[Openchrome-devel] [Bug 91966] No signal to monitor with X and openchrome using VX855 chipset graphics

bugzilla-daemon at freedesktop.org bugzilla-daemon at freedesktop.org
Wed Feb 24 04:11:48 UTC 2016


--- Comment #216 from Kevin Brace <kevinbrace at gmx.com> ---
(In reply to Justin Chevrier from comment #211)

Hi Justin,

> >     Regarding VX900's native support for DVI (I am assuming that VX900
> > chipset actually has an integrated TMDS transmitter.), I will make a patch
> > that will temporarily activate LCD screen for HP T5550 or disable the use of
> > this weird table for certain models with integrated TMDS transmitters like
> > VX900 chipset.
> > I hope this will make OpenChrome to run through the code that detects DVI
> > using its integrated TMDS transmitter.
> I tweaked the T5550 entry (I've attached the patch) and as you suspected
> enabling the LCD device allowed the monitor connected via DVI to be detected
> and function via the DVI-I port (log attached). The DVI-D connector remained
> non-functional. The monitor connected with a VGA cable via the DVI to VGA
> adapter was still detected, but no longer displayed anything (log attached).

Well, at least there is some good news that the weird known device table was
the culprit as I have guessed.
It now appears that DVI-I's DVI portion comes from VX900's integrated TMDS
transmitter, and VT1632A TMDS transmitter chip is connected to I2C bus 3.
When the code to support VT1632A was donated, it had a strange assumption that
VT1632A detection was done only when P4M800 Pro, VN800, or CN700 chipset is
I took out this assumption, but to complicate the situation, I2C bus 3 is not a
hardware based I2C implementation like I2C bus 1 and 2.
I do not know how proven the I2C bus 3 controlling code really is.
If your thin client's VT1632A was connected to I2C bus 2, it would have been a
different story, as I have seen 2 different people able to get OpenChrome to
recognize VT1632A on I2C bus 2 (i.e., OpenChrome is able to get vendor ID match
on I2C bus 2) recently.
I will likely develop a patch that will use look into what is being sent over
I2C bus 3 since OpenChrome is not getting vendor ID match over I2C bus 3 in
your situation.
Without vendor ID match, OpenChrome will assume that VT1632A is not connected.
    As for the DVI to VGA adapter not working well, again, that is bad.
I will try to think of a something for you to try in the next few days.

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