/**************************************************************************** * video/videomode/vesagtf.c * * SPDX-License-Identifier: Apache-2.0 * * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. The * ASF licenses this file to you under the Apache License, Version 2.0 (the * "License"); you may not use this file except in compliance with the * License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the * License for the specific language governing permissions and limitations * under the License. * ****************************************************************************/ /* 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 #include #include /**************************************************************************** * 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); }