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linux/drivers/video/fbdev/core/fbcvt.c
Tomi Valkeinen 4d073292a7 fbdev: fix CVT vertical front and back porch values 
CVT v1.1 spec says: "the vertical front porch shall in all cases be
fixed to 3 lines". The code in fbcvt.c instead sets the _back_ porch to
3 (plus margin).

After swapping cvt.v_front_porch and cvt.v_back_porch the resulting
timings were in line with CVT timings in VESA DMT spec.

The bug seems to be more than 9 years old, but I presume it has not been
noticed as usually the video timings come from the EDID or from the
timing tables in fbdev, and probably swapped values for vfp and vbp work
fine for most of the displays.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Acked-by: David Ung <davidu@nvidia.com>
Cc: Antonino A. Daplas <adaplas@gmail.com>
2015-01-27 13:35:37 +02:00

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/*
* linux/drivers/video/fbcvt.c - VESA(TM) Coordinated Video Timings
*
* Copyright (C) 2005 Antonino Daplas <adaplas@pol.net>
*
* Based from the VESA(TM) Coordinated Video Timing Generator by
* Graham Loveridge April 9, 2003 available at
* http://www.elo.utfsm.cl/~elo212/docs/CVTd6r1.xls
*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file COPYING in the main directory of this archive
* for more details.
*
*/
#include <linux/fb.h>
#include <linux/slab.h>
#define FB_CVT_CELLSIZE 8
#define FB_CVT_GTF_C 40
#define FB_CVT_GTF_J 20
#define FB_CVT_GTF_K 128
#define FB_CVT_GTF_M 600
#define FB_CVT_MIN_VSYNC_BP 550
#define FB_CVT_MIN_VPORCH 3
#define FB_CVT_MIN_BPORCH 6
#define FB_CVT_RB_MIN_VBLANK 460
#define FB_CVT_RB_HBLANK 160
#define FB_CVT_RB_V_FPORCH 3
#define FB_CVT_FLAG_REDUCED_BLANK 1
#define FB_CVT_FLAG_MARGINS 2
#define FB_CVT_FLAG_INTERLACED 4
struct fb_cvt_data {
u32 xres;
u32 yres;
u32 refresh;
u32 f_refresh;
u32 pixclock;
u32 hperiod;
u32 hblank;
u32 hfreq;
u32 htotal;
u32 vtotal;
u32 vsync;
u32 hsync;
u32 h_front_porch;
u32 h_back_porch;
u32 v_front_porch;
u32 v_back_porch;
u32 h_margin;
u32 v_margin;
u32 interlace;
u32 aspect_ratio;
u32 active_pixels;
u32 flags;
u32 status;
};
static const unsigned char fb_cvt_vbi_tab[] = {
4, /* 4:3 */
5, /* 16:9 */
6, /* 16:10 */
7, /* 5:4 */
7, /* 15:9 */
8, /* reserved */
9, /* reserved */
10 /* custom */
};
/* returns hperiod * 1000 */
static u32 fb_cvt_hperiod(struct fb_cvt_data *cvt)
{
u32 num = 1000000000/cvt->f_refresh;
u32 den;
if (cvt->flags & FB_CVT_FLAG_REDUCED_BLANK) {
num -= FB_CVT_RB_MIN_VBLANK * 1000;
den = 2 * (cvt->yres/cvt->interlace + 2 * cvt->v_margin);
} else {
num -= FB_CVT_MIN_VSYNC_BP * 1000;
den = 2 * (cvt->yres/cvt->interlace + cvt->v_margin * 2
+ FB_CVT_MIN_VPORCH + cvt->interlace/2);
}
return 2 * (num/den);
}
/* returns ideal duty cycle * 1000 */
static u32 fb_cvt_ideal_duty_cycle(struct fb_cvt_data *cvt)
{
u32 c_prime = (FB_CVT_GTF_C - FB_CVT_GTF_J) *
(FB_CVT_GTF_K) + 256 * FB_CVT_GTF_J;
u32 m_prime = (FB_CVT_GTF_K * FB_CVT_GTF_M);
u32 h_period_est = cvt->hperiod;
return (1000 * c_prime - ((m_prime * h_period_est)/1000))/256;
}
static u32 fb_cvt_hblank(struct fb_cvt_data *cvt)
{
u32 hblank = 0;
if (cvt->flags & FB_CVT_FLAG_REDUCED_BLANK)
hblank = FB_CVT_RB_HBLANK;
else {
