drm/mode: add the CVT algorithm in kernel space

Add the CVT 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/xf86cvt.c. What I have
done is to translate it by using integer calculation. This is to avoid
the float-point calculation in kernel space.

[airlied:- cleaned up some bits]
Signed-off-by: Zhao Yakui <yakui.zhao@intel.com>
Signed-off-by: Dave Airlie <airlied@linux.ie>

drivers/gpu/drm/drm_modes.c

@@ -8,6 +8,7 @@
  * Copyright © 2007 Dave Airlie
  * Copyright © 2007-2008 Intel Corporation
  *   Jesse Barnes <jesse.barnes@intel.com>
+ * 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"),
@@ -61,6 +62,224 @@ void drm_mode_debug_printmodeline(struct drm_display_mode *mode)
 }
 EXPORT_SYMBOL(drm_mode_debug_printmodeline);
 
+/**
+ * drm_cvt_mode -create a modeline based on CVT algorithm
+ * @dev: DRM device
+ * @hdisplay: hdisplay size
+ * @vdisplay: vdisplay size
+ * @vrefresh  : vrefresh rate
+ * @reduced : Whether the GTF calculation is simplified
+ * @interlaced:Whether the interlace is supported
+ *
+ * LOCKING:
+ * none.
+ *
+ * return the modeline based on CVT algorithm
+ *
+ * This function is called to generate the modeline based on CVT algorithm
+ * according to the hdisplay, vdisplay, vrefresh.
+ * It is based from the VESA(TM) Coordinated Video Timing Generator by
+ * Graham Loveridge April 9, 2003 available at
+ * http://www.vesa.org/public/CVT/CVTd6r1.xls
+ *
+ * And it is copied from xf86CVTmode in xserver/hw/xfree86/modes/xf86cvt.c.
+ * What I have done is to translate it by using integer calculation.
+ */
+#define HV_FACTOR			1000
+struct drm_display_mode *drm_cvt_mode(struct drm_device *dev, int hdisplay,
+				      int vdisplay, int vrefresh,
+				      bool reduced, bool interlaced)
+{
+	/* 1) top/bottom margin size (% of height) - default: 1.8, */
+#define	CVT_MARGIN_PERCENTAGE		18
+	/* 2) character cell horizontal granularity (pixels) - default 8 */
+#define	CVT_H_GRANULARITY		8
+	/* 3) Minimum vertical porch (lines) - default 3 */
+#define	CVT_MIN_V_PORCH			3
+	/* 4) Minimum number of vertical back porch lines - default 6 */
+#define	CVT_MIN_V_BPORCH		6
+	/* Pixel Clock step (kHz) */
+#define CVT_CLOCK_STEP			250
+	struct drm_display_mode *drm_mode;
+	bool margins = false;
+	unsigned int vfieldrate, hperiod;
+	int hdisplay_rnd, hmargin, vdisplay_rnd, vmargin, vsync;
+	int interlace;
+
+	/* allocate the drm_display_mode structure. If failure, we will
+	 * return directly
+	 */
+	drm_mode = drm_mode_create(dev);
+	if (!drm_mode)
+		return NULL;
+
+	/* the CVT default refresh rate is 60Hz */
+	if (!vrefresh)
+		vrefresh = 60;
+
+	/* the required field fresh rate */
+	if (interlaced)
+		vfieldrate = vrefresh * 2;
+	else
+		vfieldrate = vrefresh;
+
+	/* horizontal pixels */
+	hdisplay_rnd = hdisplay - (hdisplay % CVT_H_GRANULARITY);
+
+	/* determine the left&right borders */
+	hmargin = 0;
+	if (margins) {
+		hmargin = hdisplay_rnd * CVT_MARGIN_PERCENTAGE / 1000;
+		hmargin -= hmargin % CVT_H_GRANULARITY;
+	}
+	/* find the total active pixels */
+	drm_mode->hdisplay = hdisplay_rnd + 2 * hmargin;
+
+	/* find the number of lines per field */
+	if (interlaced)
+		vdisplay_rnd = vdisplay / 2;
+	else
+		vdisplay_rnd = vdisplay;
+
+	/* find the top & bottom borders */
+	vmargin = 0;
+	if (margins)
+		vmargin = vdisplay_rnd * CVT_MARGIN_PERCENTAGE / 1000;
+
+	drm_mode->vdisplay = vdisplay_rnd + 2 * vmargin;
+
+	/* Interlaced */
+	if (interlaced)
+		interlace = 1;
+	else
+		interlace = 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) {
+		/* simplify the GTF calculation */
+		/* 4) Minimum time of vertical sync + back porch interval (µs)
+		 * default 550.0
+		 */
+		int tmp1, tmp2;
+#define CVT_MIN_VSYNC_BP	550
+		/* 3) Nominal HSync width (% of line period) - default 8 */
+#define CVT_HSYNC_PERCENTAGE	8
+		unsigned int hblank_percentage;
+		int vsyncandback_porch, vback_porch, hblank;
+
+		/* estimated the horizontal period */
+		tmp1 = HV_FACTOR * 1000000  -
