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generic timer difference armv8a and cortex-a53

ARMv8-A Architecture Reference Manual written

An EL1 physical timer.

An EL2 physical timer.

An EL3 physical timer.

A virtual timer.

but, Cortea-A53 Technical Reference Manual written

A Non-secure EL1 physical timer.

A Secure EL1 physical timer.

A Non-secure EL2 physical timer.

A virtual timer.

"An EL1 physical timer" is "A Non-secure EL1 physical timer."?

"An EL3 physical timer" is "A Secure EL1 physical timer" ?

or just like armv7-a,

"A Non-secure EL1 physical timer"/"A Secure EL1 physical timer" is banked.

and It is An EL1 physical timer?

  • "An EL1 physical timer" is "A Non-secure EL1 physical timer."?

    "An EL3 physical timer" is "A Secure EL1 physical timer" ?

    Yes, and it's unfortunate that the two docs don't use consistent names.  I'll report this to our docs group.

    NOTE: What the Architecture Reference Manual describes as "EL3 physical timer" can be configured to be accessible from S.EL1. Controlled by SCR_EL3.ST.  I suspect that is where the confusion is naming came from.

  • Thanks so much.

    I understand it.

    It is too confusing.

  • Hi,

    I have recently joined ARM and also I am new to ARM architecture.
    Please could you kindly explain the difference between a physical timer & virtual timer (also between physical & virtual counter). I guess EL stands for exception level. Please could you point me to right sources from where I can get detailed info on the timers.

    Best regards