u32 ideal_duty_cycle = fb_cvt_ideal_duty_cycle(cvt);
u32 active_pixels = cvt->active_pixels;
if (ideal_duty_cycle < 20000)
hblank = (active_pixels * 20000)/
(100000 - 20000);
else {
hblank = (active_pixels * ideal_duty_cycle)/
(100000 - ideal_duty_cycle);
}
}
hblank &= ~((2 * FB_CVT_CELLSIZE) - 1);
return hblank;
}
static u32 fb_cvt_hsync(struct fb_cvt_data *cvt)
{
u32 hsync;
if (cvt->flags & FB_CVT_FLAG_REDUCED_BLANK)
hsync = 32;
else
hsync = (FB_CVT_CELLSIZE * cvt->htotal)/100;
hsync &= ~(FB_CVT_CELLSIZE - 1);
return hsync;
}
static u32 fb_cvt_vbi_lines(struct fb_cvt_data *cvt)
{
u32 vbi_lines, min_vbi_lines, act_vbi_lines;
if (cvt->flags & FB_CVT_FLAG_REDUCED_BLANK) {
vbi_lines = (1000 * FB_CVT_RB_MIN_VBLANK)/cvt->hperiod + 1;
min_vbi_lines = FB_CVT_RB_V_FPORCH + cvt->vsync +
FB_CVT_MIN_BPORCH;
} else {
vbi_lines = (FB_CVT_MIN_VSYNC_BP * 1000)/cvt->hperiod + 1 +
FB_CVT_MIN_VPORCH;
min_vbi_lines = cvt->vsync + FB_CVT_MIN_BPORCH +
FB_CVT_MIN_VPORCH;
}
if (vbi_lines < min_vbi_lines)
act_vbi_lines = min_vbi_lines;
else
act_vbi_lines = vbi_lines;
return act_vbi_lines;
}
static u32 fb_cvt_vtotal(struct fb_cvt_data *cvt)
{
u32 vtotal = cvt->yres/cvt->interlace;
vtotal += 2 * cvt->v_margin + cvt->interlace/2 + fb_cvt_vbi_lines(cvt);
vtotal |= cvt->interlace/2;
return vtotal;
}
static u32 fb_cvt_pixclock(struct fb_cvt_data *cvt)
{
u32 pixclock;
if (cvt->flags & FB_CVT_FLAG_REDUCED_BLANK)
pixclock = (cvt->f_refresh * cvt->vtotal * cvt->htotal)/1000;
else
pixclock = (cvt->htotal * 1000000)/cvt->hperiod;
pixclock /= 250;
pixclock *= 250;
pixclock *= 1000;
return pixclock;
}
static u32 fb_cvt_aspect_ratio(struct fb_cvt_data *cvt)
{
u32 xres = cvt->xres;
u32 yres = cvt->yres;
u32 aspect = -1;
if (xres == (yres * 4)/3 && !((yres * 4) % 3))
aspect = 0;
else if (xres == (yres * 16)/9 && !((yres * 16) % 9))
aspect = 1;
else if (xres == (yres * 16)/10 && !((yres * 16) % 10))
aspect = 2;
else if (xres == (yres * 5)/4 && !((yres * 5) % 4))
aspect = 3;
else if (xres == (yres * 15)/9 && !((yres * 15) % 9))
aspect = 4;
else {
printk(KERN_INFO "fbcvt: Aspect ratio not CVT "
"standard\n");
aspect = 7;
cvt->status = 1;
}
return aspect;
}
static void fb_cvt_print_name(struct fb_cvt_data *cvt)
{
u32 pixcount, pixcount_mod;
int cnt = 255, offset = 0, read = 0;
u8 *buf = kzalloc(256, GFP_KERNEL);
if (!buf)
return;
pixcount = (cvt->xres * (cvt->yres/cvt->interlace))/1000000;
pixcount_mod = (cvt->xres * (cvt->yres/cvt->interlace)) % 1000000;
pixcount_mod /= 1000;
read = snprintf(buf+offset, cnt, "fbcvt: %dx%d@%d: CVT Name - ",
cvt->xres, cvt->yres, cvt->refresh);
offset += read;
cnt -= read;
if (cvt->status)
snprintf(buf+offset, cnt, "Not a CVT standard - %d.%03d Mega "
"Pixel Image\n", pixcount, pixcount_mod);
else {
if (pixcount) {
read = snprintf(buf+offset, cnt, "%d", pixcount);
cnt -= read;
offset += read;
}
read = snprintf(buf+offset, cnt, ".%03dM", pixcount_mod);
cnt -= read;
offset += read;
if (cvt->aspect_ratio == 0)
read = snprintf(buf+offset, cnt, "3");
else if (cvt->aspect_ratio == 3)
read = snprintf(buf+offset, cnt, "4");
else if (cvt->aspect_ratio == 1 || cvt->aspect_ratio == 4)
read = snprintf(buf+offset, cnt, "9");
else if (cvt->aspect_ratio == 2)
read = snprintf(buf+offset, cnt, "A");
else
read = 0;
cnt -= read;
