Hi,
I'm currently trying to change the frequency of a PXA270 processor, the system I'm working on is a Linux 2.6.24, and I would like to write a code that allows an user to change the frequency, to do so I need to write in a register of coprocessor 14. According to ARM documentation i need to use MRC/MCR instructions, I tried but I got an error : "Illegal instruction".
It seems that I should use Software Interrupt in order to switch from user mode to supervisor mode and then use MRC/MCR instructions, but I don't know how the OS will handle that interrupt. I'm not even sure that what I want to do is possible, but if it is, does someone have any idea of the code I should write to switch to supervisor mode and use MRC or MCR instruction?
Thanks,