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Visitor
Visitor
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Registered: ‎08-11-2019

is return stack implemented in Zynq 7000 SOC

Hi,

I am working on some research project based on ZC706 board that contain Zynq-7000 soc. i need to know that is Cortex-A9 Cpu in Zync-7000 implemented Return Stack Buffer (Return Stack Buffer is an program flow speculation technique like branch prediction) or no. In Zync-7000 Technical reference manual i saw some registers that indicate that Return Stack was implemented or no.

RSB-1.png

as you can see in ETMCCER register bit 23 indicate return stack implementation detail and it's reset value is 0.

now i want to know that this means that Return Stack did not implemented in this SOC? Right?

and second question, how can i read this register during execuation of program?

 

Thanks for your attention

 

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Xilinx Employee
Xilinx Employee
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Registered: ‎10-04-2016

Re: is return stack implemented in Zynq 7000 SOC

Hi @alireza11045 ,

The return stack is implemented in the Zynq-7000. 

Can you tell me where you got that copy of the ETMCCR register? That does not at all match what is printed in v1.12.2 of UG585.

https://www.xilinx.com/support/documentation/user_guides/ug585-Zynq-7000-TRM.pdf#page=962etmccr.JPG

Regards,

Deanna

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Visitor
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Registered: ‎08-11-2019

Re: is return stack implemented in Zynq 7000 SOC

Thanks for your response.

i told that "ETMCCER" register, not "ETMCCR" register. in document that you indicated in page "988" describe "ETMCCER" register.

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Xilinx Employee
Xilinx Employee
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Registered: ‎10-04-2016

Re: is return stack implemented in Zynq 7000 SOC

Hi @alireza11045 ,

That extra "E" in "ETMCCER" makes a big difference.

Looking through the PTM documentation from ARM, it appears the Return Stack that the register refers to is located in the PTM. It is not the same Return Stack that is in the A9 core.

This is the document I am referring to:

http://infocenter.arm.com/help/topic/com.arm.doc.ddi0401c/DDI0401C_coresight_ptm_a9_r1p0_trm.pdf

Regards,

Deanna

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