[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
Tue Feb 23 03:33:52 UTC 2016


--- Comment #208 from Kevin Brace <kevinbrace at gmx.com> ---
(In reply to Justin Chevrier from comment #204)

Hi Justin,

> I have some HP T5550 (VX900) thin clients that used to previously work under
> the 0.2.x branch, but stopped working under 0.3.x with the same issue
> described in this bug (no displays are detected). This thin client has 2 DVI
> ports, a DVI-I and a DVI-D. Up to this point no monitors are detected using
> either DVI port with DVI cable or with a DVI-I to VGA adapter and connected
> via VGA cable. The distribution I'm using for testing is Thinstation (5.3). 
> I have pulled the latest code from GIT and have applied the latest VGA
> detection patch ( attachment 121872 [details] [review] ) on top. I'm happy
> to report that with the latest GIT pull and VGA patch applied the monitor is
> detected and functional via VGA, but unfortunately not on either DVI port
> (the same monitor is used in all tests). The driver has been built with
> debugging and via_regs_dump enabled. I am attaching 3 logs.
> DVI on the DVI-D port
> DVI on the DVI-I port
> VGA on the DVI-I port with VGA adapter
> Keep me posted if I can assist further!

Thank you very much for testing the patch.
You did the testing the way I would have done it myself, and posted the exact
log files I wanted (i.e., DVI-D, DVI from DVI-I, and VGA from DVI-I).
Interesting that I2C bus 1 is not used, and instead DVI-I is connected to I2C
bus 2 in HP T5550 (Hence, the patch partially works since the code will now
look for I2C bus 2 when detecting a VGA monitor.).
That being said, I feel bad that DVI on I2C bus 3 is not working.
That code was donated in early 2015, but I suspect that it did not really go
through rigorous testing before getting incorporated into the master branch.


Someone else reported a bug (crash) with the donated code, so with the help of
the reporter, we were able to fix the bug.


That being said, the original reporter of this bug, Christopher, was able to
get the VT1632A detected on his thin client (He used an older version patch.
The one you tried and the patch Christopher tried are essentially functionally


In his system, VT1632A is on I2C bus 2.
I do not mean to make fun of Christopher, but he frequently runs into equipment
trouble (^_^), so this has slowed down the debugging effort (Don't take it
personally, Christopher!).
I am glad that you appear to have full control of the local storage of your
thin client (i.e., you are able to install some kind of Linux based OS on the
SSD), so this might speed up the debugging effort.
    Currently, OpenChrome suffers from what I call, "weird known device table"
problem, and this weird table gives hints on which display devices to detect.
This is what the table looks like.

    /*** VX900 ***/
    {"Simmtronics SIMM-PC VX900i",            VIA_VX900,   0x1019, 0x3126,
    {"ECS VX900-I",                           VIA_VX900,   0x1019, 0x7C8E,
    {"Foxconn L740",                          VIA_VX900,   0x105B, 0x0CFD,
    {"HP T5550 Thin Client",                  VIA_VX900,   0x1106, 0x7122,
    {"Biostar Viotech 3200+",                 VIA_VX900,   0x1565, 0x120A,
    {"ASRock PV530",                          VIA_VX900,   0x1849, 0x7122,
    {"Fujitsu Futro A300",                    VIA_VX900,   0xA0A0, 0x080F,

    /* keep this */
    {NULL,                                    VIA_UNKNOWN, 0x0000, 0x0000,

Yes, your thin client is in the table, but for some reason, the previous
developers who made this table in the first place marked HP T5550 as only
supporting VGA.
Please note that I am not a fan of this weird table, and the use of it will be
discontinued in the near future (not with the upcoming Version 0.3.4).
    It is not totally clear if VX900 natively supports DVI.
The register bits used to handle DVI are "reserved" in VX900 (Source: VX900
Series Chrome9 HD Open Graphics Programming Manual).
    This is what I will do.
I will commit the patch you tested to the repository since it fixes the DVI to
VGA adapter bug.
I finally got confirmation that the lack of the use of I2C bus 2 was the root
cause of DVI to VGA adapter display bug (I suspected this since early January,
but was not able to get a confirmation due to Christopher's equipment
This feature was working in OpenChrome Version 0.2.904, and OpenChrome Version
0.2.904 was used by Ubuntu 10.04 LTS and 12.04 LTS.
I personally want Canonical to retire OpenChrome Version 0.2.904, and hope that
the commit of this patch will do it.
    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.

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