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LCD interface flicker when HDMI/DVI enabled

Question asked by Danielle Loader on Dec 16, 2015
Latest reply on Jan 9, 2016 by Pingli Sui

Hi,

 

We noticed that when we try to enable the HDMI/DVI output in the kernel and the device tree, sometimes the LCD (RGB parallel) screen output is flickering. I've not been able to test it on many devices but it's 100% percent reproducible on those I've tested with this particular method:

 

We are using 1280x800 displays in the product so we configure these screens for this.

IPU1 DISP0 "sin1" mode for single LVDS display.

IPU0 DISP0 for the LCD.

IPU0 DISP1 for the DVI.

Then we've forced the DVI resolution to 1280x800 as it not in the "modes" list in sysfs by default with the following fbset command:

 

fbset -fb /dev/fb3 -g 1280 800 1280 800 16 -t 14063 40 40 10 3 80 10

 

Everything is working fine so far.

But when we try to set the resolution to 1280x720 on the DVI, we get a flickering screen on the LCD interface:

 

echo U:1280x720p-60 >/sys/class/graphics/fb3/mode

 

Then everything works well again if we set back to 1280x800:

 

echo U:1280x800p-60 >/sys/class/graphics/fb3/mode

 

More interestingly there is no flickering and everything works well when we set the resolution to 1080p first, then 720p:

 

echo U:1920x1080p-60 >/sys/class/graphics/fb3/mode

 

No flickering.

 

echo U:1280x720p-60 >/sys/class/graphics/fb3/mode

 

No flickering.

 

echo U:1280x800p-60 >/sys/class/graphics/fb3/mode

 

No flickering.

 

echo U:1280x720p-60 >/sys/class/graphics/fb3/mode

 

The LCD flickers again.

 

Have you ever met this problem? Is there a solution or workaround for this?

 

 

Is there a way to somehow routing the data provided by IDMAC (Image DMA Controller) for both DI (Display Interface) on same IPU? If yes, can you explain how?

 

Thank you

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