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- /****************************************************************************
- * video/videomode/vesagtf.c
- *
- * Copyright (C) 2019 Gregory Nutt. All rights reserved.
- * Author: Gregory Nutt <gnutt@nuttx.org>
- *
- * Derives from logic in FreeBSD which has an equivalent 3-clause BSD
- * license:
- *
- * Copyright (c) 2006 Itronix Inc. All rights reserved.
- * Written by Garrett D'Amore for Itronix Inc.
- *
- * That version, in turn, derived from a userland GTF program supplied by
- * Nvidia which was also released under a compatible 3-clause BSD license:
- *
- * Copyright (c) 2001, Andy Ritger <aritger@nvidia.com>
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- *
- * 1. Redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- * notice, this list of conditions and the following disclaimer in the
- * documentation and/or other materials provided with the distribution.
- * 3. The name of Itronix Inc. may not be used to endorse
- * or promote products derived from this software without specific
- * prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY ITRONIX INC. ``AS IS'' AND ANY EXPRESS
- * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
- * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
- * ARE DISCLAIMED. IN NO EVENT SHALL ITRONIX INC. BE LIABLE FOR ANY
- * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
- * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
- * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
- * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
- * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
- * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- *
- ****************************************************************************/
- /* The logic in this file program was based on the Generalized Timing
- * Formula(GTF TM) Standard Version: 1.0, Revision: 1.0
- *
- * NOTES:
- *
- * The GTF allows for computation of "margins" (the visible border
- * surrounding the addressable video); on most non-overscan type
- * systems, the margin period is zero. I've implemented the margin
- * computations but not enabled it because 1) I don't really have
- * any experience with this, and 2) neither XFree86 modelines nor
- * fbset fb.modes provide an obvious way for margin timings to be
- * included in their mode descriptions (needs more investigation).
- *
- * The GTF provides for computation of interlaced mode timings;
- * I've implemented the computations but not enabled them, yet.
- * I should probably enable and test this at some point.
- *
- * TODO:
- *
- * o Add support for interlaced modes.
- *
- * o Implement the other portions of the GTF: compute mode timings
- * given either the desired pixel clock or the desired horizontal
- * frequency.
- *
- * o It would be nice if this were more general purpose to do things
- * outside the scope of the GTF: like generate double scan mode
- * timings, for example.
- *
- * o Printing digits to the right of the decimal point when the
- * digits are 0 annoys me.
- *
- * o Error checking.
- */
- /****************************************************************************
- * Included Files
- ****************************************************************************/
- #include <sys/types.h>
- #include <nuttx/video/videomode.h>
- #include <nuttx/video/vesagtf.h>
- /****************************************************************************
- * Pre-processor Definitions
- ****************************************************************************/
- #define CELL_GRAN 8 /* Assumed character cell granularity */
- /* c' and m' are part of the Blanking Duty Cycle computation
- *
- * #define C_PRIME (((c - j) * k/256.0) + j)
- * #define M_PRIME (k/256.0 * m)
- */
- /* c' and m' multiplied by 256 to give integer math. Make sure to
- * scale results using these back down, appropriately.
- */
- #define C_PRIME256(p) (((p->c - p->j) * p->k) + (p->j * 256))
- #define M_PRIME256(p) (p->k * p->m)
- #define DIVIDE(x,y) (((x) + ((y) / 2)) / (y))
- /****************************************************************************
- * Public Functions
- ****************************************************************************/
- /****************************************************************************
- * Name: vesagtf_mode_params
- *
- * Description:
- * vesagtf_mode_params() - as defined by the GTF Timing Standard, compute
- * the Stage 1 Parameters using the vertical refresh frequency. In other
- * words: input a desired resolution and desired refresh rate, and
- * output the GTF mode timings.
- *
- ****************************************************************************/
- void vesagtf_mode_params(unsigned int x, unsigned int y,
- unsigned int refresh,
- FAR struct vesagtf_params *params,
- unsigned int flags,
- FAR struct videomode_s *videomode)
- {
- uint64_t h_period_est;
- uint64_t v_field_est;
- uint64_t h_period;
- uint64_t ideal_duty_cycle;
- unsigned int v_field_rqd;
- unsigned int top_margin;
- unsigned int bottom_margin;
- unsigned int interlace;
- unsigned int vsync_plus_bp;
- unsigned total_v_lines;
- unsigned int left_margin;
- unsigned int right_margin;
- unsigned int total_active_pixels;
- unsigned int h_blank;
- unsigned int h_pixels;
- unsigned int v_lines;
- unsigned int total_pixels;
- unsigned int pixel_freq;
- unsigned int h_sync;
- unsigned int h_front_porch;
- unsigned int v_odd_front_porch_lines;
- #if 0 /* Unused, not needed */
- unsigned int v_field_rate;
- unsigned int v_back_porch;
- unsigned int v_frame_rate;
- unsigned int h_freq;
- #endif
- /* 1. In order to give correct results, the number of horizontal
- * pixels requested is first processed to ensure that it is divisible
- * by the character size, by rounding it to the nearest character
- * cell boundary:
- *
- * [H PIXELS RND] = ((ROUND([H PIXELS]/[CELL GRAN RND],0))*[CELLGRAN RND])
- */
- h_pixels = DIVIDE(x, CELL_GRAN) * CELL_GRAN;
- /* 2. If interlace is requested, the number of vertical lines assumed
- * by the calculation must be halved, as the computation calculates
- * the number of vertical lines per field. In either case, the
- * number of lines is rounded to the nearest integer.
