1
2/*
3Copyright (C) 1994-1998 The XFree86 Project, Inc.  All Rights Reserved.
4
5Permission is hereby granted, free of charge, to any person obtaining a copy of
6this software and associated documentation files (the "Software"), to deal in
7the Software without restriction, including without limitation the rights to
8use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
9of the Software, and to permit persons to whom the Software is furnished to do
10so, subject to the following conditions:
11
12The above copyright notice and this permission notice shall be included in all
13copies or substantial portions of the Software.
14
15THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FIT-
17NESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
18XFREE86 PROJECT BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
19AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
20WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
21
22Except as contained in this notice, the name of the XFree86 Project shall not
23be used in advertising or otherwise to promote the sale, use or other dealings
24in this Software without prior written authorization from the XFree86 Project.
25*/
26
27/*
28 * s3v_dac.c
29 * Port to 4.0 design level
30 *
31 * S3 ViRGE driver
32 *
33 *
34 * s3vcommonCalcClock from S3gendac.c in pre 4.0 tree.
35 *
36 */
37
38#ifdef HAVE_CONFIG_H
39#include "config.h"
40#endif
41
42#include	"s3v.h"
43
44
45#define BASE_FREQ         14.31818   /* MHz */
46
47
48	/* function */
49void
50S3VCommonCalcClock(ScrnInfoPtr pScrn, DisplayModePtr mode,
51		   long freq, int min_m, int min_n1,
52		   int max_n1, int min_n2, int max_n2,
53		   long freq_min, long freq_max,
54		   unsigned char * mdiv, unsigned char * ndiv)
55{
56   double ffreq, ffreq_min, ffreq_max, ffreq_min_warn;
57   double div, diff, best_diff;
58   unsigned int m;
59   unsigned char n1, n2;
60   unsigned char best_n1=16+2, best_n2=2, best_m=125+2;
61
62   ffreq     = freq     / 1000.0 / BASE_FREQ;
63   ffreq_min = freq_min / 1000.0 / BASE_FREQ;
64   ffreq_max = freq_max / 1000.0 / BASE_FREQ;
65
66   /* Doublescan modes can run at half the min frequency */
67   /* But only use that value for warning and changing */
68   /* ffreq, don't change the actual min used for clock calcs below. */
69   if(mode->Flags & V_DBLSCAN && ffreq_min)
70     ffreq_min_warn = ffreq_min / 2;
71   else
72     ffreq_min_warn = ffreq_min;
73
74   if (ffreq < ffreq_min_warn / (1<<max_n2)) {
75      xf86DrvMsg(pScrn->scrnIndex, X_ERROR,
76		 "invalid frequency %1.3f MHz  [freq <= %1.3f MHz]\n",
77		 ffreq*BASE_FREQ, ffreq_min_warn*BASE_FREQ / (1<<max_n2));
78      ffreq = ffreq_min_warn / (1<<max_n2);
79   }
80   if (ffreq > ffreq_max / (1<<min_n2)) {
81      xf86DrvMsg(pScrn->scrnIndex, X_ERROR,
82		 "invalid frequency %1.3f MHz  [freq >= %1.3f MHz]\n",
83		 ffreq*BASE_FREQ, ffreq_max*BASE_FREQ / (1<<min_n2));
84      ffreq = ffreq_max / (1<<min_n2);
85   }
86
87   /* work out suitable timings */
88
89   best_diff = ffreq;
90
91   for (n2=min_n2; n2<=max_n2; n2++) {
92      for (n1 = min_n1+2; n1 <= max_n1+2; n1++) {
93	 m = (int)(ffreq * n1 * (1<<n2) + 0.5) ;
94	 if (m < min_m+2 || m > 127+2)
95	    continue;
96	 div = (double)(m) / (double)(n1);
97	 if ((div >= ffreq_min) &&
98	     (div <= ffreq_max)) {
99	    diff = ffreq - div / (1<<n2);
100	    if (diff < 0.0)
101	       diff = -diff;
102	    if (diff < best_diff) {
103	       best_diff = diff;
104	       best_m    = m;
105	       best_n1   = n1;
106	       best_n2   = n2;
107	    }
108	 }
109      }
110   }
111
112#ifdef EXTENDED_DEBUG
113   ErrorF("Clock parameters for %1.6f MHz: m=%d, n1=%d, n2=%d\n",
114	  ((double)(best_m) / (double)(best_n1) / (1 << best_n2)) * BASE_FREQ,
115	  best_m-2, best_n1-2, best_n2);
116#endif
117
118   if (max_n1 == 63)
119      *ndiv = (best_n1 - 2) | (best_n2 << 6);
120   else
121      *ndiv = (best_n1 - 2) | (best_n2 << 5);
122   *mdiv = best_m - 2;
123}
124
125