1 /*
2  * linux/drivers/video/fbcvt.c - VESA(TM) Coordinated Video Timings
3  *
4  * Copyright (C) 2005 Antonino Daplas <adaplas@pol.net>
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 */
fb_cvt_hperiod(struct fb_cvt_data * cvt)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 */
fb_cvt_ideal_duty_cycle(struct fb_cvt_data * cvt)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 
fb_cvt_hblank(struct fb_cvt_data * cvt)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 
fb_cvt_hsync(struct fb_cvt_data * cvt)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 
fb_cvt_vbi_lines(struct fb_cvt_data * cvt)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 
fb_cvt_vtotal(struct fb_cvt_data * cvt)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 
fb_cvt_pixclock(struct fb_cvt_data * cvt)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 
fb_cvt_aspect_ratio(struct fb_cvt_data * cvt)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 
fb_cvt_print_name(struct fb_cvt_data * cvt)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 
fb_cvt_convert_to_mode(struct fb_cvt_data * cvt,struct fb_videomode * mode)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  */
fb_find_mode_cvt(struct fb_videomode * mode,int margins,int rb)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 }
380