drm/mode: add the GTF algorithm in kernel space

Add the GTF algorithm in kernel space. And this function can be called to
generate the required modeline.

I copied it from the file of xserver/hw/xfree86/modes/xf86gtf.c. What I have
done is to translate it by using integer calculation. This is to avoid
the float-point calculation in kernel space.
At the same tie I also refer to the function of fb_get_mode in
drivers/video/fbmon.c
Signed-off-by: Zhao Yakui <yakui.zhao@intel.com>
Signed-off-by: Dave Airlie <airlied@linux.ie>

drivers/gpu/drm/drm_modes.c

@@ -9,6 +9,7 @@
  * Copyright © 2007-2008 Intel Corporation
  *   Jesse Barnes <jesse.barnes@intel.com>
  * Copyright 2005-2006 Luc Verhaegen
+ * Copyright (c) 2001, Andy Ritger  aritger@nvidia.com
  *
  * Permission is hereby granted, free of charge, to any person obtaining a
  * copy of this software and associated documentation files (the "Software"),
@@ -280,6 +281,202 @@ struct drm_display_mode *drm_cvt_mode(struct drm_device *dev, int hdisplay,
 }
 EXPORT_SYMBOL(drm_cvt_mode);
 
+/**
+ * drm_gtf_mode - create the modeline based on GTF algorithm
+ *
+ * @dev		:drm device
+ * @hdisplay	:hdisplay size
+ * @vdisplay	:vdisplay size
+ * @vrefresh	:vrefresh rate.
+ * @interlaced	:whether the interlace is supported
+ * @margins	:whether the margin is supported
+ *
+ * LOCKING.
+ * none.
+ *
+ * return the modeline based on GTF algorithm
+ *
+ * This function is to create the modeline based on the GTF algorithm.
+ * Generalized Timing Formula is derived from:
+ *	GTF Spreadsheet by Andy Morrish (1/5/97)
+ *	available at http://www.vesa.org
+ *
+ * And it is copied from the file of xserver/hw/xfree86/modes/xf86gtf.c.
+ * What I have done is to translate it by using integer calculation.
+ * I also refer to the function of fb_get_mode in the file of
+ * drivers/video/fbmon.c
+ */
+struct drm_display_mode *drm_gtf_mode(struct drm_device *dev, int hdisplay,
+				      int vdisplay, int vrefresh,
+				      bool interlaced, int margins)
+{
+	/* 1) top/bottom margin size (% of height) - default: 1.8, */
+#define	GTF_MARGIN_PERCENTAGE		18
+	/* 2) character cell horizontal granularity (pixels) - default 8 */
+#define	GTF_CELL_GRAN			8
+	/* 3) Minimum vertical porch (lines) - default 3 */
+#define	GTF_MIN_V_PORCH			1
+	/* width of vsync in lines */
+#define V_SYNC_RQD			3
+	/* width of hsync as % of total line */
+#define H_SYNC_PERCENT			8
+	/* min time of vsync + back porch (microsec) */
+#define MIN_VSYNC_PLUS_BP		550
+	/* blanking formula gradient */
+#define GTF_M				600
+	/* blanking formula offset */
+#define GTF_C				40
+	/* blanking formula scaling factor */
+#define GTF_K				128
+	/* blanking formula scaling factor */
+#define GTF_J				20
+	/* C' and M' are part of the Blanking Duty Cycle computation */
+#define GTF_C_PRIME		(((GTF_C - GTF_J) * GTF_K / 256) + GTF_J)
+#define GTF_M_PRIME		(GTF_K * GTF_M / 256)
+	struct drm_display_mode *drm_mode;
+	unsigned int hdisplay_rnd, vdisplay_rnd, vfieldrate_rqd;
+	int top_margin, bottom_margin;
+	int interlace;
+	unsigned int hfreq_est;
+	int vsync_plus_bp, vback_porch;
+	unsigned int vtotal_lines, vfieldrate_est, hperiod;
+	unsigned int vfield_rate, vframe_rate;
+	int left_margin, right_margin;
+	unsigned int total_active_pixels, ideal_duty_cycle;
+	unsigned int hblank, total_pixels, pixel_freq;
+	int hsync, hfront_porch, vodd_front_porch_lines;
+	unsigned int tmp1, tmp2;
+
+	drm_mode = drm_mode_create(dev);
+	if (!drm_mode)
+		return NULL;
+
+	/* 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:
+	 */
+	hdisplay_rnd = (hdisplay + GTF_CELL_GRAN / 2) / GTF_CELL_GRAN;
+	hdisplay_rnd = hdisplay_rnd * GTF_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.
+	 */
+	if (interlaced)
+		vdisplay_rnd = vdisplay / 2;
+	else
+		vdisplay_rnd = vdisplay;
+
+	/* 3. Find the frame rate required: */
+	if (interlaced)
+		vfieldrate_rqd = vrefresh * 2;
+	else
+		vfieldrate_rqd = vrefresh;
+
+	/* 4. Find number of lines in Top margin: */
+	top_margin = 0;
+	if (margins)
+		top_margin = (vdisplay_rnd * GTF_MARGIN_PERCENTAGE + 500) /
