Bug#476575: i855: no VGA output unless VGA connected at boot
Will Thompson wrote:
> If I boot my laptop (a Toshiba SA55) without an external monitor
> attached to the VGA port, and subsequently try to enable the VGA output
> with xrandr, xrandr seems to believe it has succeeded but no image is
> ever drawn upon the external monitor.
>
See below.
> If I boot with the external monitor attached, the boot sequence is
> displayed exclusively upon it, then X shows up on both the external
> display at its full resolution and on the internal display, truncated to
> 1024x768.
>
This looks normal to me.
> Upon running `xrandr --output VGA --auto`, the desktop stretches to
> 1650x1050, the top-left 1024x768-sized corner is displayed on the laptop
> panel, and the external monitor stays blank (claiming "no signal" if
> cajoled). Running xrandr while in this state produces:
>
> Screen 0: minimum 320 x 200, current 1680 x 1050, maximum 2048 x 2048
> VGA connected 1680x1050+0+0 (normal left inverted right x axis y axis) 473mm x 296mm
> 1680x1050 60.0*+
>
Is this the exact mode supported by your monitor? Can you compare the
Modeline issued in Xorg.0.log for this resolution and refresh when
booting with VGA plugged (i.e. when 1680x1050@60 works) and when booting
without and plugging VGA later (i.e. when 1680x1050@60 does not work)?
I think I've seen other people report similar problems but I can't find
them.
> Closing the laptop lid apparently disables the panel's
> backlight, but the image is still drawn on the panel; the backlight does
> not turn back on when the lid is re-opened.
> Running `xrandr --output VGA --off` does the right thing; `xrandr
> -output VGA --auto` restores external output. So, having booted with
> the external screen attached everything works, modulo the backlight
> being permanently off if the lid has ever been closed. (Should I file a
> separate bug about this?)
>
I don't want to mix different problems here, so I'd rather have another
bug about this.
> Section "Monitor"
> Identifier "Generic Monitor"
> Option "DPMS"
> HorizSync 30-70
> VertRefresh 50-160
> EndSection
>
Just in case, you might want to remove HorizSync and VertRefresh above.
And the "Modes" line below may be dropped too.
> Section "Screen"
> Identifier "Default Screen"
> Device "Intel Corporation 82852/855GM Integrated Graphics Device"
> Monitor "Generic Monitor"
> DefaultDepth 24
>
> SubSection "Display"
> Depth 24
> Modes "1680x1050" "1600x1200" "1280x1024" "1024x768" "800x600" "640x480"
> Virtual 2048 2048
> EndSubSection
> EndSection
>
Brice
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