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
35struct 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
61static 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 */
73static 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 */
91static 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
101static 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
125static 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
138static 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
162static 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
172static 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
188static 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
214static 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
270static 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 */
305int 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_front_porch = 3 + cvt.v_margin;
373	cvt.v_back_porch = cvt.vtotal - cvt.yres/cvt.interlace -
374	    cvt.v_front_porch - cvt.vsync;
375	fb_cvt_print_name(&cvt);
376	fb_cvt_convert_to_mode(&cvt, mode);
377
378	return 0;
379}
380