The iMX31 Windows CE 5.0 display driver, starting with version 0.4.0 (lpd_imx31_ipu_imx31_50_0_4_0) includes power management functions. This means that when you go into suspend, the backlight and LCD will be disabled to save power.
One thing that also happens, is that Windows CE will automatically use a system timer to put the display into a 'idle' mode. Any interrupt will wake the display back up.
This may catch a few people off guard and there is a way to disable it.
By default, it is set to 5 minutes (300 seconds). You can change this by setting the following registry item, for example to '0' so that it never does this.
; Overwrite the Power Management Suspend Time-outs otherwise the
; Sample Power Manager will shutdown the display during it's
; 'SystemIdle' sytem power mode
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Power\Timeouts]
; "ACUserIdle"=dword:3c; in seconds
"ACSystemIdle"=dword:0; in seconds, CE default value is '12c'
; "ACSuspend"=dword:0; in seconds
; "BattUserIdle"=dword:3c; in seconds
; "BattSystemIdle"=dword:b4; in seconds
; "BattSuspend"=dword:12c; in seconds