What is different between AF & AP? I understand AP = permission access as read/write/readonly/no access but what is AF?
You seem to talk about ARMv8-A. So check out:
DEN0024A - ARMv8 Programmer GuideDDI0478C_A - ARMv8 Reference Manualand
https://developer.arm.com/architectures/learn-the-architecture
Thanks again. I don't find good document that describe memory attributes. I also have question on Indx(MAIR_ELn) too. Do you any good reference doc?
Simply do only map memory which you want to use. Any other access generates a data abort.
AF is used for the OS. With AF == 0 you will get a data abort. Then the OS will know that the user process wants to use this memory, and takes action, like loading the data from external memory. Or doing a copy on write.
Thanks Bastian,
So for example, if I don't have a device(registers) at address 0x20000000 to 0x30000000 in our SOC. Should I set AF=0 or AF=1. I like to make sure we get data abort if someone try to access in any mode.
The AF is there to "record" an access. Not to allow or disallow an access. It is for the software (OS) to know if a certain memory area has been accessed and is kind of dirty.
I want to setup up some device memory to no access (no read/write). I want to make sure get data abort exception if it is access. Should I set both AP =0 and AF = 0?
Or AP=0 and AF=1 (access flag). why?
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