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drm/mode: add the GTF algorithm in kernel space
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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>
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Zhao Yakui authored and Dave Airlie committed Jul 15, 2009
1 parent d782c3f commit 26bbdad
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197 changes: 197 additions & 0 deletions drivers/gpu/drm/drm_modes.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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"),
Expand Down Expand Up @@ -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
Expand Down
3 changes: 3 additions & 0 deletions include/drm/drm_crtc.h
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Original file line number Diff line number Diff line change
Expand Up @@ -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__ */

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