1 /* $NetBSD: vesagtf.c,v 1.2 2013/09/15 15:56:07 martin Exp $ */
5 * Copyright (c) 2006 Itronix Inc.
8 * Written by Garrett D'Amore for Itronix Inc.
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 * 3. The name of Itronix Inc. may not be used to endorse
19 * or promote products derived from this software without specific
20 * prior written permission.
22 * THIS SOFTWARE IS PROVIDED BY ITRONIX INC. ``AS IS'' AND ANY EXPRESS
23 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
24 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED. IN NO EVENT SHALL ITRONIX INC. BE LIABLE FOR ANY
26 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
28 * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
29 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
30 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
31 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
32 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
36 * This was derived from a userland GTF program supplied by NVIDIA.
37 * NVIDIA's original boilerplate follows.
39 * Note that I have heavily modified the program for use in the EDID
40 * kernel code for NetBSD, including removing the use of floating
41 * point operations and making significant adjustments to minimize
42 * error propagation while operating with integer only math.
44 * This has required the use of 64-bit integers in a few places, but
45 * the upshot is that for a calculation of 1920x1200x85 (as an
46 * example), the error deviates by only ~.004% relative to the
47 * floating point version. This error is *well* within VESA
52 * Copyright (c) 2001, Andy Ritger aritger@nvidia.com
53 * All rights reserved.
55 * Redistribution and use in source and binary forms, with or without
56 * modification, are permitted provided that the following conditions
59 * o Redistributions of source code must retain the above copyright
60 * notice, this list of conditions and the following disclaimer.
61 * o Redistributions in binary form must reproduce the above copyright
62 * notice, this list of conditions and the following disclaimer
63 * in the documentation and/or other materials provided with the
65 * o Neither the name of NVIDIA nor the names of its contributors
66 * may be used to endorse or promote products derived from this
67 * software without specific prior written permission.
70 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
71 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT
72 * NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
73 * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
74 * THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
75 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
76 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
77 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
78 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
79 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
80 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
81 * POSSIBILITY OF SUCH DAMAGE.
85 * This program is based on the Generalized Timing Formula(GTF TM)
86 * Standard Version: 1.0, Revision: 1.0
88 * The GTF Document contains the following Copyright information:
90 * Copyright (c) 1994, 1995, 1996 - Video Electronics Standards
91 * Association. Duplication of this document within VESA member
92 * companies for review purposes is permitted. All other rights
95 * While every precaution has been taken in the preparation
96 * of this standard, the Video Electronics Standards Association and
97 * its contributors assume no responsibility for errors or omissions,
98 * and make no warranties, expressed or implied, of functionality
99 * of suitability for any purpose. The sample code contained within
100 * this standard may be used without restriction.
104 * The GTF EXCEL(TM) SPREADSHEET, a sample (and the definitive)
105 * implementation of the GTF Timing Standard, is available at:
107 * ftp://ftp.vesa.org/pub/GTF/GTF_V1R1.xls
111 * This program takes a desired resolution and vertical refresh rate,
112 * and computes mode timings according to the GTF Timing Standard.
113 * These mode timings can then be formatted as an XFree86 modeline
114 * or a mode description for use by fbset(8).
120 * The GTF allows for computation of "margins" (the visible border
121 * surrounding the addressable video); on most non-overscan type
122 * systems, the margin period is zero. I've implemented the margin
123 * computations but not enabled it because 1) I don't really have
124 * any experience with this, and 2) neither XFree86 modelines nor
125 * fbset fb.modes provide an obvious way for margin timings to be
126 * included in their mode descriptions (needs more investigation).
128 * The GTF provides for computation of interlaced mode timings;
129 * I've implemented the computations but not enabled them, yet.
130 * I should probably enable and test this at some point.
136 * o Add support for interlaced modes.
138 * o Implement the other portions of the GTF: compute mode timings
139 * given either the desired pixel clock or the desired horizontal
142 * o It would be nice if this were more general purpose to do things
143 * outside the scope of the GTF: like generate double scan mode
144 * timings, for example.
146 * o Printing digits to the right of the decimal point when the
147 * digits are 0 annoys me.
155 #include <sys/cdefs.h>
157 __FBSDID("$FreeBSD$");
158 #include <sys/types.h>
159 #include <sys/param.h>
160 #include <sys/systm.h>
161 #include <dev/videomode/videomode.h>
162 #include <dev/videomode/vesagtf.h>
166 #include <sys/types.h>
167 #include "videomode.h"
170 void print_xf86_mode(struct videomode *m);
173 #define CELL_GRAN 8 /* assumed character cell granularity */
175 /* C' and M' are part of the Blanking Duty Cycle computation */
177 * #define C_PRIME (((C - J) * K/256.0) + J)
178 * #define M_PRIME (K/256.0 * M)
182 * C' and M' multiplied by 256 to give integer math. Make sure to
183 * scale results using these back down, appropriately.
