1/* Header:   //Mercury/Projects/archives/XFree86/4.0/smi_dac.c-arc   1.8   27 Nov 2000 15:47:08   Frido  $ */
2
3/*
4Copyright (C) 1994-1998 The XFree86 Project, Inc.  All Rights Reserved.
5Copyright (C) 2000 Silicon Motion, Inc.  All Rights Reserved.
6
7Permission is hereby granted, free of charge, to any person obtaining a copy of
8this software and associated documentation files (the "Software"), to deal in
9the Software without restriction, including without limitation the rights to
10use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
11of the Software, and to permit persons to whom the Software is furnished to do
12so, subject to the following conditions:
13
14The above copyright notice and this permission notice shall be included in all
15copies or substantial portions of the Software.
16
17THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
18IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FIT-
19NESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
20XFREE86 PROJECT BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
21AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
22WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
23
24Except as contained in this notice, the names of the XFree86 Project and
25Silicon Motion shall not be used in advertising or otherwise to promote the
26sale, use or other dealings in this Software without prior written
27authorization from the XFree86 Project and Silicon Motion.
28*/
29
30#ifdef HAVE_CONFIG_H
31#include "config.h"
32#endif
33
34#include "smi.h"
35
36#define BASE_FREQ	14.31818	/* MHz */
37
38void
39SMI_CommonCalcClock(int scrnIndex, long freq, int min_m, int min_n1,
40		    int max_n1, int min_n2, int max_n2, long freq_min,
41		    long freq_max, unsigned char *mdiv, unsigned char *ndiv)
42{
43    ScrnInfoPtr pScrn = xf86Screens[scrnIndex];
44    SMIPtr pSmi = SMIPTR(pScrn);
45    double div, diff, best_diff;
46    unsigned int m;
47    unsigned char n1, n2;
48    unsigned char best_n1 = 63, best_n2 = 3, best_m = 255;
49
50    double ffreq     = freq     / 1000.0 / BASE_FREQ;
51    double ffreq_min = freq_min / 1000.0 / BASE_FREQ;
52    double ffreq_max = freq_max / 1000.0 / BASE_FREQ;
53
54    if (ffreq < ffreq_min / (1 << max_n2)) {
55	xf86DrvMsg(scrnIndex,X_WARNING,"invalid frequency %1.3f MHz  [freq >= %1.3f MHz]\n",
56		ffreq * BASE_FREQ, ffreq_min * BASE_FREQ / (1 << max_n2));
57	ffreq = ffreq_min / (1 << max_n2);
58    }
59    if (ffreq > ffreq_max / (1 << min_n2)) {
60	xf86DrvMsg(scrnIndex,X_WARNING,"invalid frequency %1.3f MHz  [freq <= %1.3f MHz]\n",
61		ffreq * BASE_FREQ, ffreq_max * BASE_FREQ / (1 << min_n2));
62	ffreq = ffreq_max / (1 << min_n2);
63    }
64
65    /* work out suitable timings */
66    best_diff = ffreq;
67
68    for (n2 = min_n2; n2 <= max_n2; n2++) {
69	for (n1 = min_n1; n1 <= max_n1; n1++) {
70	    m = (int)(ffreq * n1 * (1 << n2) + 0.5);
71	    if ( (m < min_m) || (m > 255) ) {
72		continue;
73	    }
74	    div = (double)(m) / (double)(n1);
75	    if ( (div >= ffreq_min) && (div <= ffreq_max) ) {
76		diff = ffreq - div / (1 << n2);
77		if (diff < 0.0) {
78		    diff = -diff;
79		}
80		if (diff < best_diff) {
81		    best_diff = diff;
82		    best_m    = m;
83		    best_n1   = n1;
84		    best_n2   = n2;
85		}
86	    }
87	}
88    }
89
90    DEBUG("Clock parameters for %1.6f MHz: m=%d, n1=%d, n2=%d\n",
91	  ((double)(best_m) / (double)(best_n1) / (1 << best_n2)) * BASE_FREQ,
92	  best_m, best_n1, best_n2);
93
94    if (SMI_LYNX_SERIES(pSmi->Chipset)) {
95	/* Prefer post scalar enabled for even denominators */
96	if (freq < 70000 && max_n2 > 0 &&
97	    best_n2 == 0 && best_n1 % 2 == 0){
98	    best_n1 >>= 1;
99	    best_n2 = 1;
100	}
101
102	*ndiv = best_n1 |
103	    (best_n2 & 0x1) << 7 |
104	    (best_n2 & 0x2) >> 1 <<6;
105    } else {
106	*ndiv = best_n1 | (best_n2 << 7);
107
108	/* Enable second VCO */
109	if (freq > 120000)
110	    *ndiv |= 1 << 6;
111    }
112
113    *mdiv = best_m;
114}
115
116