linux runs on STMP36XX , problems remains

hi, guys
   we have ported linux on STMP36XX. Untill now we implement a serial
console on Application UART, MTD driver for nand, TD018 LCD driver.
Using initrd or jiffs2 on nandflash we could boot linux to prompt on
serial console. we also implement a simple framebuffer driver to
display on LCD. With miniGUI, a sample bomb program could show on the
LCD. for absence of input device on LCD, We can't trigger the display
updating operation.
    So we want the console also be sent to LCD, we add the framebuffer
console to the kernel,but system
suspend in function register_framebuffer, by tracing in, we found  that
os sleep in  function acquire_console_sem(printk.c).
    We ported the kernel  following the EP7312 ,to us  it is relatively
easy to imitate.
    We dont known who is holding the console semaphore, the serial
console?
    have any reading material about console semaphore recommanded?