[Openchrome-devel] [Bug 95146] No mouse cursor (invisible) with DVI cable

bugzilla-daemon at freedesktop.org bugzilla-daemon at freedesktop.org
Fri Jul 1 05:49:10 UTC 2016


Kevin Brace <kevinbrace at gmx.com> changed:

           What    |Removed                     |Added
                 CC|                            |kevinbrace at gmx.com

--- Comment #4 from Kevin Brace <kevinbrace at gmx.com> ---
Hi Zong,

I tried to fix the bug with Eric Kudzin the other day, but apparently the fix
does not work.


Please note that the patch will likely not work.
It appears that CN700's video display engine and later model's (i.e., P4M890
and later) video display engine are different, hence, the code only works as
long as the user is using VGA only, and VGA is coming from IGA1 (display
controller #1).
It appears that VIA updated the video display engine around P4M890 to CME from
the older CLE engine.
Based on how the patch did not work, I think CN700 contains the older CLE
    When James Simmons worked on the new DRM module supporting KMS, he probably
simply copied the code from OpenChrome UMS code to the KMS portion of the new
DRM module.
He probably did not know that the cursor will not work in CN700 when using IGA2
(i.e., DVI from VT1632A).
When I tested the fix with Eric using his Wyse Vx0 thin client, one monitor can
display the cursor (technically, hardware icon or HI), but the other one
I managed to get DVI working in Vx0 by tinkering with 3X5.96 via (no pun
intended) via_regs_dump tool.
It now appears that Wyse Vx0's DVI chip (VT1632A) is connected to DVP0 (Digital
Video Port 0).
The register to control this is located at 3X5.96.
I will call this register Digital Video Port 0 Function Select 0.
The bit fields appear to be identical to 3X5.9B (Digital Video Port 1 Function
Select 0).
Please note that none of the OGPM (Open Graphics Programming Manual) documents
VIA Technologies released mentions DVP0 since DVP0 was discontinued starting
with CX700 chipset.
3X5.96 is reserved starting with CX700 chipset.
In order to get IGA2 to be the source of DVP0, set bit 4 to 1.
Keep all the other fields intact.
We managed to get DVI working this way, and I may be able to put the DVP0
related fix in the Version 0.5.
As for the cursor issue, software cursor may have to be turned on all the time
for CN700 and older chipsets since HI does not seem to work when IGA1 and IGA2
are running simultaneously (i.e., VGA + DVI RandR situation).

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