Atombios table editor: Screen that ONLY supports 1280x800 resolution

Ricardo Ribalda Delgado ricardo.ribalda at
Wed Apr 24 07:28:52 PDT 2013

Hello Alex

The panel has an EDID available. If I probe the i2c lines I can see
that the system is reading it. But it is either ignoring it or using
it wrongly. I have verified the edid contents with parse-edid.

I have also probed the pixel clock and the measured frequency is
25MHz (std. VGA), when the panel only supports frequencies from
67.5MHz to 74.5MHz (typ. 71MHz).

My theory is that the vbios doesn't know how to handle the panel mode
and defaults to another resolution.

I don't expect much help from my oem. It is more or less a custom
setup that they wont support.

I believe that for the development of the OSS driver tools like
AtomDis have been used, so I was hoping that there wes an equivalent
tool for "assembling" the bios back once modified. I would expect that
the vbios would have a number of csums.

Any other mean of debugging the vbios would be highly appreciated, I
am now on a dead end :(.


root at qt5022:~# cat
/sys/devices/pci0000:00/0000:00:01.0/drm/card0/card0-DP-1/edid  |
parse-edid: parse-edid version 2.0.0
parse-edid: EDID checksum passed.

# EDID version 1 revision 3
Section "Monitor"
# Block type: 2:0 3:fc
Identifier "LD101WX1-SL01"
VendorName "LGD"
ModelName "LD101WX1-SL01"
# Block type: 2:0 3:fc
# Block type: 2:0 3:fd
HorizSync 49-50
VertRefresh 53-63
# Max dot clock (video bandwidth) 70 MHz
# Block type: 2:0 3:fe
# DPMS capabilities: Active off:no  Suspend:no  Standby:no

Mode "1280x800" # vfreq 59.982Hz, hfreq 49.306kHz
DotClock 71.000000
HTimings 1280 1328 1360 1440
VTimings 800 802 808 822
Flags "-HSync" "-VSync"
# Block type: 2:0 3:fc
# Block type: 2:0 3:fd
# Block type: 2:0 3:fe

ps: I have tried also to hack the Max dot clock to 80... with sameresults

On Wed, Apr 24, 2013 at 3:25 PM, Alex Deucher <alexdeucher at> wrote:
> You should talk to your oem.  The vbios always attempts to set the
> native timing of the panel if an EDID is available.  Note that the
> standard vesa modes may not include this mode, but the vbios will use
> the hw scalers to scale from the native mode to whatever vesa mode you
> are using.
> Alex
> On Tue, Apr 23, 2013 at 12:20 PM, Ricardo Ribalda Delgado
> <ricardo.ribalda at> wrote:
>> Hi
>> I have screen that only works at 1280x800. Unfortunately, that
>> modeline is not on the bios ModeTimings table, so the bios tries to
>> set the screen at a different resolution, giving out a consistent
>> black image ;). Once linux is booted and X is started I get a proper
>> output.
>> I would like to add the timings of my screen to my video bios. Is
>> there any tool to do this?
>> If not, there is any tool that can recalculate the crc of a manually
>> modified video bios?
>> Thanks for your help!
>> --
>> Ricardo Ribalda
>> _______________________________________________
>> xorg-driver-ati mailing list
>> xorg-driver-ati at

Ricardo Ribalda

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