on my customized imx6 android jb4.3 board, my kernel video cmdline has been set as below:
video=mxcfb0:dev=lcd,800*1280@60,if=RGB24,bpp=32 video=mxcfb1:dev=hdmi,1920x1080M@60,if=RGB24,bpp=32 video=mxcfb2:off fbmem=14M,28M vmalloc=512M
so after power on , the hdmi output is just the same as hdmi_no_rotate.jpg. in this picture, hdmi output is in portrait mode. it is not corrupt. but it have not cover the full hdmi screen.
so i unpluged the hdmi cable. and rotate the primary screen at 90 degrees to change it into landscape mode. after this, i plugged the hdmi cable again, and have found hdmi output corrupt when it is in landscape mode. please refer to hdmi_rotate.jpg below.
but at another video cmdline:
video=mxcfb0:dev=lcd,800*1280@60,if=RGB24,bpp=32 video=mxcfb1:dev=hdmi,1280x720M@60,if=RGB24,bpp=32 video=mxcfb2:off fbmem=14M,28M vmalloc=512M
in this video cmdline, hdmi output can not be corrupted when rotate the primay screen.
so i wonder why main screen hasn't been corrupt but sceond screen has been corrupt at hdmi 1080p,
and why main screen and second screen haven't been corrupt at hdmi 720P.
accoring to edid from my TV, both hdmi 720p and 1080p can be supported without any problem.
many thanks if some body can explain this reason.