+				CVT_MIN_VSYNC_BP * HV_FACTOR * vfieldrate;
+		tmp2 = (vdisplay_rnd + 2 * vmargin + CVT_MIN_V_PORCH) * 2 +
+				interlace;
+		hperiod = tmp1 * 2 / (tmp2 * vfieldrate);
+
+		tmp1 = CVT_MIN_VSYNC_BP * HV_FACTOR / hperiod + 1;
+		/* 9. Find number of lines in sync + backporch */
+		if (tmp1 < (vsync + CVT_MIN_V_PORCH))
+			vsyncandback_porch = vsync + CVT_MIN_V_PORCH;
+		else
+			vsyncandback_porch = tmp1;
+		/* 10. Find number of lines in back porch */
+		vback_porch = vsyncandback_porch - vsync;
+		drm_mode->vtotal = vdisplay_rnd + 2 * vmargin +
+				vsyncandback_porch + CVT_MIN_V_PORCH;
+		/* 5) 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)
+		/* 12. Find ideal blanking duty cycle from formula */
+		hblank_percentage = CVT_C_PRIME * HV_FACTOR - CVT_M_PRIME *
+					hperiod / 1000;
+		/* 13. Blanking time */
+		if (hblank_percentage < 20 * HV_FACTOR)
+			hblank_percentage = 20 * HV_FACTOR;
+		hblank = drm_mode->hdisplay * hblank_percentage /
+			 (100 * HV_FACTOR - hblank_percentage);
+		hblank -= hblank % (2 * CVT_H_GRANULARITY);
+		/* 14. find the total pixes per line */
+		drm_mode->htotal = drm_mode->hdisplay + hblank;
+		drm_mode->hsync_end = drm_mode->hdisplay + hblank / 2;
+		drm_mode->hsync_start = drm_mode->hsync_end -
+			(drm_mode->htotal * CVT_HSYNC_PERCENTAGE) / 100;
+		drm_mode->hsync_start += CVT_H_GRANULARITY -
+			drm_mode->hsync_start % CVT_H_GRANULARITY;
+		/* fill the Vsync values */
+		drm_mode->vsync_start = drm_mode->vdisplay + CVT_MIN_V_PORCH;
+		drm_mode->vsync_end = drm_mode->vsync_start + vsync;
+	} else {
+		/* Reduced blanking */
+		/* Minimum vertical blanking interval time (µs)- default 460 */
+#define CVT_RB_MIN_VBLANK	460
+		/* Fixed number of clocks for horizontal sync */
+#define CVT_RB_H_SYNC		32
+		/* Fixed number of clocks for horizontal blanking */
+#define CVT_RB_H_BLANK		160
+		/* Fixed number of lines for vertical front porch - default 3*/
+#define CVT_RB_VFPORCH		3
+		int vbilines;
+		int tmp1, tmp2;
+		/* 8. Estimate Horizontal period. */
+		tmp1 = HV_FACTOR * 1000000 -
+			CVT_RB_MIN_VBLANK * HV_FACTOR * vfieldrate;
+		tmp2 = vdisplay_rnd + 2 * vmargin;
+		hperiod = tmp1 / (tmp2 * vfieldrate);
+		/* 9. Find number of lines in vertical blanking */
+		vbilines = CVT_RB_MIN_VBLANK * HV_FACTOR / hperiod + 1;
+		/* 10. Check if vertical blanking is sufficient */
+		if (vbilines < (CVT_RB_VFPORCH + vsync + CVT_MIN_V_BPORCH))
+			vbilines = CVT_RB_VFPORCH + vsync + CVT_MIN_V_BPORCH;
+		/* 11. Find total number of lines in vertical field */
+		drm_mode->vtotal = vdisplay_rnd + 2 * vmargin + vbilines;
+		/* 12. Find total number of pixels in a line */
+		drm_mode->htotal = drm_mode->hdisplay + CVT_RB_H_BLANK;
+		/* Fill in HSync values */
+		drm_mode->hsync_end = drm_mode->hdisplay + CVT_RB_H_BLANK / 2;
+		drm_mode->hsync_start = drm_mode->hsync_end = CVT_RB_H_SYNC;
+	}
+	/* 15/13. Find pixel clock frequency (kHz for xf86) */
+	drm_mode->clock = drm_mode->htotal * HV_FACTOR * 1000 / hperiod;
+	drm_mode->clock -= drm_mode->clock % CVT_CLOCK_STEP;
+	/* 18/16. Find actual vertical frame frequency */
+	/* ignore - just set the mode flag for interlaced */
+	if (interlaced)
+		drm_mode->vtotal *= 2;
+	/* Fill the mode line name */
+	drm_mode_set_name(drm_mode);
+	if (reduced)
+		drm_mode->flags |= (DRM_MODE_FLAG_PHSYNC |
+					DRM_MODE_FLAG_NVSYNC);
+	else
+		drm_mode->flags |= (DRM_MODE_FLAG_PVSYNC |
+					DRM_MODE_FLAG_NHSYNC);
+	if (interlaced)
+		drm_mode->flags |= DRM_MODE_FLAG_INTERLACE;
+
+    return drm_mode;
+}
+EXPORT_SYMBOL(drm_cvt_mode);
+
 /**
  * drm_mode_set_name - set the name on a mode
  * @mode: name will be set in this mode

include/drm/drm_crtc.h

@@ -736,4 +736,7 @@ extern int drm_mode_gamma_get_ioctl(struct drm_device *dev,
 extern int drm_mode_gamma_set_ioctl(struct drm_device *dev,
 				    void *data, struct drm_file *file_priv);
 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);
 #endif /* __DRM_CRTC_H__ */