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

Johannes Bauer composed on 2015-09-06 11:45 (UTC+0200):

> not sure if this is the right newsgroup, but it's worth a shot.

> I've just installed Jessie i586 on an Intel Atom board. The board has
> has DVI output which is connected to a monitor.

> When booting, I can perfectly see the image during grub2 and also during
> early printk. Then comes the handoff to userspace (/bin/init), it
> executes some stuff (much too fast for me to see) and then I see some of
> these messages (they're copied from another problem report, but look
> exactly like this):

> [    2.123456] [drm:drm_edid_block_valid] *ERROR* EDID checksum is
> invalid, remainder is 43...

> This message comes about 3-4 times within 500ms (all guessed values, it
> all runs very fast), then the screen goes dark.

> My guess is that it's trying to do some font switching or frame buffer
> stuff, can't read what the monitor has to offer and switches to a weird
> setting. The system is alive (can ssh into it), but I'd like console
> output as well.

> So I've tried adding "nomodeset", "nofb" and "vga=normal" to my kernel
> cmdline, changed grub to GRUB_TERMINAL=console. The problem remains.

Grub2 complains about deprecation when I use it, but nevertheless, vga= seems
to do what it always did, at least on legacy x86: vga=788, vga=791 or
vga=794. I have no Atoms to try on. OTOH, vga=normal results in no
framebuffer device, so may be counter productive.

If the DVI is connected to a typical LCD, video= on cmdline ought to work:
e.g. video=1024x768@60 or equivalent to match your display's native mode. I
routinely use video= to override native mode on vttys to produce bigger text
than what the default framebuffer size produces using native mode.

> Can anyone's crystal ball reveal some clues on what's going on here and
> how I could fix that?

Is this exclusively a vtty problem, or both vtty and Xorg?

If only vttys, as I mentioned earlier, is plymouth installed? Does noplymouth
added to cmdline help? If it's not installed, does installing plymouth help?

IIRC, WRT Xorg, I've never been unable to work around bad EDID by providing a
simple /etc/X11/xorg.conf from which Xorg will calculate a desirable result.
A template:

"The wise are known for their understanding, and pleasant
words are persuasive." Proverbs 16:21 (New Living Translation)

 Team OS/2 ** Reg. Linux User #211409 ** a11y rocks!

Felix Miata  ***  http://fm.no-ip.com/

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