185 #define C_PRIME256(p) (((p->C - p->J) * p->K) + (p->J * 256))
186 #define M_PRIME256(p) (p->K * p->M)
188 #define DIVIDE(x,y) (((x) + ((y) / 2)) / (y))
191 * print_value() - print the result of the named computation; this is
192 * useful when comparing against the GTF EXCEL spreadsheet.
198 print_value(int n, const char *name, unsigned val)
200 printf("%2d: %-27s: %u\n", n, name, val);
203 #define print_value(n, name, val)
208 * vert_refresh() - as defined by the GTF Timing Standard, compute the
209 * Stage 1 Parameters using the vertical refresh frequency. In other
210 * words: input a desired resolution and desired refresh rate, and
211 * output the GTF mode timings.
213 * XXX All the code is in place to compute interlaced modes, but I don't
214 * feel like testing it right now.
216 * XXX margin computations are implemented but not tested (nor used by
217 * XFree86 of fbset mode descriptions, from what I can tell).
221 vesagtf_mode_params(unsigned h_pixels, unsigned v_lines, unsigned freq,
222 struct vesagtf_params *params, int flags, struct videomode *vmp)
224 unsigned v_field_rqd;
226 unsigned bottom_margin;
228 uint64_t h_period_est;
229 unsigned vsync_plus_bp;
230 unsigned v_back_porch __unused;
231 unsigned total_v_lines;
232 uint64_t v_field_est;
234 unsigned v_field_rate;
235 unsigned v_frame_rate __unused;
236 unsigned left_margin;
237 unsigned right_margin;
238 unsigned total_active_pixels;
239 uint64_t ideal_duty_cycle;
241 unsigned total_pixels;
245 unsigned h_front_porch;
246 unsigned v_odd_front_porch_lines;
252 /* 1. In order to give correct results, the number of horizontal
253 * pixels requested is first processed to ensure that it is divisible
254 * by the character size, by rounding it to the nearest character
257 * [H PIXELS RND] = ((ROUND([H PIXELS]/[CELL GRAN RND],0))*[CELLGRAN RND])
260 h_pixels = DIVIDE(h_pixels, CELL_GRAN) * CELL_GRAN;
262 print_value(1, "[H PIXELS RND]", h_pixels);
265 /* 2. If interlace is requested, the number of vertical lines assumed
266 * by the calculation must be halved, as the computation calculates
267 * the number of vertical lines per field. In either case, the
268 * number of lines is rounded to the nearest integer.
270 * [V LINES RND] = IF([INT RQD?]="y", ROUND([V LINES]/2,0),
271 * ROUND([V LINES],0))
274 v_lines = (flags & VESAGTF_FLAG_ILACE) ? DIVIDE(v_lines, 2) : v_lines;
276 print_value(2, "[V LINES RND]", v_lines);
279 /* 3. Find the frame rate required:
281 * [V FIELD RATE RQD] = IF([INT RQD?]="y", [I/P FREQ RQD]*2,
285 v_field_rqd = (flags & VESAGTF_FLAG_ILACE) ? (freq * 2) : (freq);
287 print_value(3, "[V FIELD RATE RQD]", v_field_rqd);
290 /* 4. Find number of lines in Top margin:
291 * 5. Find number of lines in Bottom margin:
293 * [TOP MARGIN (LINES)] = IF([MARGINS RQD?]="Y",
294 * ROUND(([MARGIN%]/100*[V LINES RND]),0),
297 * Ditto for bottom margin. Note that instead of %, we use PPT, which
298 * is parts per thousand. This helps us with integer math.
301 top_margin = bottom_margin = (flags & VESAGTF_FLAG_MARGINS) ?
302 DIVIDE(v_lines * params->margin_ppt, 1000) : 0;
304 print_value(4, "[TOP MARGIN (LINES)]", top_margin);
305 print_value(5, "[BOT MARGIN (LINES)]", bottom_margin);
308 /* 6. If interlace is required, then set variable [INTERLACE]=0.5:
310 * [INTERLACE]=(IF([INT RQD?]="y",0.5,0))
312 * To make this integer friendly, we use some special hacks in step
313 * 7 below. Please read those comments to understand why I am using
314 * a whole number of 1.0 instead of 0.5 here.
