Hi,
I noticed that with touchscreen drivers that don't explicitly call a 
input_sync after input_register_device, suspend to ram is blocked if no 
event is sent, because the input_dev created is considered as not 
synchronized. The problem was seen with Atmel mxt driver. When any event 
is sent, the driver explicitly ask a sync, so the problem is solved.
The problem occurs only when the screen has never send any event before 
suspend to ram.
I solved it setting the sync element to true (when input dev is created, 
no element is pending).
Is there a better way to solve the problem ?
Thanks.
Thomas.