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Thread: Overscan on the radeon driver

  1. #1
    Join Date
    Nov 2009
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    19

    Question Overscan on the radeon driver

    I'm using the lastest radeon stack from xorg-edgers which is working well w/KMS. The problem is that I'm pushing a rear projection DLP @ 1080p and getting the usual ~5% overscan. With the catalyst blob the default modelines come up perfectly scanned to the viewable edges of the screen. So figured I'd start by feeding the modelines that fglrx reports to the radeon driver. The modelines are identical for all resolutions with the exception of the h/vsync settings:

    FGLRX
    "1920x1080" 148.50 1920 2008 2052 2200 1080 1084 1089 1125 -hsync -vsync

    Radeon OSS
    "1920x1080" 148.50 1920 2008 2052 2200 1080 1084 1089 1125 +hsync +vsync

    These are as detected by EDID. So it's likely that the fglrx is doing some additional scaling to produce the correctly scanned output. The detected DPI and sceen demensions are identical on both drivers.

    Using xrandr to add the fglrx modeline to the radeon driver works but switching to "1080_test" does not. The screen flashes and Xrandr reports that it has switched but the output of xvidtune -show indicates that the settings in use are from the originally detected modeline. I should note that I have not disabled EDID yet, but I've never needed to do so to use custom modelines with other drivers/cards.

    Any advice on fixing overscan on the oss driver? Any idea as to what ATI may be doing to default to correct viewable area for my screen with identical modeline demensions?

  2. #2
    Join Date
    Nov 2009
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    19

    Default

    I should add that I've just started and have only tried with xrandr so far. Xorg.conf is moved out of the way. The radeon driver is detecting correctly but most use cases nowadays would be LCD based w/o overscan.

    The eventual goal is to run MythTV at 720p for <720 content and 1080p for larger. Since it will only run 720 while showing video the over scan isn't a big problem. I'm also looking for a way to pass custom modes so the console is usable. But I'm not finding much info about how to do this with the KMS/DDX changes that are in place. Mode switches are quick though.

  3. #3
    Join Date
    Oct 2007
    Location
    Toronto-ish
    Posts
    7,434

    Default

    Are you connected via HDMI ? If so, then check to see if your display is set to overscan -- it's still a pretty common factory default.

    The fglrx driver does a deliberate underscan by default on HDMI-attached HD displays in order to show the whole screen even if the display has overscan enabled.

  4. #4
    Join Date
    Nov 2009
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    19

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    Correct, I'm using HDMI, I'm keeping the faith that Alex's audio patches will see day light. There is no way to disable overscan on the TV. There are 3 levels of overscan with the lowest being about 3%. It still cuts off the taskbars and hides the edges of the console.

    I guess the thread should be "Underscanning on the Radeon Driver", maybe I can play with xrandr scaling features, but I'd like the card to drive it rather than relying on additional transforms.
    Last edited by rjwaldren; 12-08-2009 at 03:13 PM.

  5. #5
    Join Date
    Nov 2009
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    19

    Default

    Scaling kind of works but introduces other problems... It still bases the screen off of 0,0 which is off screen and xrandr --pos has no effect. SO I can bring in the left and bottom but the right and top remain out of the viewable area. There are also slow redraws and a disappearing mouse pointer when scaling small amounts.

    Does radeon OSS allow custom mode lines like the Nvidia "res in a res" function. The normal tools like CVT/GFT can't even generate the mode-lines that the OSS driver is using and doesn't like the fglrx lines.

    EDIT ^^^ yes it does, I have it working with a 1856x1044 modeline with just enough overscan to hide the edges. But now if I VT switch VT7 stays black upon return.
    Last edited by rjwaldren; 12-08-2009 at 08:07 PM.

  6. #6
    Join Date
    Oct 2009
    Location
    United States
    Posts
    9

    Default Overscan on the radeon driver

    Cheers - will give badsectors a go; when you say a long time any idea how long? Just copying back over the data Id lost.

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