[Xorg-driver-geode] display mode with 800x480 on geode-2.11.1

[John Yoder]

I apologize for not getting back to you sooner. To answer your earlier
question about adding a resolution that is currently not available, I
would submit a patch, as I believe I can infer that you are using the
VGA port rather then a direct connect to the panel connector. It
simplifies things a bit.

As I recall, the table entries are as follows:
  <name>  <refresh,> <xres> <yres> <pixclock> <left_margin>
<right_margin> <upper_margin> <lower_margin> < hsync_length>
<vsync_length> <sync> <vmode>
What is required are derived by calculation from modelines. So you will
need to get a working custom modeline to start. Then some calculations.
Lets start with an explanation of the fields:

    pixclock - pixel clock in pico seconds (I believe this is correct)
    left_margin - time from sync to picture
    right_margin - time from picture to sync
    upper_margin - time from sync to picture
    lower_margin - time from picture to sync
    hsync_lenth - length of horizontal sync
    vsync_length - length of vertical sync

Modelines have the following fields

    Modeline <name> <DCL> <HR> <HPS> <HPE> <HFL> <VR> <VPS> <VPE> <VFL>

Where:
    name - name assigned to mode
    DCL - Dot Clock (MHz)
    HR & VR - Horizontal and Vertical resolution
    HPS, HPE, VPS, VPE - Horizontal and Vertical Pulse Start and End
also known as Front and Back Porch
    HFL & VFL - Horizontal and Vertical Field Length

To get values that are required for these the calculations are as
follows:
    left_margin = HFL - HPE
    right_margin = HPS - HR
    hsync_length = HFE - HPS

    upper_margin = VFL - VPE
    lower_margin = VPS - VR
    vsync_length = VPE - VPS

This should get you close. This information was pulled from memory and a
couple different sources. 
To get the custom modeline, I typically use
http://xtiming.sourceforge.net/cgi-bin/xtiming.pl to get a close
modeline. If this doesn't work, I check the log file to verify the DCL
is within the range of the LX DCL. If it is and I get a black screen, I
verify the other values like HFL & VFL then move around the Horizontal
and Vertical Sync Time in the above website. Waving a rubber chicken or
other Voodoo incantations may help as well. :) 
I pulled this information from:
    http://ftp.utcluj.ro/pub/docs/how-to/mini-how-to/Modeline
    http://tldp.org/HOWTO/Framebuffer-HOWTO-18.html

For further reading on the subject of how Xorg get the timings:
    http://en.tldp.org/HOWTO/XFree86-Video-Timings-HOWTO/

I hope this helps.

Best Regards,

John Yoder

On Tue, 2009-04-28 at 10:51 +0800, wan michael wrote:
> in the file drivers/video/geode/lxfb_core.c
>  
> static struct fb_videomode geode_modedb[] __initdata = {
>         /* 640x480-60 */
>         { NULL, 60, 640, 480, 39682, 48, 8, 25, 2, 88, 2,
>           FB_SYNC_HOR_HIGH_ACT | FB_SYNC_VERT_HIGH_ACT,
>           FB_VMODE_NONINTERLACED, 0 },
>        ......
> }
>  
> now i want to add the mode of 800x480, but how to calculate these
> values. such as 
> 800x480-60, 800x480-70, 800x480-72, 800x480-80, 80x480-85, and so on.
> it is the case of changing the refresh frequency, what is the
> calculation? 
> 
> 
> 2009/4/26 wan michael <michalwan at gmail.com>
>         is it possible to be standard modeline like 800X600 through
>         adding 800x480 into geode driver, not just the custom modeline
>         in the xorg.conf ? 
>         
>         
>         another question, like 7" LCD display, they are commonly used
>         in the embedded device, like MID or handheld device, the most
>         resolution is 800x480. not like common PC, which can provide
>         much more higher resolution than 7" LCD display, such as
>         1024X768, and so on. So, when used for PC, it always selects
>         the best resolution,  and it can not do that for the embedded
>         device, for the reason of 7" LCD display supporting the most
>         high resolution is 800X480, if both of them can not match
>         well, the display will not be normal. so is there one way to
>         automatically match them, adapting to 800X480, not the higher?
>         
>         
>         2009/4/24 John Yoder <jtyoder at twny.net>
>         
>                 On Wed, 2009-04-22 at 14:20 +0800, wan michael wrote: 
>                 
>                 
>                 > hi
>                 >  
>                 > can the geode driver provide the mode 800x480? if
>                 > so, it can meet the 7' LCD display which is 800x480,
>                 > and not the standard modes on pc.
>                 >  
>                 >   
>                 > _______________________________________________
>                 > Xorg-driver-geode mailing list
>                 > Xorg-driver-geode at lists.x.org
>                 > http://lists.x.org/mailman/listinfo/xorg-driver-geode
>                 It should be able to provide the 800x480 mode.
>                 However, that will require a custom modeline in the
>                 xorg.cong. I would use one of the modeline calculators
>                 as a starting point. Whenever I need to provide custom
>                 modelines it takes a bit to get the dot clock
>                 frequency of the LX and Monitor to be correct, but not
>                 typically much of a problem.
>                 
>                 Best Regards,
>                 
>                 John Yoder 
>         
>