drm/mode: add the GTF algorithm in kernel space

 * 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"),

}

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

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__ */