[Openchrome-devel] [Bug 96397] legacy modesetting removal breaks CLE266

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=96397

--- Comment #12 from Kevin Brace <kevinbrace at gmx.com> ---


(In reply to Xavier Bachelot from comment #9)

Hi Xavier,

> I've experimented a bit more with this. Setting all of 3d5 6a, 6b and 6c to
> 0x00 restores the display with 0.4.169.

I will have to ask the question, what do you precisely mean "restores the
display with 0.4.169?"
Does the screen suddenly start working properly at 1920 X 1080 resolution with
Version 0.4.169 if 3X5.6A, 3X5.6B, and 3X5.6C are all set to 0x00?
    Now, comparing the 2 files.
This is from the non-working version (I assume OpenChrome Version 0.4.169.).

________________________________________________________________
. . .
    0x6a = 0x80 (Second Display Channel and LCD Enable)
    0x6b = 0x84 (Channel 1 and 2 Clock Mode Selection)
    0x6c = 0x01 (TV Clock Control)
. . .
________________________________________________________________


This is from the working version (OpenChrome Version 0.4.0 with your patch to
revert the code change.).

________________________________________________________________
. . .
    0x6a = 0x00 (Second Display Channel and LCD Enable)
    0x6b = 0x00 (Channel 1 and 2 Clock Mode Selection)
    0x6c = 0x00 (TV Clock Control)
. . .
________________________________________________________________


I personally think 3X5.6C is not related to this bug (it is related to TV clock
control), so we should leave that register alone.
That means 3X5.6A and 3X5.6B are contributing to the problem.
For now, I will ignore 3X5.6A.
This is due to the fact that 3X5.6A is mostly related to IGA2 (secondary
display controller), and in your case, it is not running.
Looking at CX700 UniChrome Pro II programming guide, I suspect 3X5.6B[7:6] -
First Display Channel Clock Mode Selection might be contributing to the
problem.
Here is an edited version of 3X5.6B.

________________________________________________________________
3X5.6B Channel 1 and 2 Clock Mode Selection

3X5.6B[7:6] - First Display Channel Clock Mode Selection
              0x: Normal
              1x: Division by 2
. . .
________________________________________________________________


For stock OpenChrome Version 0.4.169, 3X5.6B is 0x84.
This implies that IGA1 clock mode is set to division by 2 mode.
Within OpenChrome, it appears that IGA1 is set to division by 2 mode only when
TV out is used (i.e., VT1622).

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