[Openchrome-devel] [Bug 100679] Garbled graphics when resuming from standby

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=100679

--- Comment #46 from Kevin Brace <kevinbrace at gmx.com> ---
Hi Marty,

(In reply to Marty from comment #45)
> Hi Kevin,
> 
> Congratulations, this brought some progress:
> 

Yeah, I did work on the major code overhaul (i.e., new display device detection
and initialization method) partially to fix the problem you encountered, but
that being said, I was planning to do this for a while.
I did not make any commits between April 28th, 2017 to May 18th, 2017 because I
was working on the updated code, and this is a relatively long period of not
committing any code, at least in my standards.
The new code now probes for the attached display devices that can be identified
by some means (i.e., I2C bus scan of the vendor ID and device ID) before
assigning other devices that are more or less always available (i.e., VGA).
The code also leaves hints about which display channel the display is attached
to, and this information ultimately comes from the probing.
Furthermore, I2C bus is also assigned based on probing results, and because of
this, the code has regained the capacity to obtain EDID for FP via I2C bus for
FP screen resolution determination (This feature was disabled in Version 0.6.).


> 1. Switching to other tty consoles (e.g. Ctrl-Alt-F1) works now, but only
> when I enable the graphical terminal in /etc/default/grub.
> That means I have to comment the line "GRUB_TERMINAL=console". In the
> original Ubuntu 14.04 driver it was vice-versa: Only be uncommenting this
> line the switch to other consoles worked.
> 

I think the VT implementation when used in conjunction with a non-KMS (Kernel
Mode Setting) DDX device driver is a disaster, and it is my opinion that this
will never really be fixed.
All I have been trying to do with the OpenChrome DDX is not to interfere or
sabotage VT switch, and based on how the VT switch is implemented, what we have
right now is probably as good as it will get.
The VT behavior appears highly dependent on the VGA BIOS (VBE or VESA BIOS
Extension portion of VGA BIOS) and / or GRUB version, and it also differs
wildly from platform to platform.
Furthermore, the behavior can be quite different between two different
computers with the same chipset (HP 2133 vs. MSI VR321; both have VN896
chipset).
Other than not trying to sabotage the VT switch, there is little DDX can do, at
least with the current antiquated UMS (User Mode Setting) DDX code.


> 2. Resuming from standby works now! There is one little hitch: After resume
> the lock screen appears correctly and I can log-in. But if I then lock the
> screen again, it stays black. But I can blindly log-in and the normal screen
> restores correctly.
> 

This may not really be an OpenChrome issue.
I do not really use Lubuntu 14.04, and the reason for not really wanting to use
Lubuntu 14.04 is that I had many issues with how the power management control
is implemented on Lubuntu 14.04.
For example, I cannot alter the power button behavior on Lubuntu 14.04.
The thing about Linux distributions is that the developers will NEVER fix
anything after the code is released.
All of those .1, .2 releases (i.e., Lubuntu 14.04.1, 14.04.2, etc.) really do
not fix anything other than security issues.
Many substantial usability issues might get fixed if you move to a newer
version or maybe not.
For this reason, I use Xubuntu 14.04 for the drm-openchrome development, and
power management control works for the most part.
That being said, I had to disable lightdm password prompt since it appears to
cause several issues when I test drm-openchrome code.


> 3. The color depth seems to be lower than with the original driver. I cannot
> say what color depth is used now but I can see it from color steps in the
> background image.
> 
> Best regards,
> Marty

You may have to upload a screen shot of the screen if it helps to see what is
going on, but it is possible that gamma correction is not being disabled
properly (or the color palette is getting messed up) after resuming.
It is also possible that FP port signal adjustment parameter is off after
resume.
Marty, you may have to do previously discussed the dump of the registers again.

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