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fbcvt.c
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1 /*
2  * linux/drivers/video/fbcvt.c - VESA(TM) Coordinated Video Timings
3  *
4  * Copyright (C) 2005 Antonino Daplas <[email protected]>
5  *
6  * Based from the VESA(TM) Coordinated Video Timing Generator by
7  * Graham Loveridge April 9, 2003 available at
8  * http://www.elo.utfsm.cl/~elo212/docs/CVTd6r1.xls
9  *
10  * This file is subject to the terms and conditions of the GNU General Public
11  * License. See the file COPYING in the main directory of this archive
12  * for more details.
13  *
14  */
15 #include <linux/fb.h>
16 #include <linux/slab.h>
17 
18 #define FB_CVT_CELLSIZE 8
19 #define FB_CVT_GTF_C 40
20 #define FB_CVT_GTF_J 20
21 #define FB_CVT_GTF_K 128
22 #define FB_CVT_GTF_M 600
23 #define FB_CVT_MIN_VSYNC_BP 550
24 #define FB_CVT_MIN_VPORCH 3
25 #define FB_CVT_MIN_BPORCH 6
26 
27 #define FB_CVT_RB_MIN_VBLANK 460
28 #define FB_CVT_RB_HBLANK 160
29 #define FB_CVT_RB_V_FPORCH 3
30 
31 #define FB_CVT_FLAG_REDUCED_BLANK 1
32 #define FB_CVT_FLAG_MARGINS 2
33 #define FB_CVT_FLAG_INTERLACED 4
34 
35 struct fb_cvt_data {
36  u32 xres;
37  u32 yres;
38  u32 refresh;
39  u32 f_refresh;
40  u32 pixclock;
41  u32 hperiod;
42  u32 hblank;
43  u32 hfreq;
44  u32 htotal;
45  u32 vtotal;
46  u32 vsync;
47  u32 hsync;
48  u32 h_front_porch;
49  u32 h_back_porch;
50  u32 v_front_porch;
51  u32 v_back_porch;
52  u32 h_margin;
53  u32 v_margin;
54  u32 interlace;
55  u32 aspect_ratio;
56  u32 active_pixels;
57  u32 flags;
58  u32 status;
59 };
60 
61 static const unsigned char fb_cvt_vbi_tab[] = {
62  4, /* 4:3 */
63  5, /* 16:9 */
64  6, /* 16:10 */
65  7, /* 5:4 */
66  7, /* 15:9 */
67  8, /* reserved */
68  9, /* reserved */
69  10 /* custom */
70 };
71 
72 /* returns hperiod * 1000 */
73 static u32 fb_cvt_hperiod(struct fb_cvt_data *cvt)
74 {
75  u32 num = 1000000000/cvt->f_refresh;
76  u32 den;
77 
78  if (cvt->flags & FB_CVT_FLAG_REDUCED_BLANK) {
79  num -= FB_CVT_RB_MIN_VBLANK * 1000;
80  den = 2 * (cvt->yres/cvt->interlace + 2 * cvt->v_margin);
81  } else {
82  num -= FB_CVT_MIN_VSYNC_BP * 1000;
83  den = 2 * (cvt->yres/cvt->interlace + cvt->v_margin * 2
84  + FB_CVT_MIN_VPORCH + cvt->interlace/2);
85  }
86 
87  return 2 * (num/den);
88 }
89 
90 /* returns ideal duty cycle * 1000 */
91 static u32 fb_cvt_ideal_duty_cycle(struct fb_cvt_data *cvt)
92 {
93  u32 c_prime = (FB_CVT_GTF_C - FB_CVT_GTF_J) *
94  (FB_CVT_GTF_K) + 256 * FB_CVT_GTF_J;
95  u32 m_prime = (FB_CVT_GTF_K * FB_CVT_GTF_M);
96  u32 h_period_est = cvt->hperiod;
97 
98  return (1000 * c_prime - ((m_prime * h_period_est)/1000))/256;
99 }
100 
