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wlroots/backend/drm/cvt.c

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/*
* Copyright 2005-2006 Luc Verhaegen.
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
* OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
* OTHER DEALINGS IN THE SOFTWARE.
*/
#include "backend/drm/cvt.h"
/* top/bottom margin size (% of height) - default: 1.8 */
#define CVT_MARGIN_PERCENTAGE 1.8
/* character cell horizontal granularity (pixels) - default 8 */
#define CVT_H_GRANULARITY 8
/* Minimum vertical porch (lines) - default 3 */
#define CVT_MIN_V_PORCH 3
/* Minimum number of vertical back porch lines - default 6 */
#define CVT_MIN_V_BPORCH 6
/* Pixel clock step (kHz) */
#define CVT_CLOCK_STEP 250
/* Minimum time of vertical sync + back porch interval (µs)
* default 550.0 */
#define CVT_MIN_VSYNC_BP 550.0
/* Nominal hsync width (% of line period) - default 8 */
#define CVT_HSYNC_PERCENTAGE 8
/* Definition of Horizontal blanking time limitation */
/* Gradient (%/kHz) - default 600 */
#define CVT_M_FACTOR 600
/* Offset (%) - default 40 */
#define CVT_C_FACTOR 40
/* Blanking time scaling factor - default 128 */
#define CVT_K_FACTOR 128
/* Scaling factor weighting - default 20 */
#define CVT_J_FACTOR 20
#define CVT_M_PRIME CVT_M_FACTOR * CVT_K_FACTOR / 256
#define CVT_C_PRIME (CVT_C_FACTOR - CVT_J_FACTOR) * CVT_K_FACTOR / 256 + \
CVT_J_FACTOR
/* Minimum vertical blanking interval time (µs) - default 460 */
#define CVT_RB_MIN_VBLANK 460.0
/* Fixed number of clocks for horizontal sync */
#define CVT_RB_H_SYNC 32.0
/* Fixed number of clocks for horizontal blanking */
#define CVT_RB_H_BLANK 160.0
/* Fixed number of lines for vertical front porch - default 3 */
#define CVT_RB_VFPORCH 3
/*
* Generate a CVT standard mode from hdisplay, vdisplay and vrefresh.
*
* These calculations are stolen from the CVT calculation spreadsheet written
* by Graham Loveridge. He seems to be claiming no copyright and there seems to
* be no license attached to this. He apparently just wants to see his name
* mentioned.
*
* This file can be found at http://www.vesa.org/Public/CVT/CVTd6r1.xls
*
* Comments and structure corresponds to the comments and structure of the xls.
* This should ease importing of future changes to the standard (not very
* likely though).
*
* This function is borrowed from xorg-xserver's xf86CVTmode.
*/
void generate_cvt_mode(drmModeModeInfo *mode, int hdisplay, int vdisplay,
float vrefresh, bool reduced, bool interlaced) {
bool margins = false;
float vfield_rate, hperiod;
int hdisplay_rnd, hmargin;
int vdisplay_rnd, vmargin, vsync;
float interlace; /* Please rename this */
/* CVT default is 60.0Hz */
if (!vrefresh) {
vrefresh = 60.0;
}
/* 1. Required field rate */
if (interlaced) {
vfield_rate = vrefresh * 2;
} else {
vfield_rate = vrefresh;
}
/* 2. Horizontal pixels */
hdisplay_rnd = hdisplay - (hdisplay % CVT_H_GRANULARITY);
/* 3. Determine left and right borders */
if (margins) {
/* right margin is actually exactly the same as left */
hmargin = (((float) hdisplay_rnd) * CVT_MARGIN_PERCENTAGE / 100.0);
hmargin -= hmargin % CVT_H_GRANULARITY;
} else {
hmargin = 0;
}
/* 4. Find total active pixels */
mode->hdisplay = hdisplay_rnd + 2 * hmargin;
/* 5. Find number of lines per field */
if (interlaced) {
vdisplay_rnd = vdisplay / 2;
} else {
vdisplay_rnd = vdisplay;
}
/* 6. Find top and bottom margins */
/* nope. */
if (margins) {
/* top and bottom margins are equal again. */
vmargin = (((float) vdisplay_rnd) * CVT_MARGIN_PERCENTAGE / 100.0);
} else {
vmargin = 0;
}
mode->vdisplay = vdisplay + 2 * vmargin;
/* 7. interlace */
if (interlaced) {
interlace = 0.5;
} else {
interlace = 0.0;
}