316 interlace = (flags & VESAGTF_FLAG_ILACE) ? 1 : 0;
318 print_value(6, "[2*INTERLACE]", interlace);
321 /* 7. Estimate the Horizontal period
323 * [H PERIOD EST] = ((1/[V FIELD RATE RQD]) - [MIN VSYNC+BP]/1000000) /
324 * ([V LINES RND] + (2*[TOP MARGIN (LINES)]) +
325 * [MIN PORCH RND]+[INTERLACE]) * 1000000
327 * To make it integer friendly, we pre-multiply the 1000000 to get to
328 * usec. This gives us:
330 * [H PERIOD EST] = ((1000000/[V FIELD RATE RQD]) - [MIN VSYNC+BP]) /
331 * ([V LINES RND] + (2 * [TOP MARGIN (LINES)]) +
332 * [MIN PORCH RND]+[INTERLACE])
334 * The other problem is that the interlace value is wrong. To get
335 * the interlace to a whole number, we multiply both the numerator and
336 * divisor by 2, so we can use a value of either 1 or 0 for the interlace
341 * [H PERIOD EST] = ((2*((1000000/[V FIELD RATE RQD]) - [MIN VSYNC+BP])) /
342 * (2*([V LINES RND] + (2*[TOP MARGIN (LINES)]) +
343 * [MIN PORCH RND]) + [2*INTERLACE]))
345 * Finally we multiply by another 1000, to get value in picosec.
346 * Why picosec? To minimize rounding errors. Gotta love integer
347 * math and error propagation.
350 h_period_est = DIVIDE(((DIVIDE(2000000000000ULL, v_field_rqd)) -
351 (2000000 * params->min_vsbp)),
352 ((2 * (v_lines + (2 * top_margin) + params->min_porch)) + interlace));
354 print_value(7, "[H PERIOD EST (ps)]", h_period_est);
357 /* 8. Find the number of lines in V sync + back porch:
359 * [V SYNC+BP] = ROUND(([MIN VSYNC+BP]/[H PERIOD EST]),0)
361 * But recall that h_period_est is in psec. So multiply by 1000000.
364 vsync_plus_bp = DIVIDE(params->min_vsbp * 1000000, h_period_est);
366 print_value(8, "[V SYNC+BP]", vsync_plus_bp);
369 /* 9. Find the number of lines in V back porch alone:
371 * [V BACK PORCH] = [V SYNC+BP] - [V SYNC RND]
373 * XXX is "[V SYNC RND]" a typo? should be [V SYNC RQD]?
376 v_back_porch = vsync_plus_bp - params->vsync_rqd;
378 print_value(9, "[V BACK PORCH]", v_back_porch);
381 /* 10. Find the total number of lines in Vertical field period:
383 * [TOTAL V LINES] = [V LINES RND] + [TOP MARGIN (LINES)] +
384 * [BOT MARGIN (LINES)] + [V SYNC+BP] + [INTERLACE] +
388 total_v_lines = v_lines + top_margin + bottom_margin + vsync_plus_bp +
389 interlace + params->min_porch;
391 print_value(10, "[TOTAL V LINES]", total_v_lines);
394 /* 11. Estimate the Vertical field frequency:
396 * [V FIELD RATE EST] = 1 / [H PERIOD EST] / [TOTAL V LINES] * 1000000
398 * Again, we want to pre multiply by 10^9 to convert for nsec, thereby
399 * making it usable in integer math.
403 * [V FIELD RATE EST] = 1000000000 / [H PERIOD EST] / [TOTAL V LINES]
405 * This is all scaled to get the result in uHz. Again, we're trying to
406 * minimize error propagation.
408 v_field_est = DIVIDE(DIVIDE(1000000000000000ULL, h_period_est),
411 print_value(11, "[V FIELD RATE EST(uHz)]", v_field_est);
414 /* 12. Find the actual horizontal period:
416 * [H PERIOD] = [H PERIOD EST] / ([V FIELD RATE RQD] / [V FIELD RATE EST])
419 h_period = DIVIDE(h_period_est * v_field_est, v_field_rqd * 1000);
421 print_value(12, "[H PERIOD(ps)]", h_period);
424 /* 13. Find the actual Vertical field frequency:
426 * [V FIELD RATE] = 1 / [H PERIOD] / [TOTAL V LINES] * 1000000
428 * And again, we convert to nsec ahead of time, giving us:
430 * [V FIELD RATE] = 1000000 / [H PERIOD] / [TOTAL V LINES]
432 * And another rescaling back to mHz. Gotta love it.
