[SOLVED] Stretch: how to disable the modesetting DDX driver?

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[SOLVED] Stretch: how to disable the modesetting DDX driver?

Postby zenlord » 2019-01-01 12:51

Hi,
I maintain a few NUC's (of multiple generations) and one of the final hurdles all of my users report is a slight flickering when updating tasks and events in Gnome Evolution.
Usually I install xserver-xorg-video-intel on all my machines and was under the impression that the intel DDX driver was causing this flickering, so I removed it to see whether the modesetting DDX driver would improve things. It didn't, but as it turns out: reinstalling the intel DDX (and adding a Device section to xorg.conf.d/20-intel.conf) does not make Xorg choose the intel DDX driver...
How can I disable/blacklist/block the modesetting DDX driver?

Some background info:
Code: Select all
$ inxi -G
Graphics:  Card: Intel HD Graphics 5500
           Display Server: X.Org 1.19.2 drivers: modesetting (unloaded: fbdev,vesa)
           Resolution: 1920x1200@59.95hz
           GLX Renderer: Mesa DRI Intel HD Graphics 5500 (Broadwell GT2)
           GLX Version: 3.0 Mesa 13.0.6

# grep -i modesetting /var/log/Xorg.0.log
[     2.415] (==) Matched modesetting as autoconfigured driver 0
[     2.415] (II) LoadModule: "modesetting"
[     2.415] (II) Loading /usr/lib/xorg/modules/drivers/modesetting_drv.so
[     2.416] (II) Module modesetting: vendor="X.Org Foundation"
[     2.417] (II) modesetting: Driver for Modesetting Kernel Drivers: kms

# cat /etc/X11/xorg.conf.d/20-intel.conf
Section "Device"
  Identifier   "Intel Graphics"
  Driver   "intel"
  Option   "AccelMethod" "sna"
  Option   "TearFree" "true"
EndSection

# cat /etc/modprobe.d/i915.conf
options i915 fastboot=1 enable_fbc=1 enable_psr=0

# grep LINUX_DEFAULT /etc/default/grub
GRUB_CMDLINE_LINUX_DEFAULT="quiet acpi_osi='Linux'"

Thx,
Vincent
Last edited by zenlord on 2019-01-01 14:04, edited 1 time in total.
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Re: Stretch (w/ BPO kernel): how to disable modesetting DDX?

Postby Segfault » 2019-01-01 13:39

Please drop the whole Xorg log into a pastebin.
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Re: Stretch (w/ BPO kernel): how to disable modesetting DDX?

Postby Head_on_a_Stick » 2019-01-01 13:49

zenlord wrote:
Code: Select all
# cat /etc/X11/xorg.conf.d/20-intel.conf

Do you have any other configuration files in /etc/X11/xorg.conf.d (or elsewhere) that may be changing the driver — those files are parsed in lexicographical order so a "higher" named file could over-write that configuration.

In my experience Debian stable will auto-select xserver-xorg-video-intel in preference to the modesetting DDX driver if the package is installed, there should be no need for any Xorg configuration files.

The TearFree option may help with the flickering though ;)
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Re: Stretch (w/ BPO kernel): how to disable modesetting DDX?

Postby zenlord » 2019-01-01 14:03

Thank you for your fast reply, @segfault and @Head_on_a_stick!

While looking for the various Xorg.0.logs on my systems, it struck me that the one in /var/log/ is not the most recent one, and probably inxi is retrieving it's information from that file. The log in $XDG_DATA_DIR ($HOME/.local/share/ for most distributions, but /var/data/users in my case because our profiles are hosted on NFS) shows that indeed the intel driver is loaded.

For future reference:
* Xorg logs can be found in $XDG_DATA_DIR/xorg/
* Disabling the modesetting DDX driver is (still :)) simply a matter of installing xserver-xorg-video-intel and adding a Device section to /etc/X11/xorg.conf.d/20-intel.conf
* Do not trust the inxi tool

I'll mark this topic as solved. Thank you!
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Re: [SOLVED] Stretch: how to disable the modesetting DDX dri

Postby Head_on_a_Stick » 2019-01-01 14:11

~/.local/share/xorg is used if the X server is being run as the normal user (via GDM3 or `startx` from a console login) rather than /var/log, which is still used if X is run as root (under LightDM, for example).
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