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#1 2013-03-02 08:13:22

jghodd
Member
Registered: 2013-02-10
Posts: 52

Problem syncing gma500 in native res using modesetting driver

I have a D2500/GMA3600 netbook running Arch and I'm having a problem getting the screen to sync properly when using the modesetting (or fbdev) xorg driver. The LVDS screen supports 1024x600 as its native resolution, and the Windows 7 installation I have on another partition uses this resolution without any issue.

I can run with VESA @ 800x600, but this resolution is stretched and doesn't look right, not to mention the performance is lousy. I've read all over the place that the gma500_gfx driver should be able to run at native resolution just using the modesetting driver - and it does. Kinda. The problem is that I can;t get the screen to sync properly.

I've checked my modeline setting against the edid blob I scavenged from my windows 7 registry, and even without specifying it in my xorg.conf file, xorg is grabbing it just fine obviously using the same edid, according to my Xorg.0.log file. I've gone so far as to install the windows edid blob in firmware/edid and explicitly load it via the kernel command line, and provide the specific modeline that matches. I've even hunted done several other modelines and created edid blobs to match them using phoenix in windows, and confirming them using the read-edid ubuntu package. Nothing fixes the sync problem.

What I'm seeing is 1) the bottom 2/3 of the KDM login screen is shunted upwards by about 1/4 inch overlapping the top 1/3 of the screen, with a 1/4 inch band of noise across the bottom, and the bottom 2/3 flickers badly; 2) the bottom of the openbox screen flickers badly and any apps opened to max have their tops replicated about 10 times down the screen; 3) KDE is... well just bad - the top 60% of the screen is the whole screen with the middle squished to nothing and the bottom 40% of the screen is a replication of the top of the screen with the bottom missing, and both the top and bottom have a 1/4 inch band of noise running across the screen.

I have found that I can make the KDM and openbox screens "appear" to behave better by setting the gamma correction to 0.8, but even then, appearances can be deceiving - the problem is still there when you move a window down into the areas where the problems used to appear and maximized apps still do their funky replicating act.

I've tried setting nomodeset on the kernel command line, downgrading the kernel to 3.6, using fbdev vs. modesetting, passing mem=1920mb to the kernel, and at this point have run out of ideas. I'd have thought that if xorg was using the same graphics timing settings as the windows driver, that it should be just as stable, but obviously not. I'm a little discouraged that others with the same chipset have had no problem using the modesetting driver and yet I can't get it to work despite making sure that the timing details match up with a known stable operating environment on the same system.

Can anyone offer any suggestions (other than the obvious "shoulda got a different chipset" which is hilarious, but doesn't help)?

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#2 2013-03-06 20:06:57

jghodd
Member
Registered: 2013-02-10
Posts: 52

Re: Problem syncing gma500 in native res using modesetting driver

OK. I'm finally able to get native resolution using uvesafb/v86d and 915resolution. The performance isn't bad and the display is stable. Glxgears is showing over 100 FPS and video streams nicely in full screen.

I provided a new patch for 915resolution-static to handle the GMA3600 and you can find the packages and PKGBUILD archives at http://bluestarlinux.org/index.php?acti … ds;cat=312. I also wrote out configuration instructions in an article there as well, although the Arch Wiki instructions are probably more complete and better written (https://wiki.archlinux.org/index.php/Uvesafb).

Anyone else who has been experiencing the same problem with their gma3600 would well be advised to go this route. I've searched the internet over and found nothing that works properly using the xorg modesetting or fbdev drivers. I even built the cedarview_gfx kernel driver and its associated drm modules provided by thomas001 (http://gh.codehum.com/thomas001/cedarview-drm) and still couldn't acheive more than an 800x600 resolution with a stable display.

Hope that provides some much needed help for some folks.

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#3 2013-03-07 09:37:45

jghodd
Member
Registered: 2013-02-10
Posts: 52

Re: Problem syncing gma500 in native res using modesetting driver

Fixed the /usr/lib/initcpio/install/915resolution syntax, which appeared to be out-dated, updated the PKBUILD archive file and re-versioned 915resolution-static package to 0.5.3-10 with the syntax fix for both i686 and x86_64.

They're available at the same location -  http://bluestarlinux.org/index.php?acti … ds;cat=312

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