offset += read;
if (cvt->flags & FB_CVT_FLAG_REDUCED_BLANK) {
read = snprintf(buf+offset, cnt, "-R");
cnt -= read;
offset += read;
}
}
printk(KERN_INFO "%s\n", buf);
kfree(buf);
}
static void fb_cvt_convert_to_mode(struct fb_cvt_data *cvt,
struct fb_videomode *mode)
{
mode->refresh = cvt->f_refresh;
mode->pixclock = KHZ2PICOS(cvt->pixclock/1000);
mode->left_margin = cvt->h_back_porch;
mode->right_margin = cvt->h_front_porch;
mode->hsync_len = cvt->hsync;
mode->upper_margin = cvt->v_back_porch;
mode->lower_margin = cvt->v_front_porch;
mode->vsync_len = cvt->vsync;
mode->sync &= ~(FB_SYNC_HOR_HIGH_ACT | FB_SYNC_VERT_HIGH_ACT);
if (cvt->flags & FB_CVT_FLAG_REDUCED_BLANK)
mode->sync |= FB_SYNC_HOR_HIGH_ACT;
else
mode->sync |= FB_SYNC_VERT_HIGH_ACT;
}
/*
* fb_find_mode_cvt - calculate mode using VESA(TM) CVT
* @mode: pointer to fb_videomode; xres, yres, refresh and vmode must be
* pre-filled with the desired values
* @margins: add margin to calculation (1.8% of xres and yres)
* @rb: compute with reduced blanking (for flatpanels)
*
* RETURNS:
* 0 for success
* @mode is filled with computed values. If interlaced, the refresh field
* will be filled with the field rate (2x the frame rate)
*
* DESCRIPTION:
* Computes video timings using VESA(TM) Coordinated Video Timings
*/
int fb_find_mode_cvt(struct fb_videomode *mode, int margins, int rb)
{
struct fb_cvt_data cvt;
memset(&cvt, 0, sizeof(cvt));
if (margins)
cvt.flags |= FB_CVT_FLAG_MARGINS;
if (rb)
cvt.flags |= FB_CVT_FLAG_REDUCED_BLANK;
if (mode->vmode & FB_VMODE_INTERLACED)
cvt.flags |= FB_CVT_FLAG_INTERLACED;
cvt.xres = mode->xres;
cvt.yres = mode->yres;
cvt.refresh = mode->refresh;
cvt.f_refresh = cvt.refresh;
cvt.interlace = 1;
if (!cvt.xres || !cvt.yres || !cvt.refresh) {
printk(KERN_INFO "fbcvt: Invalid input parameters\n");
return 1;
}
if (!(cvt.refresh == 50 || cvt.refresh == 60 || cvt.refresh == 70 ||
cvt.refresh == 85)) {
printk(KERN_INFO "fbcvt: Refresh rate not CVT "
"standard\n");
cvt.status = 1;
}
cvt.xres &= ~(FB_CVT_CELLSIZE - 1);
if (cvt.flags & FB_CVT_FLAG_INTERLACED) {
cvt.interlace = 2;
cvt.f_refresh *= 2;
}
if (cvt.flags & FB_CVT_FLAG_REDUCED_BLANK) {
if (cvt.refresh != 60) {
printk(KERN_INFO "fbcvt: 60Hz refresh rate "
"advised for reduced blanking\n");
cvt.status = 1;
}
}
if (cvt.flags & FB_CVT_FLAG_MARGINS) {
cvt.h_margin = (cvt.xres * 18)/1000;
cvt.h_margin &= ~(FB_CVT_CELLSIZE - 1);
cvt.v_margin = ((cvt.yres/cvt.interlace)* 18)/1000;
}
cvt.aspect_ratio = fb_cvt_aspect_ratio(&cvt);
cvt.active_pixels = cvt.xres + 2 * cvt.h_margin;
cvt.hperiod = fb_cvt_hperiod(&cvt);
cvt.vsync = fb_cvt_vbi_tab[cvt.aspect_ratio];
cvt.vtotal = fb_cvt_vtotal(&cvt);
cvt.hblank = fb_cvt_hblank(&cvt);
cvt.htotal = cvt.active_pixels + cvt.hblank;
cvt.hsync = fb_cvt_hsync(&cvt);
cvt.pixclock = fb_cvt_pixclock(&cvt);
cvt.hfreq = cvt.pixclock/cvt.htotal;
cvt.h_back_porch = cvt.hblank/2 + cvt.h_margin;
cvt.h_front_porch = cvt.hblank - cvt.hsync - cvt.h_back_porch +
2 * cvt.h_margin;
cvt.v_front_porch = 3 + cvt.v_margin;
cvt.v_back_porch = cvt.vtotal - cvt.yres/cvt.interlace -
cvt.v_front_porch - cvt.vsync;
fb_cvt_print_name(&cvt);
fb_cvt_convert_to_mode(&cvt, mode);
return 0;
}
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