Greetings,
I’m working with a board we’ve designed running an Octavo OSD3358 C-Sip which contains an AM335x processor. The board is running a BuildRoot generated version of Linux. We are pushing video out to a VGA port and are getting acceptable results with standard VESA modes, in this case 1280x1024@60Hz. However, for our purposes we’d like to be able to hit higher refresh rates than 60Hz. Due to the screen resolution and the pixel clock of the processor, 126MHz, this cannot be done without using reduced blanking (75Hz refresh would require a pixel clock of 135MHz). I’ve used various timing calculators to generate reduced blanking mode parameters (that are correct according to the calculators and the internet at large), when I try to use these reduced blanking modes either from xorg.conf OR directly from xrandr I get errors like:
xrandr: Configure crtc 0 failed
Research informs me that in newer versions of Xorg7 (which is part of our Linux image) the xorg.conf file needs the “ReducedBlanking” option set to true, which I have added to the xorg configuration file. Yet, the errors persist.
I looked at xrandr’s source code and as far as I can tell the above error is emitted when xrandr queries another part of graphics system about the presence of a particular mode (and fails to find it). I’m not sure if it’s checking against the EDID list or what, but regardless, it fails with reduced blanking modes.
My questions are the following:
- The tilcdc driver supports reduced blanking, correct? I’ve seen indications that it does in some of the device tree overlay code for the beaglebone black 7” LCD cloak.
- Should I be looking at the code that generates the framebuffer? The ‘fb0’ that appears in the /dev directory.
- Does something need to change in the device tree?
Any insight into this issue would be enormously helpful.
Best regards,
Ian King