101 static u32 fb_cvt_hblank(struct fb_cvt_data *cvt)
102 {
103  u32 hblank = 0;
104 
105  if (cvt->flags & FB_CVT_FLAG_REDUCED_BLANK)
106  hblank = FB_CVT_RB_HBLANK;
107  else {
108  u32 ideal_duty_cycle = fb_cvt_ideal_duty_cycle(cvt);
109  u32 active_pixels = cvt->active_pixels;
110 
111  if (ideal_duty_cycle < 20000)
112  hblank = (active_pixels * 20000)/
113  (100000 - 20000);
114  else {
115  hblank = (active_pixels * ideal_duty_cycle)/
116  (100000 - ideal_duty_cycle);
117  }
118  }
119 
120  hblank &= ~((2 * FB_CVT_CELLSIZE) - 1);
121 
122  return hblank;
123 }
124 
125 static u32 fb_cvt_hsync(struct fb_cvt_data *cvt)
126 {
127  u32 hsync;
128 
129  if (cvt->flags & FB_CVT_FLAG_REDUCED_BLANK)
130  hsync = 32;
131  else
132  hsync = (FB_CVT_CELLSIZE * cvt->htotal)/100;
133 
134  hsync &= ~(FB_CVT_CELLSIZE - 1);
135  return hsync;
136 }
137 
138 static u32 fb_cvt_vbi_lines(struct fb_cvt_data *cvt)
139 {
140  u32 vbi_lines, min_vbi_lines, act_vbi_lines;
141 
142  if (cvt->flags & FB_CVT_FLAG_REDUCED_BLANK) {
143  vbi_lines = (1000 * FB_CVT_RB_MIN_VBLANK)/cvt->hperiod + 1;
144  min_vbi_lines = FB_CVT_RB_V_FPORCH + cvt->vsync +
145  FB_CVT_MIN_BPORCH;
146 
147  } else {
148  vbi_lines = (FB_CVT_MIN_VSYNC_BP * 1000)/cvt->hperiod + 1 +
149  FB_CVT_MIN_VPORCH;
150  min_vbi_lines = cvt->vsync + FB_CVT_MIN_BPORCH +
151  FB_CVT_MIN_VPORCH;
152  }
153 
154  if (vbi_lines < min_vbi_lines)
155  act_vbi_lines = min_vbi_lines;
156  else
157  act_vbi_lines = vbi_lines;
158 
159  return act_vbi_lines;
160 }
161 
162 static u32 fb_cvt_vtotal(struct fb_cvt_data *cvt)
163 {
164  u32 vtotal = cvt->yres/cvt->interlace;
165 
166  vtotal += 2 * cvt->v_margin + cvt->interlace/2 + fb_cvt_vbi_lines(cvt);
167  vtotal |= cvt->interlace/2;
168 
169  return vtotal;
170 }
171 
172 static u32 fb_cvt_pixclock(struct fb_cvt_data *cvt)
173 {
174  u32 pixclock;
175 
176  if (cvt->flags & FB_CVT_FLAG_REDUCED_BLANK)
177  pixclock = (cvt->f_refresh * cvt->vtotal * cvt->htotal)/1000;
178  else
179  pixclock = (cvt->htotal * 1000000)/cvt->hperiod;
180 
181  pixclock /= 250;
182  pixclock *= 250;
183  pixclock *= 1000;
184 
185  return pixclock;
186 }
187 
188 static u32 fb_cvt_aspect_ratio(struct fb_cvt_data *cvt)
189 {
190  u32 xres = cvt->xres;
191  u32 yres = cvt->yres;
192  u32 aspect = -1;
193 
194  if (xres == (yres * 4)/3 && !((yres * 4) % 3))
195  aspect = 0;
196  else if (xres == (yres * 16)/9 && !((yres * 16) % 9))
197  aspect = 1;
198  else if (xres == (yres * 16)/10 && !((yres * 16) % 10))
199  aspect = 2;
200  else if (xres == (yres * 5)/4 && !((yres * 5) % 4))
201  aspect = 3;
202  else if (xres == (yres * 15)/9 && !((yres * 15) % 9))
