Completely ignore EDID for KMS, use user-supplied kernel param (video=)?

Alex Deucher alexdeucher at
Mon Nov 22 23:00:51 PST 2010

On Mon, Nov 22, 2010 at 11:02 PM, Paul Sokolovsky <pmiscml at> wrote:
> Hello,
> There're cases when EDID may be present, but be just severely (or
> seemingly) broken. Is it possible to completely and unconditionally
> ignore any EDID info for KMS, and instead use user-supplied parameters?
> I googled the following message:
> which suggested that it's possible, but I don't have any effect doing
> it myself.
> It's also very hard to diagnose these issues. For example, mode
> selection is driven by EDID, but there're whole 0 occurances of that
> string in kernel dmesg. Passing drm.debug=1 starts to dump some
> internal registers, but still no hints which and why mode was selected.
> My specific issue is that there's an LVDS (of MSI X410/X430 notebook)
> which has right dimensions and refresh rate, but wrong, if not say
> unrelated, clock settings. The end result is that there's tearing-off,
> broken sync like on an old dying TV. More details are at
> . That's on
> 2.6.35 (stock Ubuntu 10.10 kernel). I was able to set CVT timings on X
> which gave stable picture, but no luck persuading kernel to do the same
> (I used video=LVDS-1:1366x768M at 60 param, also tried more conventional
> modes like 1024x768).
> I'd appreciate any hints.

Assuming your laptop contains a radeon, the panel timing comes from a
table in the vbios.  The timing problem is most likely not due to an
EDID problem, but to pll dividers that that panel doesn't like.  Try
booting with radeon.new_pll=0 on the kernel command line or try kernel


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