AM57X GLSDK: Get LCD encoders ID error

Hi experts, 

I've build the GLSDK and run the API drmextended on AM5728.

processors.wiki.ti.com/.../DRA7xx_GLSDK_Software_Developers_Guide

error Segmentation fault is occurred while getting the lcd encoder id, I found the problem is caused by dev->lcd_con is NULL. 

Could you give some hints?

Thank you !

Regards,