX_FREQ)) {
	    __osError(ERR_OSAISETFREQUENCY, 3,
		      AI_PAL_MIN_FREQ, AI_PAL_MAX_FREQ, frequency);
            return(-1);
	}
    }
    else if (osViClock == VI_MPAL_CLOCK) {
        if ((frequency < AI_MPAL_MIN_FREQ) || (frequency > AI_MPAL_MAX_FREQ)) {
	    __osError(ERR_OSAISETFREQUENCY, 3,
		      AI_MPAL_MIN_FREQ, AI_MPAL_MAX_FREQ, frequency);
            return(-1);
	}
    }
    else { /* Assume that it's NTSC */
        if ((frequency < AI_NTSC_MIN_FREQ) || (frequency > AI_NTSC_MAX_FREQ)) {
	    __osError(ERR_OSAISETFREQUENCY, 3,
		      AI_NTSC_MIN_FREQ, AI_NTSC_MAX_FREQ, frequency);
            return(-1);
	}
    }
#endif

    f = ((float)osViClock / (float)frequency) + 0.5F;  /* Rounding up */
    dacRate = (unsigned int)f;

    if (dacRate < AI_MIN_DAC_RATE)
        return(-1);

    /* if bitRate is 0, abus clock stops */
    bitRate = (unsigned char)(dacRate / 66);  

    if (bitRate > AI_MAX_BIT_RATE)
        bitRate = AI_MAX_BIT_RATE;

    IO_WRITE(AI_DACRATE_REG, dacRate-1);
    IO_WRITE(AI_BITRATE_REG, bitRate-1);

    /* Return the closest frequency */
    return((s32)((s32)osViClock/(s32)dacRate));  

}  /* osAiSetFrequency */