203  aspect = 4;
204  else {
205  printk(KERN_INFO "fbcvt: Aspect ratio not CVT "
206  "standard\n");
207  aspect = 7;
208  cvt->status = 1;
209  }
210 
211  return aspect;
212 }
213 
214 static void fb_cvt_print_name(struct fb_cvt_data *cvt)
215 {
216  u32 pixcount, pixcount_mod;
217  int cnt = 255, offset = 0, read = 0;
218  u8 *buf = kzalloc(256, GFP_KERNEL);
219 
220  if (!buf)
221  return;
222 
223  pixcount = (cvt->xres * (cvt->yres/cvt->interlace))/1000000;
224  pixcount_mod = (cvt->xres * (cvt->yres/cvt->interlace)) % 1000000;
225  pixcount_mod /= 1000;
226 
227  read = snprintf(buf+offset, cnt, "fbcvt: %dx%d@%d: CVT Name - ",
228  cvt->xres, cvt->yres, cvt->refresh);
229  offset += read;
230  cnt -= read;
231 
232  if (cvt->status)
233  snprintf(buf+offset, cnt, "Not a CVT standard - %d.%03d Mega "
234  "Pixel Image\n", pixcount, pixcount_mod);
235  else {
236  if (pixcount) {
237  read = snprintf(buf+offset, cnt, "%d", pixcount);
238  cnt -= read;
239  offset += read;
240  }
241 
242  read = snprintf(buf+offset, cnt, ".%03dM", pixcount_mod);
243  cnt -= read;
244  offset += read;
245 
246  if (cvt->aspect_ratio == 0)
247  read = snprintf(buf+offset, cnt, "3");
248  else if (cvt->aspect_ratio == 3)
249  read = snprintf(buf+offset, cnt, "4");
250  else if (cvt->aspect_ratio == 1 || cvt->aspect_ratio == 4)
251  read = snprintf(buf+offset, cnt, "9");
252  else if (cvt->aspect_ratio == 2)
253  read = snprintf(buf+offset, cnt, "A");
254  else
255  read = 0;
256  cnt -= read;
257  offset += read;
258 
259  if (cvt->flags & FB_CVT_FLAG_REDUCED_BLANK) {
260  read = snprintf(buf+offset, cnt, "-R");
261  cnt -= read;
262  offset += read;
263  }
264  }
265 
266  printk(KERN_INFO "%s\n", buf);
267  kfree(buf);
268 }
269 
270 static void fb_cvt_convert_to_mode(struct fb_cvt_data *cvt,
271  struct fb_videomode *mode)
272 {
273  mode->refresh = cvt->f_refresh;
274  mode->pixclock = KHZ2PICOS(cvt->pixclock/1000);
275  mode->left_margin = cvt->h_back_porch;
276  mode->right_margin = cvt->h_front_porch;
277  mode->hsync_len = cvt->hsync;
278  mode->upper_margin = cvt->v_back_porch;
279  mode->lower_margin = cvt->v_front_porch;
280  mode->vsync_len = cvt->vsync;
281 
282  mode->sync &= ~(FB_SYNC_HOR_HIGH_ACT | FB_SYNC_VERT_HIGH_ACT);
283 
284  if (cvt->flags & FB_CVT_FLAG_REDUCED_BLANK)
285  mode->sync |= FB_SYNC_HOR_HIGH_ACT;
286  else
287  mode->sync |= FB_SYNC_VERT_HIGH_ACT;
288 }
289 
290 /*
291  * fb_find_mode_cvt - calculate mode using VESA(TM) CVT
292  * @mode: pointer to fb_videomode; xres, yres, refresh and vmode must be
293  * pre-filled with the desired values
294  * @margins: add margin to calculation (1.8% of xres and yres)
