From: Robert Morell <rmorell@nvidia.com>
To: Keith Packard <keithp@keithp.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
DRI mailing list <dri-devel@lists.freedesktop.org>
Subject: Re: "EDID checksum is invalid"
Date: Tue, 6 Jan 2015 22:21:09 -0800 [thread overview]
Message-ID: <20150107062109.GA32123@morell.nvidia.com> (raw)
In-Reply-To: <86387nrum9.fsf@hiro.keithp.com>
On Tue, Jan 06, 2015 at 10:07:58PM -0800, Keith Packard wrote:
> * PGP Signed by an unknown key
>
> Linus Torvalds <torvalds@linux-foundation.org> writes:
>
> > it looks like the beginning is the same, but then it just turns to all
> > ones at a random point (even *within* a byte).
>
> Looks like the EDID ROM is dropping off the i2c bus in the middle of the
> transfer. Wonder if it's being 'clever' if things go too slowly at some
> point, or if there's a bug in the DDC code that's in use.
FWIW, I've seen that exact symptom on some monitors when the +5V pin on
the DVI or HDMI cable from the GPU isn't enabled (or isn't providing
enough current). Some monitors power the i2c/edid/DDC logic from that
+5V either exclusively or when in the DPMS off state, and the i2c chip
will just stop responding after a few cycles if not provided sufficient
power.
- Robert
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next prev parent reply other threads:[~2015-01-07 6:21 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-07 2:01 "EDID checksum is invalid" Linus Torvalds
2015-01-07 6:07 ` Keith Packard
2015-01-07 6:21 ` Robert Morell [this message]
2015-01-07 6:42 ` Keith Packard
2015-01-07 17:07 ` Linus Torvalds
2015-01-07 17:51 ` Daniel Vetter
2015-01-07 18:03 ` Linus Torvalds
2015-01-08 7:05 ` Keith Packard
2015-01-07 7:32 ` Daniel Vetter
2015-01-07 17:51 ` Linus Torvalds
2015-01-07 20:06 ` Daniel Vetter
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