Wrong DDC information for external monitor with i810

[Alan Hourihane]

On Thu, 2006-09-14 at 08:54 +0000, Christoph Burghardt wrote:
> Hi,
> 
> i have a Fujitsu P5020D with an Intel 855GM chip. I'm trying to get my
> external monitor working.  It gets detected with DDC:
> 
> (II) I810(0): Manufacturer: @HA  Model: 101  Serial#: 16843009
> (II) I810(0): Year: 2004  Week: 41
> (II) I810(0): EDID Version: 1.2
> (II) I810(0): Analog Display Input,  Input Voltage Level: 0.700/0.700 V
> (II) I810(0): Sync:  Separate
> (II) I810(0): Max H-Image Size [cm]: horiz.: 30  vert.: 23
> (II) I810(0): Gamma: 2.51
> (II) I810(0): DPMS capabilities: StandBy Suspend Off; RGB/Color Display
> (II) I810(0): First detailed timing is preferred mode
> (II) I810(0): redX: 0.622 redY: 0.307   greenX: 0.271 greenY: 0.555
> (II) I810(0): blueX: 0.115 blueY: 0.077   whiteX: 0.282 whiteY: 0.299
> (II) I810(0): Supported VESA Video Modes:
> (II) I810(0): 720x400 at 70Hz
> (II) I810(0): 640x480 at 60Hz
> (II) I810(0): 640x480 at 67Hz
> (II) I810(0): 640x480 at 72Hz
> (II) I810(0): 640x480 at 75Hz
> (II) I810(0): 800x600 at 56Hz
> (II) I810(0): 800x600 at 60Hz
> (II) I810(0): 800x600 at 72Hz
> (II) I810(0): 800x600 at 75Hz
> (II) I810(0): 832x624 at 75Hz
> (II) I810(0): 1024x768 at 60Hz
> (II) I810(0): 1024x768 at 70Hz
> (II) I810(0): 1024x768 at 75Hz
> (II) I810(0): Manufacturer's mask: 0
> (II) I810(0): Supported Future Video Modes:
> (II) I810(0): #0: hsize: 1024  vsize 768  refresh: 72  vid: 19553
> (II) I810(0): #1: hsize: 800  vsize 600  refresh: 70  vid: 19013
> (II) I810(0): Supported additional Video Mode:
> (II) I810(0): clock: 81.0 MHz   Image Size:  0 x 0 mm
> (II) I810(0): h_active: 1280  h_sync: 1328  h_sync_end 1440 h_blank_end 1688 h_border: 0
> (II) I810(0): v_active: 768  v_sync: 769  v_sync_end 772 v_blanking: 800 v_border: 0
> (II) I810(0): Ranges: V min: 60  V max: 75 Hz, H min: 31  H max: 60 kHz, PixClock max 80 MHz
> (II) I810(0): Monitor name: WXGA
> 
> Based on this, i've inserted a modeline:
> 
> Section "Monitor"
>         Identifier      "TV"
>         Option          "DPMS"
>         Option          "VertRefresh"   "60-75"
>         Option          "HorizSync"     "31-60"
>         Option          "Modeline" "1280x768 81   1280 1368 1440 1688   768 769 772 800  -hsync -vsync"
> EndSection
> 
> and i want to get this monitor working with 1280x768
> 
> Section "Screen"
>         Identifier      "Extern Screen"
>         Device          "i810-A"
>         Monitor         "TV"
>         DefaultDepth    24
>         SubSection "Display"
>                 Viewport        0       0
>                 Depth           8
>                 Modes           "1280x768"
>         EndSubSection
>         SubSection "Display"
>                 Viewport        0       0
>                 Depth           15
>                 Modes           "1280x768"
>         EndSubSection
>         SubSection "Display"
>                 Viewport        0       0
>                 Depth           16
>                 Modes           "1280x768"
>         EndSubSection
>         SubSection "Display"
>                 Viewport        0       0
>                 Depth           24
>                 Modes           "1280x768"
>         EndSubSection
> EndSection
> 
> 
> I've already patched with i915resolution the vesa modes but it ends up
> with:
> 
> *(WW) (1280x768,TV) mode clock 80.14MHz exceeds DDC maximum 80MHz
> 
> So xorg ignores my modeline and ignores the extended information from
> the monitor. If i set NoDDC, then i only get 640x480. I am out of ideas and would greatly appreciate any
> help you could give me.
> 

Your monitor's DDC is broken. See this line....

(II) I810(0): clock: 81.0 MHz   Image Size:  0 x 0 mm

and then this....

(II) I810(0): Ranges: V min: 60  V max: 75 Hz, H min: 31  H max: 60 kHz,
PixClock max 80 MHz

The modeline requires 81.0MHz (or in the calculated case 80.14MHz), but
the monitor's DDC says it's got a maximum of 80.0MHz. Therefore the mode
is rejected.

Only thing you can do for now is disable DDC, with Option "NoDDC".

For future versions if any modes are explicitly listed, then we should
allow them regardless of the max pixclock.

Alan.