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Re: Screen goes blank after "EDID checksum is invalid" errors

On 2015-09-06 12:31 +0200, Stephen Powell wrote:

> On Sun, 06 Sep 2015 05:45:30 -0400 (EDT), Johannes Bauer wrote:
>> [drm:drm_edid_block_valid] *ERROR* EDID checksum is invalid, remainder is 43
> Some monitors have invalid EDID checksums.  Blame the manufacturer.
> Windows is more tolerant of EDID checksum errors than Linux is.
> If switching monitors solves your problem, then a bona fide EDID checksum
> error in the hardware is probably to blame.  If you're willing to
> build a custom kernel, you may be able to circumvent the problem by applying a
> patch.  See my kernel-building web page:
>    http://users.wowway.com/~zlinuxman/Kernel.htm
> In "Step 7: Patch the kernel", there is a specific example of how to apply
> this patch.  Basically, it allows you to tell the kernel to ignore EDID
> check sum errors by using the following setting in a file with the extension
> of ".conf" under /etc/modprobe.d:
>    options drm edid_strict=0
> This may allow you to use your faulty monitor anyway.  Good luck.

I don't think this is a very good idea in this case, the EDID of
Johannes' monitor seems to be very broken (almost all bytes are 0xff).
Rather than patching the kernel to not complain about that, it is
probably better to supply valid EDID data via the
drm_kms_helper.edid_firmware option.

The downside of this approach is that you have to supply the EDID
file, there are several under Documentation/EDID/ in the kernel
source (assembly source and a Makefile).


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