- *
- * [V LINES RND] = IF([INT RQD?]="y", ROUND([V LINES]/2,0),
- * ROUND([V LINES],0))
- */
- v_lines = (flags & VESAGTF_FLAG_ILACE) ? DIVIDE(y, 2) : y;
- /* 3. Find the frame rate required:
- *
- * [V FIELD RATE RQD] = IF([INT RQD?]="y", [I/P FREQ RQD]*2,
- * [I/P FREQ RQD])
- */
- v_field_rqd = (flags & VESAGTF_FLAG_ILACE) ? (refresh * 2) : (refresh);
- /* 4. Find number of lines in Top margin:
- * 5. Find number of lines in Bottom margin:
- *
- * [TOP MARGIN (LINES)] = IF([MARGINS RQD?]="Y",
- * ROUND(([MARGIN%]/100*[V LINES RND]),0),
- * 0)
- *
- * Ditto for bottom margin. Note that instead of %, we use PPT, which
- * is parts per thousand. This helps us with integer math.
- */
- top_margin = (flags & VESAGTF_FLAG_MARGINS) ?
- DIVIDE(v_lines * params->margin_ppt, 1000) : 0;
- bottom_margin = top_margin;
- /* 6. If interlace is required, then set variable [INTERLACE]=0.5:
- *
- * [INTERLACE]=(IF([INT RQD?]="y",0.5,0))
- *
- * To make this integer friendly, we use some special hacks in step
- * 7 below. Please read those comments to understand why I am using
- * a whole number of 1.0 instead of 0.5 here.
- */
- interlace = (flags & VESAGTF_FLAG_ILACE) ? 1 : 0;
- /* 7. Estimate the Horizontal period
- *
- * [H PERIOD EST] = ((1/[V FIELD RATE RQD]) - [MIN VSYNC+BP]/1000000) /
- * ([V LINES RND] + (2*[TOP MARGIN (LINES)]) +
- * [MIN PORCH RND]+[INTERLACE]) * 1000000
- *
- * To make it integer friendly, we pre-multiply the 1000000 to get to
- * usec. This gives us:
- *
- * [H PERIOD EST] = ((1000000/[V FIELD RATE RQD]) - [MIN VSYNC+BP]) /
- * ([V LINES RND] + (2 * [TOP MARGIN (LINES)]) +
- * [MIN PORCH RND]+[INTERLACE])
- *
- * The other problem is that the interlace value is wrong. To get
- * the interlace to a whole number, we multiply both the numerator and
- * divisor by 2, so we can use a value of either 1 or 0 for the interlace
- * factor.
- *
- * This gives us:
- *
- * [H PERIOD EST] = ((2*((1000000/[V FIELD RATE RQD]) - [MIN VSYNC+BP])) /
- * (2*([V LINES RND] + (2*[TOP MARGIN (LINES)]) +
- * [MIN PORCH RND]) + [2*INTERLACE]))
- *
- * Finally we multiply by another 1000, to get value in picosec.
- * Why picosec? To minimize rounding errors. Gotta love integer
- * math and error propagation.
- */
- h_period_est = DIVIDE(((DIVIDE(2000000000000ULL, v_field_rqd)) -
- (2000000 * params->min_vsbp)),
- ((2 * (v_lines +
- (2 * top_margin) + params->min_porch)) +
- interlace));
- /* 8. Find the number of lines in V sync + back porch:
- *
- * [V SYNC+BP] = ROUND(([MIN VSYNC+BP]/[H PERIOD EST]),0)
- *
- * But recall that h_period_est is in psec. So multiply by 1000000.
- */
- vsync_plus_bp = DIVIDE(params->min_vsbp * 1000000, h_period_est);
- #if 0 /* Not needed */
- /* 9. Find the number of lines in V back porch alone:
- *
- * [V BACK PORCH] = [V SYNC+BP] - [V SYNC RND]
- *
- * XXX is "[V SYNC RND]" a typo? should be [V SYNC RQD]?
