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No LiveVideo and /dev/fb0 when monitor unplugged from DP.

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Explorer
Posts: 177
Registered: ‎02-16-2014
Accepted Solution

No LiveVideo and /dev/fb0 when monitor unplugged from DP.

I got DiplayPort LiveVideo interface enabled, so I will get video data stream in PL for processing and output from PL to LVDS LCD panel. And everything works fine.

 

But if system boots without monitor - no /dev/fb0 appears until I plug monitor to DP and no video data coming from LiveVideo interface to PL (except clock which I get).

Plug - image on both monitor and LiveVideo, unplug monitor - no LiveVideo data.

 

How I can force/enable MaliGPU/FBDev to form image all the time - with or without monitor ?

 

 


Accepted Solutions
Explorer
Posts: 177
Registered: ‎02-16-2014

Re: No LiveVideo and /dev/fb0 when monitor unplugged from DP.

I got it to work.

 

So, solution is:

1. Switch to current (as of 26July2018) master branch of Xilinx Kernel from github repo. It contains a patch which allow enable DP without PHY's attached/configured.

2. Add flag "e" to kernel cmd, in my case: video=DP-1:1024x768@60e

 

View solution in original post


All Replies
Moderator
Posts: 356
Registered: ‎04-24-2017

Re: No LiveVideo and /dev/fb0 when monitor unplugged from DP.

Hi @fanat9,

 

Which release are you using? In 2018.1 DP driver supports hotplug

 

fbdev isn't initialized until the entire DRM pipeline is enabled.

 

If the lvds driver is implemented as a drm encoder driver, that will format the entire pipeline, and the fbdev will be initialized properly

if not, the drm core will see the pipeline as not complete, and fbdev emulation doesn't happen.

Thanks,
Sandeep
PetaLinux Yocto | Embedded SW Support

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Explorer
Posts: 177
Registered: ‎02-16-2014

Re: No LiveVideo and /dev/fb0 when monitor unplugged from DP.

[ Edited ]

Just switched to 2018.2

 

My design is just a PL converter/serializer of DP LiveVideo to LVDS based on XAPP1315 and I have to have it to work even if DP physically unplugged. I tried to pull DP_HPD_R line up and down, but it obviously failed to read EDID.

 

How I can force it always on? Its not possible to do thru devicetree?

Explorer
Posts: 177
Registered: ‎02-16-2014

Re: No LiveVideo and /dev/fb0 when monitor unplugged from DP.

[ Edited ]

So, I switched to new DP driver with this commit. which should allow init DP without PHY.

 

But it didn't help - if DP unplugged PLL shuts down, no clock/data on LiveVideo PS-to-PL, no FBDEV got created and etc.

 

Looking around I found next PL Display Driver description, but can't make sense of it. Can any body explain what it for and how to use it properly:

https://github.com/Xilinx/linux-xlnx/blob/master/Documentation/devicetree/bindings/display/xlnx/xlnx%2Cpl-disp.txt

 

Thanks in advance!

Explorer
Posts: 177
Registered: ‎02-16-2014

Re: No LiveVideo and /dev/fb0 when monitor unplugged from DP.

I got it to work.

 

So, solution is:

1. Switch to current (as of 26July2018) master branch of Xilinx Kernel from github repo. It contains a patch which allow enable DP without PHY's attached/configured.

2. Add flag "e" to kernel cmd, in my case: video=DP-1:1024x768@60e