435 v_field_rate = DIVIDE(1000000000000ULL, h_period * total_v_lines);
437 print_value(13, "[V FIELD RATE]", v_field_rate);
440 /* 14. Find the Vertical frame frequency:
442 * [V FRAME RATE] = (IF([INT RQD?]="y", [V FIELD RATE]/2, [V FIELD RATE]))
444 * N.B. that the result here is in mHz.
447 v_frame_rate = (flags & VESAGTF_FLAG_ILACE) ?
448 v_field_rate / 2 : v_field_rate;
450 print_value(14, "[V FRAME RATE]", v_frame_rate);
453 /* 15. Find number of pixels in left margin:
454 * 16. Find number of pixels in right margin:
456 * [LEFT MARGIN (PIXELS)] = (IF( [MARGINS RQD?]="Y",
457 * (ROUND( ([H PIXELS RND] * [MARGIN%] / 100 /
458 * [CELL GRAN RND]),0)) * [CELL GRAN RND],
461 * Again, we deal with margin percentages as PPT (parts per thousand).
462 * And the calculations for left and right are the same.
465 left_margin = right_margin = (flags & VESAGTF_FLAG_MARGINS) ?
466 DIVIDE(DIVIDE(h_pixels * params->margin_ppt, 1000),
467 CELL_GRAN) * CELL_GRAN : 0;
469 print_value(15, "[LEFT MARGIN (PIXELS)]", left_margin);
470 print_value(16, "[RIGHT MARGIN (PIXELS)]", right_margin);
473 /* 17. Find total number of active pixels in image and left and right
476 * [TOTAL ACTIVE PIXELS] = [H PIXELS RND] + [LEFT MARGIN (PIXELS)] +
477 * [RIGHT MARGIN (PIXELS)]
480 total_active_pixels = h_pixels + left_margin + right_margin;
482 print_value(17, "[TOTAL ACTIVE PIXELS]", total_active_pixels);
485 /* 18. Find the ideal blanking duty cycle from the blanking duty cycle
488 * [IDEAL DUTY CYCLE] = [C'] - ([M']*[H PERIOD]/1000)
490 * However, we have modified values for [C'] as [256*C'] and
491 * [M'] as [256*M']. Again the idea here is to get good scaling.
492 * We use 256 as the factor to make the math fast.
494 * Note that this means that we have to scale it appropriately in
495 * later calculations.
497 * The ending result is that our ideal_duty_cycle is 256000x larger
498 * than the duty cycle used by VESA. But again, this reduces error
503 ((C_PRIME256(params) * 1000) -
504 (M_PRIME256(params) * h_period / 1000000));
506 print_value(18, "[IDEAL DUTY CYCLE]", ideal_duty_cycle);
509 /* 19. Find the number of pixels in the blanking time to the nearest
510 * double character cell:
512 * [H BLANK (PIXELS)] = (ROUND(([TOTAL ACTIVE PIXELS] *
513 * [IDEAL DUTY CYCLE] /
514 * (100-[IDEAL DUTY CYCLE]) /
515 * (2*[CELL GRAN RND])), 0))
516 * * (2*[CELL GRAN RND])
518 * Of course, we adjust to make this rounding work in integer math.
521 h_blank = DIVIDE(DIVIDE(total_active_pixels * ideal_duty_cycle,
522 (256000 * 100ULL) - ideal_duty_cycle),
523 2 * CELL_GRAN) * (2 * CELL_GRAN);
525 print_value(19, "[H BLANK (PIXELS)]", h_blank);
528 /* 20. Find total number of pixels:
530 * [TOTAL PIXELS] = [TOTAL ACTIVE PIXELS] + [H BLANK (PIXELS)]
533 total_pixels = total_active_pixels + h_blank;
535 print_value(20, "[TOTAL PIXELS]", total_pixels);
538 /* 21. Find pixel clock frequency:
540 * [PIXEL FREQ] = [TOTAL PIXELS] / [H PERIOD]
542 * We calculate this in Hz rather than MHz, to get a value that
543 * is usable with integer math. Recall that the [H PERIOD] is in
547 pixel_freq = DIVIDE(total_pixels * 1000000, DIVIDE(h_period, 1000));
549 print_value(21, "[PIXEL FREQ]", pixel_freq);
552 /* 22. Find horizontal frequency:
554 * [H FREQ] = 1000 / [H PERIOD]
556 * I've ifdef'd this out, because we don't need it for any of
558 * We calculate this in Hz rather than kHz, to avoid rounding
559 * errors. Recall that the [H PERIOD] is in usec.
