linux/drivers/video/fbcvt.c
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   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_back_porch = 3 + cvt.v_margin;
 373        cvt.v_front_porch = cvt.vtotal - cvt.yres/cvt.interlace -
 374            cvt.v_back_porch - cvt.vsync;
 375        fb_cvt_print_name(&cvt);
 376        fb_cvt_convert_to_mode(&cvt, mode);
 377
 378        return 0;
 379}
 380
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