- */
- v_back_porch = vsync_plus_bp - params->vsync_rqd;
- #endif
- /* 10. Find the total number of lines in Vertical field period:
- *
- * [TOTAL V LINES] = [V LINES RND] + [TOP MARGIN (LINES)] +
- * [BOT MARGIN (LINES)] + [V SYNC+BP] + [INTERLACE] +
- * [MIN PORCH RND]
- */
- total_v_lines = v_lines + top_margin + bottom_margin + vsync_plus_bp +
- interlace + params->min_porch;
- /* 11. Estimate the Vertical field frequency:
- *
- * [V FIELD RATE EST] = 1 / [H PERIOD EST] / [TOTAL V LINES] * 1000000
- *
- * Again, we want to pre multiply by 10^9 to convert for nsec, thereby
- * making it usable in integer math.
- *
- * So we get:
- *
- * [V FIELD RATE EST] = 1000000000 / [H PERIOD EST] / [TOTAL V LINES]
- *
- * This is all scaled to get the result in uHz. Again, we're trying to
- * minimize error propagation.
- */
- v_field_est = DIVIDE(DIVIDE(1000000000000000ULL, h_period_est),
- total_v_lines);
- /* 12. Find the actual horizontal period:
- *
- * [H PERIOD] = [H PERIOD EST] / ([V FIELD RATE RQD] / [V FIELD RATE EST])
- */
- h_period = DIVIDE(h_period_est * v_field_est, v_field_rqd * 1000);
- #if 0 /* Not needed */
- /* 13. Find the actual Vertical field frequency:
- *
- * [V FIELD RATE] = 1 / [H PERIOD] / [TOTAL V LINES] * 1000000
- *
- * And again, we convert to nsec ahead of time, giving us:
- *
- * [V FIELD RATE] = 1000000 / [H PERIOD] / [TOTAL V LINES]
- *
- * And another rescaling back to mHz. Gotta love it.
- */
- v_field_rate = DIVIDE(1000000000000ULL, h_period * total_v_lines);
- /* 14. Find the Vertical frame frequency:
- *
- * [V FRAME RATE] = (IF([INT RQD?]="y", [V FIELD RATE]/2, [V FIELD RATE]))
- *
- * N.B. that the result here is in mHz.
- */
- v_frame_rate = (flags & VESAGTF_FLAG_ILACE) ?
- v_field_rate / 2 : v_field_rate;
- #endif
- /* 15. Find number of pixels in left margin:
- * 16. Find number of pixels in right margin:
- *
- * [LEFT MARGIN (PIXELS)] = (IF( [MARGINS RQD?]="Y",
- * (ROUND( ([H PIXELS RND] * [MARGIN%] / 100 /
- * [CELL GRAN RND]),0)) * [CELL GRAN RND],
- * 0))
- *
- * Again, we deal with margin percentages as PPT (parts per thousand).
- * And the calculations for left and right are the same.
- */
- left_margin = right_margin = (flags & VESAGTF_FLAG_MARGINS) ?
- DIVIDE(DIVIDE(h_pixels * params->margin_ppt, 1000),
- CELL_GRAN) * CELL_GRAN : 0;
- /* 17. Find total number of active pixels in image and left and right
- * margins:
- *
- * [TOTAL ACTIVE PIXELS] = [H PIXELS RND] + [LEFT MARGIN (PIXELS)] +
- * [RIGHT MARGIN (PIXELS)]
- */
- total_active_pixels = h_pixels + left_margin + right_margin;
- /* 18. Find the ideal blanking duty cycle from the blanking duty cycle
- * equation:
- *
- * [IDEAL DUTY CYCLE] = [c'] - ([m']*[H PERIOD]/1000)
- *
- * However, we have modified values for [c'] as [256*c'] and
- * [m'] as [256*m']. Again the idea here is to get good scaling.
- * We use 256 as the factor to make the math fast.
- *
- * Note that this means that we have to scale it appropriately in
- * later calculations.
- *
- * The ending result is that our ideal_duty_cycle is 256000x larger
- * than the duty cycle used by VESA. But again, this reduces error
- * propagation.
- */
- ideal_duty_cycle =
- ((C_PRIME256(params) * 1000) -
- (M_PRIME256(params) * h_period / 1000000));
- /* 19. Find the number of pixels in the blanking time to the nearest
- * double character cell:
- *
- * [H BLANK (PIXELS)] = (ROUND(([TOTAL ACTIVE PIXELS] *
- * [IDEAL DUTY CYCLE] /
- * (100-[IDEAL DUTY CYCLE]) /
- * (2*[CELL GRAN RND])), 0))
- * * (2*[CELL GRAN RND])
- *
- * Of course, we adjust to make this rounding work in integer math.