563 h_freq = 1000000000 / h_period;
565 print_value(22, "[H FREQ]", h_freq);
570 /* Stage 1 computations are now complete; I should really pass
571 the results to another function and do the Stage 2
572 computations, but I only need a few more values so I'll just
573 append the computations here for now */
577 /* 17. Find the number of pixels in the horizontal sync period:
579 * [H SYNC (PIXELS)] =(ROUND(([H SYNC%] / 100 * [TOTAL PIXELS] /
580 * [CELL GRAN RND]),0))*[CELL GRAN RND]
582 * Rewriting for integer math:
584 * [H SYNC (PIXELS)]=(ROUND((H SYNC%] * [TOTAL PIXELS] / 100 /
585 * [CELL GRAN RND),0))*[CELL GRAN RND]
588 h_sync = DIVIDE(((params->hsync_pct * total_pixels) / 100), CELL_GRAN) *
591 print_value(17, "[H SYNC (PIXELS)]", h_sync);
594 /* 18. Find the number of pixels in the horizontal front porch period:
596 * [H FRONT PORCH (PIXELS)] = ([H BLANK (PIXELS)]/2)-[H SYNC (PIXELS)]
598 * Note that h_blank is always an even number of characters (i.e.
599 * h_blank % (CELL_GRAN * 2) == 0)
602 h_front_porch = (h_blank / 2) - h_sync;
604 print_value(18, "[H FRONT PORCH (PIXELS)]", h_front_porch);
607 /* 36. Find the number of lines in the odd front porch period:
609 * [V ODD FRONT PORCH(LINES)]=([MIN PORCH RND]+[INTERLACE])
611 * Adjusting for the fact that the interlace is scaled:
613 * [V ODD FRONT PORCH(LINES)]=(([MIN PORCH RND] * 2) + [2*INTERLACE]) / 2
616 v_odd_front_porch_lines = ((2 * params->min_porch) + interlace) / 2;
618 print_value(36, "[V ODD FRONT PORCH(LINES)]", v_odd_front_porch_lines);
621 /* finally, pack the results in the mode struct */
623 vmp->hsync_start = h_pixels + h_front_porch;
624 vmp->hsync_end = vmp->hsync_start + h_sync;
625 vmp->htotal = total_pixels;
626 vmp->hdisplay = h_pixels;
628 vmp->vsync_start = v_lines + v_odd_front_porch_lines;
629 vmp->vsync_end = vmp->vsync_start + params->vsync_rqd;
630 vmp->vtotal = total_v_lines;
631 vmp->vdisplay = v_lines;
633 vmp->dot_clock = pixel_freq;
638 vesagtf_mode(unsigned x, unsigned y, unsigned refresh, struct videomode *vmp)
640 struct vesagtf_params params;
642 params.margin_ppt = VESAGTF_MARGIN_PPT;
643 params.min_porch = VESAGTF_MIN_PORCH;
644 params.vsync_rqd = VESAGTF_VSYNC_RQD;
645 params.hsync_pct = VESAGTF_HSYNC_PCT;
646 params.min_vsbp = VESAGTF_MIN_VSBP;
647 params.M = VESAGTF_M;
648 params.C = VESAGTF_C;
649 params.K = VESAGTF_K;
650 params.J = VESAGTF_J;
652 vesagtf_mode_params(x, y, refresh, ¶ms, 0, vmp);
656 * The tidbit here is so that you can compile this file as a
657 * standalone user program to generate X11 modelines using VESA GTF.
658 * This also allows for testing of the code itself, without
659 * necessitating a full kernel recompile.
662 /* print_xf86_mode() - print the XFree86 modeline, given mode timings. */
666 print_xf86_mode (struct videomode *vmp)
670 hf = 1000.0 * vmp->dot_clock / vmp->htotal;
671 vf = 1.0 * hf / vmp->vtotal;
674 printf(" # %dx%d @ %.2f Hz (GTF) hsync: %.2f kHz; pclk: %.2f MHz\n",
675 vmp->hdisplay, vmp->vdisplay, vf, hf, vmp->dot_clock / 1000.0);
677 printf(" Modeline \"%dx%d_%.2f\" %.2f"
680 " -HSync +Vsync\n\n",
681 vmp->hdisplay, vmp->vdisplay, vf, (vmp->dot_clock / 1000.0),
682 vmp->hdisplay, vmp->hsync_start, vmp->hsync_end, vmp->htotal,
683 vmp->vdisplay, vmp->vsync_start, vmp->vsync_end, vmp->vtotal);
687 main (int argc, char *argv[])
692 printf("usage: %s x y refresh\n", argv[0]);
696 vesagtf_mode(atoi(argv[1]), atoi(argv[2]), atoi(argv[3]), &m);