/* Determine vsync Width from aspect ratio */
if (!(vdisplay % 3) && ((vdisplay * 4 / 3) == hdisplay)) {
vsync = 4;
} else if (!(vdisplay % 9) && ((vdisplay * 16 / 9) == hdisplay)) {
vsync = 5;
} else if (!(vdisplay % 10) && ((vdisplay * 16 / 10) == hdisplay)) {
vsync = 6;
} else if (!(vdisplay % 4) && ((vdisplay * 5 / 4) == hdisplay)) {
vsync = 7;
} else if (!(vdisplay % 9) && ((vdisplay * 15 / 9) == hdisplay)) {
vsync = 7;
} else { /* Custom */
vsync = 10;
}
if (!reduced) { /* simplified GTF calculation */
float hblank_percentage;
int vsync_and_back_porch, vblank_porch;
int hblank;
/* 8. Estimated Horizontal period */
hperiod = ((float) (1000000.0 / vfield_rate - CVT_MIN_VSYNC_BP)) /
(vdisplay_rnd + 2 * vmargin + CVT_MIN_V_PORCH + interlace);
/* 9. Find number of lines in sync + backporch */
if (((int) (CVT_MIN_VSYNC_BP / hperiod) + 1) <
(vsync + CVT_MIN_V_PORCH)) {
vsync_and_back_porch = vsync + CVT_MIN_V_PORCH;
} else {
vsync_and_back_porch = (int) (CVT_MIN_VSYNC_BP / hperiod) + 1;
}
/* 10. Find number of lines in back porch */
vblank_porch = vsync_and_back_porch - vsync;
(void) vblank_porch;
/* 11. Find total number of lines in vertical field */
mode->vtotal = vdisplay_rnd + 2 * vmargin + vsync_and_back_porch + interlace
+ CVT_MIN_V_PORCH;
/* 12. Find ideal blanking duty cycle from formula */
hblank_percentage = CVT_C_PRIME - CVT_M_PRIME * hperiod / 1000.0;
/* 13. Blanking time */
if (hblank_percentage < 20) {
hblank_percentage = 20;
}
hblank = mode->hdisplay * hblank_percentage / (100.0 - hblank_percentage);
hblank -= hblank % (2 * CVT_H_GRANULARITY);
/* 14. Find total number of pixels in a line. */
mode->htotal = mode->hdisplay + hblank;
/* Fill in hsync values */
mode->hsync_end = mode->hdisplay + hblank / 2;
mode->hsync_start = mode->hsync_end -
(mode->htotal * CVT_HSYNC_PERCENTAGE) / 100;
mode->hsync_start += CVT_H_GRANULARITY -
mode->hsync_start % CVT_H_GRANULARITY;
/* Fill in vsync values */
mode->vsync_start = mode->vdisplay + CVT_MIN_V_PORCH;
mode->vsync_end = mode->vsync_start + vsync;
} else { /* reduced blanking */
int vbi_lines;
/* 8. Estimate Horizontal period. */
hperiod = ((float) (1000000.0 / vfield_rate - CVT_RB_MIN_VBLANK)) /
(vdisplay_rnd + 2 * vmargin);
/* 9. Find number of lines in vertical blanking */
vbi_lines = ((float) CVT_RB_MIN_VBLANK) / hperiod + 1;
/* 10. Check if vertical blanking is sufficient */
if (vbi_lines < (CVT_RB_VFPORCH + vsync + CVT_MIN_V_BPORCH)) {
vbi_lines = CVT_RB_VFPORCH + vsync + CVT_MIN_V_BPORCH;
}
/* 11. Find total number of lines in vertical field */
mode->vtotal = vdisplay_rnd + 2 * vmargin + interlace + vbi_lines;
/* 12. Find total number of pixels in a line */
mode->htotal = mode->hdisplay + CVT_RB_H_BLANK;
/* Fill in hsync values */
mode->hsync_end = mode->hdisplay + CVT_RB_H_BLANK / 2;
mode->hsync_start = mode->hsync_end - CVT_RB_H_SYNC;
/* Fill in vsync values */
mode->vsync_start = mode->vdisplay + CVT_RB_VFPORCH;
mode->vsync_end = mode->vsync_start + vsync;
}
/* 15/13. Find pixel clock frequency (kHz for xf86) */
mode->clock = mode->htotal * 1000.0 / hperiod;
mode->clock -= mode->clock % CVT_CLOCK_STEP;
/* 17/15. Find actual Field rate */
mode->vrefresh = (1000.0 * ((float) mode->clock)) /
((float) (mode->htotal * mode->vtotal));
/* 18/16. Find actual vertical frame frequency */
/* ignore - just set the mode flag for interlaced */
if (interlaced) {
mode->vtotal *= 2;
mode->flags |= DRM_MODE_FLAG_INTERLACE;
}
snprintf(mode->name, sizeof(mode->name), "%dx%d", hdisplay, vdisplay);
if (reduced) {
mode->flags |= DRM_MODE_FLAG_PHSYNC | DRM_MODE_FLAG_NVSYNC;
} else {
mode->flags |= DRM_MODE_FLAG_NHSYNC | DRM_MODE_FLAG_PVSYNC;
}
}
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