FDS - missing swap page

[Wojciech Jasko]

 Hi,

One of our devices is bricked due to the fds_init returning FDS_ERR_NO_PAGES. After flash analysis, I have discovered that all pages are marked as FDS_PAGE_DATA (no FDS_PAGE_SWAP). One of these pages is erased (just FDS_PAGE_TAG_MAGIC and FDS_PAGE_DATA header).

In our application, FDS is heavily used. During testing, we perform many power cycles. I do not have any clear reproduction path due to the fact that we found it just once (more than 200 devices online for a few months).

We are using SDK 14.2.0 with nRF52832 (custom board designs).

FDS flash dump can be found here: https://drive.google.com/drive/folders/1y_KOyIhVw9d-ZAAIc8SSa8k9vUOobDVz?usp=sharing

[Edvin]

Helllo,

I have been looking at this ticket a lot today, together with Terje, who is handling one of the other tickets. 

I have looked through a lot of documentation, done some testing by erasing pages, writing the magic word, but no tag and so on, but I have not found a way to reproduce ending up with all data pages and no swap page, which is what you are facing with this node.

So I have to ask, have you done any changes to the FDS module before programming these devices? Any fixes that were implemented beforehand that can affect the FDS behavior in any way?

That being said, it looks like somehow, the swap page has been tagged as a data page. In this page it is the first FDS page, at 0007D000. 

A suggested patch could be that if you end up with the NO_SWAP return from fds_init(), anything is better than just falling into APP_ERROR_CHECK(NO_SWAP);

As a workaround you can go through your FDS pages, and look for a page that contains the magic word and the data tag but no other data (all 0xFFFF). If you find one of these in the NO_SWAP state, it would be safe to assume that this page can be deleted. You can delete this page, then run fds_init() again. Alternatively, an NVIC_SystemReset(); 

If the FDS starts up with one empty page and the rest data pages, it will make the empty page to a SWAP page (I have tested this). 

What would be interesting is to see what happens if you erase this first page (from 0x0007D000) and reboot the application. Do you get any other errors at this point? Are the rest of the records valid, or do you get any information saying parts of the rest of the FDS are corrupted?