On Fri, 29 Oct 2021 at 13:13, Pintu Agarwal <pintu.ping@xxxxxxxxx> wrote: > > Hi All, > > On Mon, 30 Aug 2021 at 21:28, Pintu Agarwal <pintu.ping@xxxxxxxxx> wrote: > > > > On Sun, 22 Aug 2021 at 19:51, Ezequiel Garcia > > <ezequiel@xxxxxxxxxxxxxxxxxxxx> wrote: > > > > > In other words, IMO it's best to expose the NAND through UBI > > > for both read-only and read-write access, using a single UBI device, > > > and then creating UBI volumes as needed. This will allow UBI > > > to spread wear leveling across the whole device, which is expected > > > to increase the flash lifetime. > > > > > > For instance, just as some silly example, you could have something like this: > > > > > > | RootFS SquashFS | > > > | UBI block | UBIFS User R-W area > > > ------------------------------------------------------------------------ > > > Kernel A | Kernel B | RootFS A | RootFS B | User > > > ------------------------------------------------------------------------ > > > UBIX > > > ------------------------------------------------------------------------ > > > /dev/mtdX > > > > > > This setup allows safe kernel and rootfs upgrading. The RootFS is read-only > > > via SquashFS and there's a read-write user area. UBI is supporting all > > > the volumes, handling bad blocks and wear leveling. > > > > > Dear Ezequiel, > > Thank you so much for your reply. > > > > This is exactly what we are also doing :) > > In our system we have a mix of raw and ubi partitions. > > The ubi partitioning is done almost exactly the same way. > > Only for the rootfs (squashfs) I see we were using /mtd/block<id> to > > mount the rootfs. > > Now, I understood we should change it to use /dev/ubiblock<id> > > This might have several benefits, but one most important could be, > > using ubiblock can handle bad-blocks/wear-leveling automatically, > > whereas mtdblocks access the flash directly ? > > I found some references for these.. > > So, this seems good for my proposal. > > > > Another thing that is still open for us is: > > How do we calculate the exact image size from a raw mtd partition ? > > For example, support for one of the raw nand partitions, the size is > > defined as 15MB but we flash the actual image of size only 2.5MB. > > So, in the runtime how to determine the image size as ~2.5MB (at least > > roughly) ? > > Is it still possible ? > > > > I am happy to inform you that using "ubiblock" for squashfs mounting > seems very helpful for us. > We have seen almost the double performance boost when using ubiblock > for rootfs as well as other read-only volume mounting. > > However, we have found few issues while defining the read only volume as STATIC. > With static volume we see that OTA update is failing during "fsync". > That is ota_fsync is failing from here: > https://gerrit.pixelexperience.org/plugins/gitiles/bootable_recovery/+/ff6df890a2a01bf3bf56d3f430b17a5ef69055cf%5E%21/otafault/ota_io.cpp > int status = fsync(fd); > if (status == -1 && errno == EIO) > * > { have_eio_error = true; } > * > return status; > } > > Is this the known issue with static volume? > I don't know exactly how you are updating your volume, the right way is using UBI_IOCVOLUP. See http://www.linux-mtd.infradead.org/doc/ubi.html#L_volupdate If you google around I'm sure you'll find some articles about this, but I'm not sure if they'll go into details and subtleties. There are probably a few different ways to do firmware upgrade when you are on top of static volumes (and you want to be on top of static volumes if it's read-only, because AFAIK they give you an extra data-integrity guarantee). One way, would be to have two static volumes A/B. The system uses normally the A volume, and then you doUBI_IOCVOLUP (or ubiupdatevol) to update the B volume. After the update is succesful you run the atomic volume rename and flip A->B, B->A. (If you don't have enough space to hold two A/B volumes.... ... you'll have to find some other solution, I have no idea about that.) Hope it helps, Eze