+				1000;
+	/* 5. Find number of lines in bottom margin: */
+	bottom_margin = top_margin;
+
+	/* 6. If interlace is required, then set variable interlace: */
+	if (interlaced)
+		interlace = 1;
+	else
+		interlace = 0;
+
+	/* 7. Estimate the Horizontal frequency */
+	{
+		tmp1 = (1000000  - MIN_VSYNC_PLUS_BP * vfieldrate_rqd) / 500;
+		tmp2 = (vdisplay_rnd + 2 * top_margin + GTF_MIN_V_PORCH) *
+				2 + interlace;
+		hfreq_est = (tmp2 * 1000 * vfieldrate_rqd) / tmp1;
+	}
+
+	/* 8. Find the number of lines in V sync + back porch */
+	/* [V SYNC+BP] = RINT(([MIN VSYNC+BP] * hfreq_est / 1000000)) */
+	vsync_plus_bp = MIN_VSYNC_PLUS_BP * hfreq_est / 1000;
+	vsync_plus_bp = (vsync_plus_bp + 500) / 1000;
+	/*  9. Find the number of lines in V back porch alone: */
+	vback_porch = vsync_plus_bp - V_SYNC_RQD;
+	/*  10. Find the total number of lines in Vertical field period: */
+	vtotal_lines = vdisplay_rnd + top_margin + bottom_margin +
+			vsync_plus_bp + GTF_MIN_V_PORCH;
+	/*  11. Estimate the Vertical field frequency: */
+	vfieldrate_est = hfreq_est / vtotal_lines;
+	/*  12. Find the actual horizontal period: */
+	hperiod = 1000000 / (vfieldrate_rqd * vtotal_lines);
+
+	/*  13. Find the actual Vertical field frequency: */
+	vfield_rate = hfreq_est / vtotal_lines;
+	/*  14. Find the Vertical frame frequency: */
+	if (interlaced)
+		vframe_rate = vfield_rate / 2;
+	else
+		vframe_rate = vfield_rate;
+	/*  15. Find number of pixels in left margin: */
+	if (margins)
+		left_margin = (hdisplay_rnd * GTF_MARGIN_PERCENTAGE + 500) /
+				1000;
+	else
+		left_margin = 0;
+
+	/* 16.Find number of pixels in right margin: */
+	right_margin = left_margin;
+	/* 17.Find total number of active pixels in image and left and right */
+	total_active_pixels = hdisplay_rnd + left_margin + right_margin;
+	/* 18.Find the ideal blanking duty cycle from blanking duty cycle */
+	ideal_duty_cycle = GTF_C_PRIME * 1000 -
+				(GTF_M_PRIME * 1000000 / hfreq_est);
+	/* 19.Find the number of pixels in the blanking time to the nearest
+	 * double character cell: */
+	hblank = total_active_pixels * ideal_duty_cycle /
+			(100000 - ideal_duty_cycle);
+	hblank = (hblank + GTF_CELL_GRAN) / (2 * GTF_CELL_GRAN);
+	hblank = hblank * 2 * GTF_CELL_GRAN;
+	/* 20.Find total number of pixels: */
+	total_pixels = total_active_pixels + hblank;
+	/* 21.Find pixel clock frequency: */
+	pixel_freq = total_pixels * hfreq_est / 1000;
+	/* 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: */
+	hsync = H_SYNC_PERCENT * total_pixels / 100;
+	hsync = (hsync + GTF_CELL_GRAN / 2) / GTF_CELL_GRAN;
+	hsync = hsync * GTF_CELL_GRAN;
+	/* 18. Find the number of pixels in horizontal front porch period */
+	hfront_porch = hblank / 2 - hsync;
+	/*  36. Find the number of lines in the odd front porch period: */
+	vodd_front_porch_lines = GTF_MIN_V_PORCH ;
+
+	/* finally, pack the results in the mode struct */
+	drm_mode->hdisplay = hdisplay_rnd;
+	drm_mode->hsync_start = hdisplay_rnd + hfront_porch;
+	drm_mode->hsync_end = drm_mode->hsync_start + hsync;
+	drm_mode->htotal = total_pixels;
+	drm_mode->vdisplay = vdisplay_rnd;
+	drm_mode->vsync_start = vdisplay_rnd + vodd_front_porch_lines;
+	drm_mode->vsync_end = drm_mode->vsync_start + V_SYNC_RQD;
+	drm_mode->vtotal = vtotal_lines;
+
+	drm_mode->clock = pixel_freq;
+
+	drm_mode_set_name(drm_mode);
+	drm_mode->flags = DRM_MODE_FLAG_NHSYNC | DRM_MODE_FLAG_PVSYNC;
+
+	if (interlaced) {
+		drm_mode->vtotal *= 2;
+		drm_mode->flags |= DRM_MODE_FLAG_INTERLACE;
+	}
+
+	return drm_mode;
+}
+EXPORT_SYMBOL(drm_gtf_mode);
 /**
  * drm_mode_set_name - set the name on a mode
  * @mode: name will be set in this mode

include/drm/drm_crtc.h

@@ -739,4 +739,7 @@ extern bool drm_detect_hdmi_monitor(struct edid *edid);
 extern struct drm_display_mode *drm_cvt_mode(struct drm_device *dev,
 				int hdisplay, int vdisplay, int vrefresh,
 				bool reduced, bool interlaced);
+extern struct drm_display_mode *drm_gtf_mode(struct drm_device *dev,
+				int hdisplay, int vdisplay, int vrefresh,
+				bool interlaced, int margins);
 #endif /* __DRM_CRTC_H__ */