129 lines
4.9 KiB
C
129 lines
4.9 KiB
C
/*
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* Copyright 1999 SuSE, Inc.
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*
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* Permission to use, copy, modify, distribute, and sell this software and its
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* documentation for any purpose is hereby granted without fee, provided that
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* the above copyright notice appear in all copies and that both that
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* copyright notice and this permission notice appear in supporting
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* documentation, and that the name of SuSE not be used in advertising or
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* publicity pertaining to distribution of the software without specific,
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* written prior permission. SuSE makes no representations about the
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* suitability of this software for any purpose. It is provided "as is"
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* without express or implied warranty.
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*
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* SuSE DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL SuSE
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* BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
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* OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
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* CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*
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* Author: Keith Packard, SuSE, Inc.
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*/
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/* $XFree86: xc/programs/Xserver/hw/tinyx/savage/s3clock.c,v 1.1 2004/06/02 22:43:02 dawes Exp $ */
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/*
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* Copyright (c) 2004 by The XFree86 Project, Inc.
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* All rights reserved.
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*
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* Permission is hereby granted, free of charge, to any person obtaining
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* a copy of this software and associated documentation files (the
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* "Software"), to deal in the Software without restriction, including
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* without limitation the rights to use, copy, modify, merge, publish,
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* distribute, sublicense, and/or sell copies of the Software, and to
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* permit persons to whom the Software is furnished to do so, subject
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* to the following conditions:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions, and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer
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* in the documentation and/or other materials provided with the
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* distribution, and in the same place and form as other copyright,
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* license and disclaimer information.
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*
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* 3. The end-user documentation included with the redistribution,
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* if any, must include the following acknowledgment: "This product
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* includes software developed by The XFree86 Project, Inc
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* (http://www.xfree86.org/) and its contributors", in the same
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* place and form as other third-party acknowledgments. Alternately,
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* this acknowledgment may appear in the software itself, in the
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* same form and location as other such third-party acknowledgments.
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*
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* 4. Except as contained in this notice, the name of The XFree86
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* Project, Inc shall not be used in advertising or otherwise to
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* promote the sale, use or other dealings in this Software without
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* prior written authorization from The XFree86 Project, Inc.
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*
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* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
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* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE XFREE86 PROJECT, INC OR ITS CONTRIBUTORS BE
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* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
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* OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
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* OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
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* BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
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* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
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* OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
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* EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "s3.h"
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/*
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* Clock synthesis:
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*
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* f_out = f_ref * ((M + 2) / ((N + 2) * (1 << R)))
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*
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* Constraints:
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*
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* 1. 135MHz <= f_ref * ((M + 2) / (N + 2)) <= 270 MHz
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* 2. N >= 1
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*
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* Vertical refresh rate = clock / ((hsize + hblank) * (vsize + vblank))
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* Horizontal refresh rate = clock / (hsize + hblank)
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*/
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/* all in kHz */
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void
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s3GetClock (int target, int *Mp, int *Np, int *Rp, int maxM, int maxN, int maxR, int minVco)
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{
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int M, N, R, bestM = 0, bestN = 0;
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int f_vco, f_out;
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int err, besterr;
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/*
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* Compute correct R value to keep VCO in range
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*/
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for (R = 0; R <= maxR; R++)
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{
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f_vco = target * (1 << R);
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if (f_vco >= minVco)
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break;
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}
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/* M = f_out / f_ref * ((N + 2) * (1 << R)); */
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besterr = target;
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for (N = 1; N <= maxN; N++)
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{
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M = ((target * (N + 2) * (1 << R) + (S3_CLOCK_REF/2)) + S3_CLOCK_REF/2) / S3_CLOCK_REF - 2;
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if (0 <= M && M <= maxM)
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{
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f_out = S3_CLOCK(M,N,R);
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err = target - f_out;
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if (err < 0)
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err = -err;
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if (err < besterr)
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{
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besterr = err;
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bestM = M;
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bestN = N;
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}
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}
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}
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*Mp = bestM;
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*Np = bestN;
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*Rp = R;
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}
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