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Random delays(upto 6 minutes) after closed the board for secure boot.

Question asked by Krishnan P on Dec 12, 2017
Latest reply on Dec 26, 2017 by Yuri Muhin

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Hi,

I have enabled Secure boot on i.MX6 Dual Lite custom board. I have enabled RNG_TRIM fuse and closed for secure boot. However, I see a strange behavior like occasionally the board is not able to boot up. TThis behavior observed in only on the boards which are closed for secure boot. The board has PMIC chip to control the supply of various voltage levels.

I have gone through the datasheet (Section 4.3.2.2 LDO_2P5 ( In i.MX6 Dual Lite datasheet)) that mention about the voltage requirement. Can anyone experienced similar problems? I am particularly interested in the voltage levels and clocks needed for secure boot and OCOTP controller.

Thanks in Advance,

Krishnan.

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Yuri Muhin

Dec 12, 2017 11:18 PM

Hello,

Please refer to section 3.3.2 (RNG Trim fuses) of app note AN4581,

Secure Boot on i.MX50, i.MX53, and i.MX 6 Series using HABv4, Rev. 1, 10/2015

https://www.nxp.com/docs/en/application-note/AN4581.pdf

Have a great day,
Yuri

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Krishnan P Dec 26, 2017 12:38 AM

Hello Yuri,

In the application note, it says deferring the instantiation of RNG is a recommended option. This can be achieved by adding below lines in CSF configuration.

[Unlock]

Engine = CAAM

Features = RNG

However the below line in the AN4581 made me little obscure.

"This does not affect HAB-signed or encrypted boot features. Until the device is closed, HAB does not instantiate the RNG at boot."

In my case, I have closed the device for secure boot. So will the deferring of RNG instantiation will reduce the boot time in my case?

Thanks,

Krishnan.

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Yuri Muhin

@ Krishnan P on Dec 26, 2017 1:54 AM

Hello,

Since Your device is closed, HAB does instantiate the RNG at boot and it

may take some time. For Linux it also will take some time, but we can hope

smaller.

Regards,

Yuri.

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3 Replies

Yuri Muhin Dec 12, 2017 11:18 PM
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Correct Answer
Hello,

Please refer to section 3.3.2 (RNG Trim fuses) of app note AN4581,
Secure Boot on i.MX50, i.MX53, and i.MX 6 Series using HABv4, Rev. 1, 10/2015

https://www.nxp.com/docs/en/application-note/AN4581.pdf

Have a great day,
Yuri

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Note: If this post answers your question, please click the Correct Answer button. Thank you!
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Krishnan P Dec 26, 2017 12:38 AM
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Hello Yuri,

In the application note, it says deferring the instantiation of RNG is a recommended option. This can be achieved by adding below lines in CSF configuration.
[Unlock]
Engine = CAAM
Features = RNG

However the below line in the AN4581 made me little obscure.
"This does not affect HAB-signed or encrypted boot features. Until the device is closed, HAB does not instantiate the RNG at boot."
In my case, I have closed the device for secure boot. So will the deferring of RNG instantiation will reduce the boot time in my case?

Thanks,
Krishnan.
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- Yuri Muhin @ Krishnan P on Dec 26, 2017 1:54 AM
  Mark Correct
  Correct Answer
  Hello,
  
  Since Your device is closed, HAB does instantiate the RNG at boot and it
  may take some time. For Linux it also will take some time, but we can hope
  smaller.
  
  Regards,
  Yuri.
  Like • Show 0 Likes0
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Random delays(upto 6 minutes) after closed the board for secure boot.

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