295  * @rb: compute with reduced blanking (for flatpanels)
296  *
297  * RETURNS:
298  * 0 for success
299  * @mode is filled with computed values. If interlaced, the refresh field
300  * will be filled with the field rate (2x the frame rate)
301  *
302  * DESCRIPTION:
303  * Computes video timings using VESA(TM) Coordinated Video Timings
304  */
305 int fb_find_mode_cvt(struct fb_videomode *mode, int margins, int rb)
306 {
307  struct fb_cvt_data cvt;
308 
309  memset(&cvt, 0, sizeof(cvt));
310 
311  if (margins)
312  cvt.flags |= FB_CVT_FLAG_MARGINS;
313 
314  if (rb)
315  cvt.flags |= FB_CVT_FLAG_REDUCED_BLANK;
316 
317  if (mode->vmode & FB_VMODE_INTERLACED)
318  cvt.flags |= FB_CVT_FLAG_INTERLACED;
319 
320  cvt.xres = mode->xres;
321  cvt.yres = mode->yres;
322  cvt.refresh = mode->refresh;
323  cvt.f_refresh = cvt.refresh;
324  cvt.interlace = 1;
325 
326  if (!cvt.xres || !cvt.yres || !cvt.refresh) {
327  printk(KERN_INFO "fbcvt: Invalid input parameters\n");
328  return 1;
329  }
330 
331  if (!(cvt.refresh == 50 || cvt.refresh == 60 || cvt.refresh == 70 ||
332  cvt.refresh == 85)) {
333  printk(KERN_INFO "fbcvt: Refresh rate not CVT "
334  "standard\n");
335  cvt.status = 1;
336  }
337 
338  cvt.xres &= ~(FB_CVT_CELLSIZE - 1);
339 
340  if (cvt.flags & FB_CVT_FLAG_INTERLACED) {
341  cvt.interlace = 2;
342  cvt.f_refresh *= 2;
343  }
344 
345  if (cvt.flags & FB_CVT_FLAG_REDUCED_BLANK) {
346  if (cvt.refresh != 60) {
347  printk(KERN_INFO "fbcvt: 60Hz refresh rate "
348  "advised for reduced blanking\n");
349  cvt.status = 1;
350  }
351  }
352 
353  if (cvt.flags & FB_CVT_FLAG_MARGINS) {
354  cvt.h_margin = (cvt.xres * 18)/1000;
355  cvt.h_margin &= ~(FB_CVT_CELLSIZE - 1);
356  cvt.v_margin = ((cvt.yres/cvt.interlace)* 18)/1000;
357  }
358 
359  cvt.aspect_ratio = fb_cvt_aspect_ratio(&cvt);
360  cvt.active_pixels = cvt.xres + 2 * cvt.h_margin;
361  cvt.hperiod = fb_cvt_hperiod(&cvt);
362  cvt.vsync = fb_cvt_vbi_tab[cvt.aspect_ratio];
363  cvt.vtotal = fb_cvt_vtotal(&cvt);
364  cvt.hblank = fb_cvt_hblank(&cvt);
365  cvt.htotal = cvt.active_pixels + cvt.hblank;
366  cvt.hsync = fb_cvt_hsync(&cvt);
367  cvt.pixclock = fb_cvt_pixclock(&cvt);
368  cvt.hfreq = cvt.pixclock/cvt.htotal;
369  cvt.h_back_porch = cvt.hblank/2 + cvt.h_margin;
370  cvt.h_front_porch = cvt.hblank - cvt.hsync - cvt.h_back_porch +
371  2 * cvt.h_margin;
372  cvt.v_back_porch = 3 + cvt.v_margin;
373  cvt.v_front_porch = cvt.vtotal - cvt.yres/cvt.interlace -
374  cvt.v_back_porch - cvt.vsync;
375  fb_cvt_print_name(&cvt);
376  fb_cvt_convert_to_mode(&cvt, mode);
377 
378  return 0;
379 }
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