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7-inch Display Kit in Linux

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mkipper's picture
mkipper
Junior(0)
7-inch Display Kit in Linux

Hi, I'm working with a Zynq Mini-ITX dev board and the following display kit:
 
http://zedboard.org/product/7-inch-zed-touch-display-kit
 
The display kit provides a boot image with a bare-metal application that uses AXI VDMA to implement a frame buffer that draws to the screen. 
 
This works great, but I'm now interested in driving the display from Linux. Specifically, I'd like to do something with the display (full framebuffer support would be nice) from an existing 4.6 kernel I'm using. This is proving more difficult than I imagined.
 
I generated a device tree from the display kit reference design, and the only node that seems relevant is the AXI VDMA block itself. When I boot my kernel, the VDMA driver is loaded, and I can use 'devmem' to read its peripheral registers. This all seems to work, but I have no idea where to go next.
 
Are there any Linux drivers that work with this setup? All the Xilinx DRM/KMS drivers seem too complicated and designed for multi-stage video pipelines, and the Xilinx FB driver seems to be built around the TFT IP which I'm not using. Is there any simpler driver that works with this reference design?
 
Even if there is no driver, can I still test out the display in Linux somehow? Has anyone set up the VDMA to transfer a static image to the screen or anything like that?

zedhed's picture
zedhed
Moderator(22)
RE: 7-inch Display Kit in Linux

Hi mkipper,

We have some older examples of how to use the 7" kit with ZedBoard (and another using MicroZed + I/O Carrier) running Ubuntu Linux. These designs involved patching the DRM driver to force frame buffer output to match the 800x480 resolution of the display:

http://microzed.org/support/design/1668/13

Are you working with your local Avnet FAE on this project?

Regards,

-Kevin

mkipper's picture
mkipper
Junior(0)
Hey zedhed,

Hey zedhed,
I was in contact with an Avnet FAE, and he pointed me to an old Linux build (v2014.something) for the zedboard. I think it's the same one you're referencing. He also gave me a newer build (v2015.something) that was intended for a 10" display but had a possibility of working.
I didn't get anywhere with either of these.The FAE provided a Mini-ITX reference design (HDF file) for the ALI3 display , but I din't have any luck getting it to work with the older kernel build. I can load the bitstream without any issues, but the device tree wasn't really working out. I generated a device tree from the HDF file, but when loading the kernel, I lose my serial output and I can't really tell what's going on with the board. 
At this point, I feel like the best idea is to port the driver from the 2014 kernel to my newer kernel. I'll need to do this work at some point, so there isn't much benefit in getting the old build to work on the Mini-ITX board.