- */
- h_blank = DIVIDE(DIVIDE(total_active_pixels * ideal_duty_cycle,
- (256000 * 100ULL) - ideal_duty_cycle),
- 2 * CELL_GRAN) * (2 * CELL_GRAN);
- /* 20. Find total number of pixels:
- *
- * [TOTAL PIXELS] = [TOTAL ACTIVE PIXELS] + [H BLANK (PIXELS)]
- */
- total_pixels = total_active_pixels + h_blank;
- /* 21. Find pixel clock frequency:
- *
- * [PIXEL FREQ] = [TOTAL PIXELS] / [H PERIOD]
- *
- * We calculate this in Hz rather than MHz, to get a value that
- * is usable with integer math. Recall that the [H PERIOD] is in
- * nsec.
- */
- pixel_freq = DIVIDE(total_pixels * 1000000, DIVIDE(h_period, 1000));
- #if 0 /* Not needed */
- /* 22. Find horizontal frequency:
- *
- * [H FREQ] = 1000 / [H PERIOD]
- *
- * We calculate this in Hz rather than kHz, to avoid rounding
- * errors. Recall that the [H PERIOD] is in usec.
- */
- h_freq = 1000000000 / h_period;
- #endif
- /* Stage 1 computations are now complete; I should really pass
- * the results to another function and do the Stage 2
- * computations, but I only need a few more values so I'll just
- * append the computations here for now.
- */
- /* 17. Find the number of pixels in the horizontal sync period:
- *
- * [H SYNC (PIXELS)] =(ROUND(([H SYNC%] / 100 * [TOTAL PIXELS] /
- * [CELL GRAN RND]),0))*[CELL GRAN RND]
- *
- * Rewriting for integer math:
- *
- * [H SYNC (PIXELS)]=(ROUND((H SYNC%] * [TOTAL PIXELS] / 100 /
- * [CELL GRAN RND),0))*[CELL GRAN RND]
- */
- h_sync = DIVIDE(((params->hsync_pct * total_pixels) / 100), CELL_GRAN) *
- CELL_GRAN;
- /* 18. Find the number of pixels in the horizontal front porch period:
- *
- * [H FRONT PORCH (PIXELS)] = ([H BLANK (PIXELS)]/2)-[H SYNC (PIXELS)]
- *
- * Note that h_blank is always an even number of characters (i.e.
- * h_blank % (CELL_GRAN * 2) == 0)
- */
- h_front_porch = (h_blank / 2) - h_sync;
- /* 36. Find the number of lines in the odd front porch period:
- *
- * [V ODD FRONT PORCH(LINES)]=([MIN PORCH RND]+[INTERLACE])
- *
- * Adjusting for the fact that the interlace is scaled:
- *
- * [V ODD FRONT PORCH(LINES)]=(([MIN PORCH RND] * 2) + [2*INTERLACE]) / 2
- */
- v_odd_front_porch_lines = ((2 * params->min_porch) + interlace) / 2;
- /* finally, pack the results in the mode struct */
- videomode->hsync_start = h_pixels + h_front_porch;
- videomode->hsync_end = videomode->hsync_start + h_sync;
- videomode->htotal = total_pixels;
- videomode->hdisplay = h_pixels;
- videomode->vsync_start = v_lines + v_odd_front_porch_lines;
- videomode->vsync_end = videomode->vsync_start + params->vsync_rqd;
- videomode->vtotal = total_v_lines;
- videomode->vdisplay = v_lines;
- videomode->dotclock = pixel_freq;
- }
- /****************************************************************************
- * Name: vesagtf_mode
- *
- * Description:
- * Use VESA GTF formula to generate monitor timings. Assumes default
- * GTF parameters, non-interlaced, and no margins.
- *
- ****************************************************************************/
- void vesagtf_mode(unsigned int x, unsigned int y, unsigned int refresh,
- FAR struct videomode_s *videomode)
- {
- struct vesagtf_params params;
- params.margin_ppt = VESAGTF_MARGIN_PPT;
- params.min_porch = VESAGTF_MIN_PORCH;
- params.vsync_rqd = VESAGTF_VSYNC_RQD;
- params.hsync_pct = VESAGTF_HSYNC_PCT;
- params.min_vsbp = VESAGTF_MIN_VSBP;
- params.m = VESAGTF_M;
- params.c = VESAGTF_C;
- params.k = VESAGTF_K;
- params.j = VESAGTF_J;
- vesagtf_mode_params(x, y, refresh, ¶ms, 0, videomode);
- }
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