SAMA5D27-WLSOM1 + Linux4SAM: resume from Backup Self-Refresh mode

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mikehaben
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Joined: Mon Jul 22, 2019 4:20 pm

SAMA5D27-WLSOM1 + Linux4SAM: resume from Backup Self-Refresh mode

Wed Oct 16, 2019 11:41 am

A question particularly for the Microchip engineers on this forum - is Linux4SAM "resume from mem-sleep" proven on the WLSOM1 (SAMA5D27 with LPDDR2) using Backup Self-Refresh mode?
I see that Claudiu Beznea made a commit to AT91Bootstrap 9 days ago "Add BSR support for LPDDR2 memories with SAMA5D2", but there hasn't been a commit to Linux4SAM in this area for many months. In my current debug setup (a custom PCB using the ATSAMA5D27C-LD2G LPDDR2 SIP), it appears that the pointers stored in SECURAM on the SAMA5 are being maintained during mem-sleep, but data in LPDDR2 are being lost or corrupted, which suggests to me that Linux4SAM is not correctly configuring the MPDDRC (Multiport DDR-SDRAM Controller) registers before going to sleep. I'd like to know whether this feature has been proved to work on (say) a WLSOM1-EK board, or is a Microchip work-in-progress, before spending time looking at possible hardware (power-supply-related) causes on our board.

Thank you,
Mike H.
ASH Wireless
manuels
Posts: 3
Joined: Tue Oct 01, 2019 5:37 pm

Re: SAMA5D27-WLSOM1 + Linux4SAM: resume from Backup Self-Refresh mode

Fri Aug 21, 2020 5:02 pm

I am trying to test this mode in a SAMA5D27-SOM1-EK1 and I have the same feeling. The pointers are saved in the SECURAM but the content in "pm->canary" address is not what at91bootstrap is expecting. And what is worse, bootstrap gets stuck in an infinite loop trying to boot from mem rather than falling back to a cool boot. The only way to get out of this loop is disconnecting the battery backed supply to clear the SECURAM or waiting for the supercap to be discharged.

I am testing this with the Yocto image available in sam4linux: linux4sam-poky-sama5d27_som1_ek-headless-2020.04.img.bz2 and the minimum required chages in bootstrap and linux cmd to enable BSR. I am either missig something from PmFaq: https://www.linux4sam.org/bin/view/Linux4SAM/PmFaq or something is not properly done in the kernel when changing to BSR mode.
nferre
Site Admin
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Re: SAMA5D27-WLSOM1 + Linux4SAM: resume from Backup Self-Refresh mode

Wed Sep 02, 2020 2:49 pm

Hi,

Backup with Self-Refresh (BSR) mode only works for SAMA5D2 boards which preserve the VDDIODDR power rail.
It's not the case for SAMA5D27 SOM1 EK nor SAMA5D2 PTC boards, so you can't use BSR mode on these boards. On SOM1, it's due to the SOM, not only the base board design.

BSR mode was tested working with Linux4SAM 2020.04 on SAMA5D27 WLSOM1 EK, SAMA5D2 Xplained and SAMA5D2 ICP boards.

Hope that it clarifies. Best regards,
Nicolas
manuels
Posts: 3
Joined: Tue Oct 01, 2019 5:37 pm

Re: SAMA5D27-WLSOM1 + Linux4SAM: resume from Backup Self-Refresh mode

Thu Sep 17, 2020 6:01 pm

Thank you very much for the clarification Nicolas.
That clearly explains why the content in the DDR is not mantained :oops:

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