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Accessing CP14 from user mode
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Accessing CP14 from user mode
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Ackbar Ackbar
over 7 years ago
Note: This was originally posted on 9th July 2009 at http://forums.arm.com
Hello,
I'm currently trying to change the frequency of a PXA270 processor, the system I'm working on is a Linux OS, 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".
So I think I need to switch to supervisor mode, it seems that I could do it using SWI but even after reading some documentation I don't know how I should implement this.
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,
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kuan po huang
over 7 years ago
Note: This was originally posted on 5th August 2009 at
http://forums.arm.com
hi,
if you can modify kernel source, here is an option:
add system calls to read/write coprocessors
there are many tutorials about adding system calls in embedded linux kernel
embedded Linux kernel takes short time to build
googling "add system call" should help
thanks
Kuan-Po Huang
High Performance Computing Lab.
CSIE, National Chung Cheng University, Taiwan
[url="
http://hpc.cs.ccu.edu.tw/
"]
http://hpc.cs.ccu.edu.tw/[/url]
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kuan po huang
over 7 years ago
Note: This was originally posted on 5th August 2009 at
http://forums.arm.com
hi,
if you can modify kernel source, here is an option:
add system calls to read/write coprocessors
there are many tutorials about adding system calls in embedded linux kernel
embedded Linux kernel takes short time to build
googling "add system call" should help
thanks
Kuan-Po Huang
High Performance Computing Lab.
CSIE, National Chung Cheng University, Taiwan
[url="
http://hpc.cs.ccu.edu.tw/
"]
http://hpc.cs.ccu.edu.tw/[/url]
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