How to access SNVS_LPCR[TOP] by software on i.MX6

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How to access SNVS_LPCR[TOP] by software on i.MX6

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vsiles
Senior Contributor I

Following my investigation on https://community.nxp.com/message/995605 , is it possible to assert SNVS_LPCR[TOP] by software to trigger a software power off ? I'm trying to write to it (after setting SNVS_LPCR[DP_EN]) but I never see the bit set to 1 and the poweroff never happens.

Are there special requirements to do so ? I'm at Supervisor EL1 Secure Mode (TZ) in Non-Secure Mode (SNVS, SSM_ST = 0xb)

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marius_grigoras
NXP Employee
NXP Employee

Hi Vincent,

Is this a customer board I think, right?

In this case, please make sure you have connected PMIC_ON_REQ to PMIC_PWRON. Without these connected, that patch will not work. 

By default, as far I know, PMIC_ON_REQ should connect directly to SNVS_PMIC_ON_REQ.

Best regards,

Marius

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igorpadykov
NXP Employee
NXP Employee

Hi Vincent

one can look at example on

Q&A: How is mx6 PMIC_ON_REQ under SW control? 

Best regards
igor
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vsiles
Senior Contributor I

Dear igorpadykov

From what I gather from mariusviorelgrigoras-b32331‌'s answer and the link you posted, is that I should be able to poweroff the board by writing 0x60 to SNVS_LPCR (bit TOP and DP_EN).

What can I do to check it actually works: I tried to write them both (at the same time, or DP_EN, and then TOP) and:

- I never see the bit TOP set whereas the doc says it should be set to 1 during the shutdown sequence

- My boards continues to run code without powering down

I didn't messed much with the IOMUX pads (didn't change much after u-boot's configuration) so maybe I need to change some things here so the PMIC_ON_REQ signal is correctly routed ? My goal is to power down the board, and I don't see to be able to correctly write to SNVS_LPCR. Do I need to configure something before doing this write ?

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marius_grigoras
NXP Employee
NXP Employee

Hi Vincent,

Is this a customer board I think, right?

In this case, please make sure you have connected PMIC_ON_REQ to PMIC_PWRON. Without these connected, that patch will not work. 

By default, as far I know, PMIC_ON_REQ should connect directly to SNVS_PMIC_ON_REQ.

Best regards,

Marius

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vsiles
Senior Contributor I

I contacted Boundary Devices, and they don't have a PMIC on the sabre lite, which explains why it doesn't work. Thank you for all your support !

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vsiles
Senior Contributor I

It is a sabre lite by Boundary Devices, but I also have a Sabre SD I could test on (I'm working on the Sabre Lite at the moment). How can I check this connection ? Is it done by software or should I check the hw specs ?

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vsiles
Senior Contributor I

Hi !

I already got a first look at this document a couple days ago but it didn't make much sense to me at the time. I'll try to understand it better before asking more information. Thank you for your time !

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