backend/drm: add support for custom modes

Use the CVT algorithm to create a drmModeModeInfo.

5 files changed, 307 insertions, 6 deletions

diff --git a/backend/drm/cvt.c b/backend/drm/cvt.c
new file mode 100644
index 00000000..40f156b7
--- /dev/null
+++ b/backend/drm/cvt.c
@@ -0,0 +1,269 @@
+/*
+ * 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;
+	}
+}
diff --git a/backend/drm/drm.c b/backend/drm/drm.c
index de9ddc09..9bcafeb6 100644
--- a/backend/drm/drm.c
+++ b/backend/drm/drm.c
@@ -23,6 +23,7 @@
 #include <wlr/util/log.h>
 #include <xf86drm.h>
 #include <xf86drmMode.h>
+#include "backend/drm/cvt.h"
 #include "backend/drm/drm.h"
 #include "backend/drm/iface.h"
 #include "backend/drm/util.h"
@@ -672,25 +673,39 @@ bool drm_connector_set_mode(struct wlr_output *output,
 	return true;
 }
 
-bool wlr_drm_connector_add_mode(struct wlr_output *output,
+static bool drm_connector_set_custom_mode(struct wlr_output *output,
+		int32_t width, int32_t height, int32_t refresh) {
+	drmModeModeInfo mode = {0};
+	generate_cvt_mode(&mode, width, height, (float)refresh / 1000, false, false);
+	mode.type = DRM_MODE_TYPE_USERDEF;
+
+	struct wlr_output_mode *wlr_mode = wlr_drm_connector_add_mode(output, &mode);
+	if (wlr_mode == NULL) {
+		return false;
+	}
+
+	return drm_connector_set_mode(output, wlr_mode);
+}
+
+struct wlr_output_mode *wlr_drm_connector_add_mode(struct wlr_output *output,
 		const drmModeModeInfo *modeinfo) {
 	struct wlr_drm_connector *conn = get_drm_connector_from_output(output);
 
 	if (modeinfo->type != DRM_MODE_TYPE_USERDEF) {
-		return false;
+		return NULL;
 	}
 
 	struct wlr_output_mode *wlr_mode;
 	wl_list_for_each(wlr_mode, &conn->output.modes, link) {
 		struct wlr_drm_mode *mode = (struct wlr_drm_mode *)wlr_mode;
 		if (memcmp(&mode->drm_mode, modeinfo, sizeof(*modeinfo)) == 0) {
-			return true;
+			return wlr_mode;
 		}
 	}
 
 	struct wlr_drm_mode *mode = calloc(1, sizeof(*mode));
 	if (!mode) {
-		return false;
+		return NULL;
 	}
 	memcpy(&mode->drm_mode, modeinfo, sizeof(*modeinfo));
 
@@ -703,7 +718,8 @@ bool wlr_drm_connector_add_mode(struct wlr_output *output,
 			mode->wlr_mode.width, mode->wlr_mode.height,
 			mode->wlr_mode.refresh);
 	wl_list_insert(&conn->output.modes, &mode->wlr_mode.link);
-	return true;
+
+	return &mode->wlr_mode;
 }
 
 static bool drm_connector_set_cursor(struct wlr_output *output,
@@ -988,6 +1004,7 @@ static void drm_connector_destroy(struct wlr_output *output) {
 static const struct wlr_output_impl output_impl = {
 	.enable = enable_drm_connector,
 	.set_mode = drm_connector_set_mode,
+	.set_custom_mode = drm_connector_set_custom_mode,
 	.set_cursor = drm_connector_set_cursor,
 	.move_cursor = drm_connector_move_cursor,
 	.destroy = drm_connector_destroy,
diff --git a/backend/meson.build b/backend/meson.build
index 574d4f74..e4a484f4 100644
--- a/backend/meson.build
+++ b/backend/meson.build
@@ -3,6 +3,7 @@ backend_files = files(
 	'backend.c',
 	'drm/atomic.c',
 	'drm/backend.c',
+	'drm/cvt.c',
 	'drm/drm.c',
 	'drm/legacy.c',
 	'drm/properties.c',
diff --git a/include/backend/drm/cvt.h b/include/backend/drm/cvt.h
new file mode 100644
index 00000000..34db5384
--- /dev/null
+++ b/include/backend/drm/cvt.h
@@ -0,0 +1,13 @@
+#ifndef BACKEND_DRM_CVT_H
+#define BACKEND_DRM_CVT_H
+
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <xf86drmMode.h>
+
+void generate_cvt_mode(drmModeModeInfo *mode, int hdisplay, int vdisplay,
+	float vrefresh, bool reduced, bool interlaced);
+
+#endif
diff --git a/include/wlr/backend/drm.h b/include/wlr/backend/drm.h
index e4b5e2d1..c1380323 100644
--- a/include/wlr/backend/drm.h
+++ b/include/wlr/backend/drm.h
@@ -32,6 +32,7 @@ bool wlr_output_is_drm(struct wlr_output *output);
  * Add mode to the list of available modes
  */
 typedef struct _drmModeModeInfo drmModeModeInfo;
-bool wlr_drm_connector_add_mode(struct wlr_output *output, const drmModeModeInfo *mode);
+struct wlr_output_mode *wlr_drm_connector_add_mode(struct wlr_output *output,
+	const drmModeModeInfo *mode);
 
 #endif