fbcvt.c

  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 size = 256;
218	int off = 0;
219	u8 *buf;
220
221	buf = kzalloc(size, GFP_KERNEL);
222	if (!buf)
223		return;
224
225	pixcount = (cvt->xres * (cvt->yres/cvt->interlace))/1000000;
226	pixcount_mod = (cvt->xres * (cvt->yres/cvt->interlace)) % 1000000;
227	pixcount_mod /= 1000;
228
229	off += scnprintf(buf + off, size - off, "fbcvt: %dx%d@%d: CVT Name - ",
230			    cvt->xres, cvt->yres, cvt->refresh);
231
232	if (cvt->status) {
233		off += scnprintf(buf + off, size - off,
234				 "Not a CVT standard - %d.%03d Mega Pixel Image\n",
235				 pixcount, pixcount_mod);
236	} else {
237		if (pixcount)
238			off += scnprintf(buf + off, size - off, "%d", pixcount);
239
240		off += scnprintf(buf + off, size - off, ".%03dM", pixcount_mod);
241
242		if (cvt->aspect_ratio == 0)
243			off += scnprintf(buf + off, size - off, "3");
244		else if (cvt->aspect_ratio == 3)
245			off += scnprintf(buf + off, size - off, "4");
246		else if (cvt->aspect_ratio == 1 || cvt->aspect_ratio == 4)
247			off += scnprintf(buf + off, size - off, "9");
248		else if (cvt->aspect_ratio == 2)
249			off += scnprintf(buf + off, size - off, "A");
250
251		if (cvt->flags & FB_CVT_FLAG_REDUCED_BLANK)
252			off += scnprintf(buf + off, size - off, "-R");
253	}
254
255	printk(KERN_INFO "%s\n", buf);
256	kfree(buf);
257}
258
259static void fb_cvt_convert_to_mode(struct fb_cvt_data *cvt,
260				   struct fb_videomode *mode)
261{
262	mode->refresh = cvt->f_refresh;
263	mode->pixclock = KHZ2PICOS(cvt->pixclock/1000);
264	mode->left_margin = cvt->h_back_porch;
265	mode->right_margin = cvt->h_front_porch;
266	mode->hsync_len = cvt->hsync;
267	mode->upper_margin = cvt->v_back_porch;
268	mode->lower_margin = cvt->v_front_porch;
269	mode->vsync_len = cvt->vsync;
270
271	mode->sync &= ~(FB_SYNC_HOR_HIGH_ACT | FB_SYNC_VERT_HIGH_ACT);
272
273	if (cvt->flags & FB_CVT_FLAG_REDUCED_BLANK)
274		mode->sync |= FB_SYNC_HOR_HIGH_ACT;
275	else
276		mode->sync |= FB_SYNC_VERT_HIGH_ACT;
277}
278
279/*
280 * fb_find_mode_cvt - calculate mode using VESA(TM) CVT
281 * @mode: pointer to fb_videomode; xres, yres, refresh and vmode must be
282 *        pre-filled with the desired values
283 * @margins: add margin to calculation (1.8% of xres and yres)
284 * @rb: compute with reduced blanking (for flatpanels)
285 *
286 * RETURNS:
287 * 0 for success
288 * @mode is filled with computed values.  If interlaced, the refresh field
289 * will be filled with the field rate (2x the frame rate)
290 *
291 * DESCRIPTION:
292 * Computes video timings using VESA(TM) Coordinated Video Timings
293 */
294int fb_find_mode_cvt(struct fb_videomode *mode, int margins, int rb)
295{
296	struct fb_cvt_data cvt;
297
298	memset(&cvt, 0, sizeof(cvt));
299
300	if (margins)
301	    cvt.flags |= FB_CVT_FLAG_MARGINS;
302
303	if (rb)
304	    cvt.flags |= FB_CVT_FLAG_REDUCED_BLANK;
305
306	if (mode->vmode & FB_VMODE_INTERLACED)
307	    cvt.flags |= FB_CVT_FLAG_INTERLACED;
308
309	cvt.xres = mode->xres;
310	cvt.yres = mode->yres;
311	cvt.refresh = mode->refresh;
312	cvt.f_refresh = cvt.refresh;
313	cvt.interlace = 1;
314
315	if (!cvt.xres || !cvt.yres || !cvt.refresh || cvt.f_refresh > INT_MAX) {
316		printk(KERN_INFO "fbcvt: Invalid input parameters\n");
317		return 1;
318	}
319
320	if (!(cvt.refresh == 50 || cvt.refresh == 60 || cvt.refresh == 70 ||
321	      cvt.refresh == 85)) {
322		printk(KERN_INFO "fbcvt: Refresh rate not CVT "
323		       "standard\n");
324		cvt.status = 1;
325	}
326
327	cvt.xres &= ~(FB_CVT_CELLSIZE - 1);
328
329	if (cvt.flags & FB_CVT_FLAG_INTERLACED) {
330		cvt.interlace = 2;
331		cvt.f_refresh *= 2;
332	}
333
334	if (cvt.flags & FB_CVT_FLAG_REDUCED_BLANK) {
335		if (cvt.refresh != 60) {
336			printk(KERN_INFO "fbcvt: 60Hz refresh rate "
337			       "advised for reduced blanking\n");
338			cvt.status = 1;
339		}
340	}
341
342	if (cvt.flags & FB_CVT_FLAG_MARGINS) {
343		cvt.h_margin = (cvt.xres * 18)/1000;
344		cvt.h_margin &= ~(FB_CVT_CELLSIZE - 1);
345		cvt.v_margin = ((cvt.yres/cvt.interlace)* 18)/1000;
346	}
347
348	cvt.aspect_ratio = fb_cvt_aspect_ratio(&cvt);
349	cvt.active_pixels = cvt.xres + 2 * cvt.h_margin;
350	cvt.hperiod = fb_cvt_hperiod(&cvt);
351	cvt.vsync = fb_cvt_vbi_tab[cvt.aspect_ratio];
352	cvt.vtotal = fb_cvt_vtotal(&cvt);
353	cvt.hblank = fb_cvt_hblank(&cvt);
354	cvt.htotal = cvt.active_pixels + cvt.hblank;
355	cvt.hsync = fb_cvt_hsync(&cvt);
356	cvt.pixclock = fb_cvt_pixclock(&cvt);
357	cvt.hfreq = cvt.pixclock/cvt.htotal;
358	cvt.h_back_porch = cvt.hblank/2 + cvt.h_margin;
359	cvt.h_front_porch = cvt.hblank - cvt.hsync - cvt.h_back_porch +
360		2 * cvt.h_margin;
361	cvt.v_front_porch = 3 + cvt.v_margin;
362	cvt.v_back_porch = cvt.vtotal - cvt.yres/cvt.interlace -
363	    cvt.v_front_porch - cvt.vsync;
364	fb_cvt_print_name(&cvt);
365	fb_cvt_convert_to_mode(&cvt, mode);
366
367	return 0;
368}