drivers/video/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.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
  34 struct 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
  60 static 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 */
  72 static 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 */
  90 static 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
 100 static 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
 124 static 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
 137 static 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
 161 static 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
 171 static 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
 187 static 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
 213 static 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
 269 static 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  */
 304 int 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 }