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Changing HDMI resolution via command issue

Question asked by victor Wang on May 14, 2018

Hi All,

I'm developing  Android 6 image on i.MX6 sabreSD DL.

Here I facing the problem.

Command line settings and kernel driver settings are all 1920X1080 HDMI.

Output show perfectly then.

 

When I try to change the resolution from FULL HD to 1280x720 by below command.

echo "S:1280x720p-60" > /sys/class/graphics/fb0/mode

Then output will not show as expect, It shows like below picture.

 

And if I try to change the command line from

bootargs console=ttymxc1,115200 init=/init video=mxcfb0:dev=hdmi,1920x1080M@60,if=RGB24,bpp=32  video=mxcfb1:off video=mxcfb2:off video=mxcfb3:off  vmalloc=256M androidboot.console=ttymxc1 consoleblank=0 androidboot.hardware=FA30H_HW100 cma=384M androidboot.selinux=disabled androidboot.dm_verity=disabled

to

bootargs console=ttymxc1,115200 init=/init video=mxcfb0:dev=hdmi,1280x720M@60,if=RGB24,bpp=32  video=mxcfb1:off video=mxcfb2:off video=mxcfb3:off  vmalloc=256M androidboot.console=ttymxc1 consoleblank=0 androidboot.hardware=FA30H_HW100 cma=384M androidboot.selinux=disabled androidboot.dm_verity=disabled

 

The output will show like below picture.

According to the red circle in the picture, I can't understand why there is black blank there.

 

In conclusion, two question for total.

  1. Why the output shows strange while I change the resolution by command?
  2. Why it will shows black blank if I change the resolution settings in command line?

 

Thanks in Advanced!

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