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