root/drivers/video/fbdev/core/fbcvt.c

DEFINITIONS

1. fb_cvt_hperiod
2. fb_cvt_ideal_duty_cycle
3. fb_cvt_hblank
4. fb_cvt_hsync
5. fb_cvt_vbi_lines
6. fb_cvt_vtotal
7. fb_cvt_pixclock
8. fb_cvt_aspect_ratio
9. fb_cvt_print_name
10. fb_cvt_convert_to_mode
11. fb_find_mode_cvt

   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 */
  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_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 }