Hello Volker On Tue, Jan 30, 2018 at 9:38 PM, Volker Floeder wrote: > Hello Charles, > > we are working on an automotive project where we are in contact with the > German department of Micron. > > They did an evaluation of the project in their lab simulating automotive > environment, i.e. temperature. The result was a data retention time of > about 3 years, which simply isn't enough, so refreshing is needed in any > case. We have several r/w partitions and some r/o as well. > > So yes, a dedicated mounting option like the one you described would be > great. > > However, I think, we will need to implement a "read all nand pages" daemon > as well. > I am curious about what you mean by a "read all nand pages daemon". Would that just be something that ensures that all pages are occasionally read to prevent bit-rot going undetected? There is already something a bit like that for r/w partitions since Yaffs will, occasionally, rewrite the oldest block and thus force it to refresh. It sounds like what is needed here are: 1) A bit more active searching for bad pages. 2) Mount flags to allow fix-up for read-only. > > Regards, > Volker > > > ----- Ursprüngliche Mail ----- > Von: "Charles Manning" > An: "Volker Floeder" > CC: "Bean Huo (beanhuo)" , "yaffs" < > yaffs@stoneboat.aleph1.co.uk> > Gesendet: Montag, 29. Januar 2018 19:06:10 > Betreff: Re: [Yaffs] Read-Only mounted YAFFS2 - refreshing of NAND pages > > Hello Volker > > > Read-only mounting prevents any writes to Yaffs, including any refresh. > > It is true that NAND does have a read disturb issue were reading a page > can cause corruption of bits on OTHER pages in the same block. However this > typically takes many hundreds of thousands of read operations. > > It is also possible that there is leakage with time. > > The best way to assess the impact for your design is to discuss the read > disturb prevalence with your NAND manufacturer. > > Perhaps it would be good if Yaffs had a read-only mount mode that was read > only except for doing refresh. Does that sound like something useful? > > > Regards > > Charles > > > > > On Mon, Jan 29, 2018 at 10:48 PM, Volker Floeder < vf@floeder.com > wrote: > > > Ok, understood. Thanks! > > However, all pages that are used by yaffs should be read when the > file-system is mounted, correct? > > So at least after a boot, there should be a read-access across all valid > data. Or do I need some kind of "scrubbing" to be sure? > > > ----- Ursprüngliche Mail ----- > Von: "Bean Huo (beanhuo)" < beanhuo@micron.com > > An: vf@floeder.com > CC: yaffs@stoneboat.aleph1.co.uk > Gesendet: Montag, 29. Januar 2018 10:04:22 > Betreff: RE: [Yaffs] Read-Only mounted YAFFS2 - refreshing of NAND pages > > > > >Hi, > > > >I am wondering if the page-refresh works on a read-only mounted filesystem > >as well. However, if it would not, then some flash blocks might get > >uncorrectable read-errors after some period of time, so I'd expect that to > >work - but on the other hand, it might be a bad idea to mount read-only at > >all ... > > > >Does anybody know? Thanks! > > > >- Volker > > > > > > According to my understanding, if there is read action on this read-only > mounted > Partition, page-refresh will work. Even for the read-write mounted > filesystem, if no read action, > page-refresh doesn't work. > mtd layer will report bitflips to file system layer, rather than file > system itself. > > > > > > > > >------------------------------ > > > >Subject: Digest Footer > > > >_______________________________________________ > >yaffs mailing list > > yaffs@stoneboat.aleph1.co.uk > > http://stoneboat.aleph1.co.uk/cgi-bin/mailman/listinfo/yaffs > > > > > >------------------------------ > > > >End of yaffs Digest, Vol 150, Issue 2 > >************************************* > > _______________________________________________ > yaffs mailing list > yaffs@stoneboat.aleph1.co.uk > http://stoneboat.aleph1.co.uk/cgi-bin/mailman/listinfo/yaffs > > > > >