[U-Boot] [PATCH 1/6] arm: socfpga: cyclone5-socdk: Enabling mtd partitioning layout

[Marek Vasut]

On Monday, December 14, 2015 at 01:11:27 AM, Chin Liang See wrote:
> On Sun, 2015-12-13 at 16:42 +0100, Marek Vasut wrote:
> > On Sunday, December 13, 2015 at 02:03:02 PM, Chin Liang See wrote:
> > > On Sun, 2015-12-13 at 04:14 +0100, Marek Vasut wrote:
> > > > On Sunday, December 13, 2015 at 01:49:06 AM, Chin Liang See
> > > > 
> > > > wrote:
> > > > > On Sun, 2015-12-13 at 01:01 +0100, Marek Vasut wrote:
> > > > > > On Sunday, December 13, 2015 at 12:59:48 AM, Chin Liang See
> > > > > > 
> > > > > > wrote:
> > > > > > > On Sat, 2015-12-12 at 16:36 +0100, Marek Vasut wrote:
> > > > > > > > On Saturday, December 12, 2015 at 07:30:46 AM, Chin Liang
> > > > > > > > See
> > > > > > > 
> > > > > > > > wrote:
> > > > > > > [...]
> > > > > > > 
> > > > > > > > > > Can you share the final layout before you roll out
> > > > > > > > > > patches ?
> > > > > > > > > 
> > > > > > > > > Sure, plan to do so but need to away from desk just
> > > > > > > > > now.
> > > > > > > > > 
> > > > > > > > > Here is the old layout
> > > > > > > > > 256k(spl)
> > > > > > > > > 64k(env)
> > > > > > > > > 64k(dtb)
> > > > > > > > > 256k(boot)
> > > > > > > > > 16m(kernel)
> > > > > > > > > 16m(rootfs)
> > > > > > > > > 
> > > > > > > > > The new one would like this
> > > > > > > > > 256k(spl)
> > > > > > > > 
> > > > > > > > I'd say you should just call this u-boot, see above for
> > > > > > > > the
> > > > > > > > rationale.
> > > > > > > > 
> > > > > > > > > 256k(env)
> > > > > > > > > 15872k(boot)
> > > > > > > > > 16m(rootfs)
> > > > > > > > > 
> > > > > > > > > The boot partition can be used as ubi part or raw
> > > > > > > > > partition.
> > > > > > > > > It contains the linux dtb, u-boot and linux images.
> > > > > > > > 
> > > > > > > > Is that an UBIFS partition ? If so, why don't you just
> > > > > > > > use
> > > > > > > > two
> > > > > > > > UBI
> > > > > > > > volumes ?
> > > > > > > 
> > > > > > > For backward compatibility, it can be raw if user want to
> > > > > > > stick
> > > > > > > with
> > > > > > > old way.
> > > > > > 
> > > > > > If you're breaking the partitioning layout anyway, you don't
> > > > > > have
> > > > > > to
> > > > > > care about the "old way", right ?
> > > > > 
> > > > > Actually this partition can be used as raw partition if user
> > > > > don't
> > > > > want
> > > > > to store zimage and dtb as raw binary.
> > > > 
> > > > You should never store raw zImage/dtb in a flash on a production
> > > > system.
> > > > This is real bad and can result in a corruption in the future
> > > > when
> > > > the
> > > > system is in the field for a long time. I'd suggest to just use
> > > > two
> > > > UBI
> > > > volumes, one for fitImage and the other for rootfs.
> > > 
> > > Yup, we are trying to move the raw away by having UBI enabled. I
> > > presume when you refer 2 UBI volumes, I presume its still single
> > > UBI
> > > partition?
> > 
> > Yeah, one UBI partition with two UBI volumes -- boot and root.
> 
> Ok I grasp you correctly. In this case, I would suggest to opt for 2
> partitions instead of 2 volumes. User can just use sf erase rootfs
> instead of checking for volume offset. I suspect the ubi part will take
> longer time if we are having one partition only. I shall send out the
> new revision if this works for you :)

Oh, I see what you're concerned about. On the other hand, you are not supposed 
to erase UBI partition, since that'd nuke the UBI erase counters and UBI would
loose track of how many times each block was erased, which helps with wear 
leveling.

If you're adamant about two UBI partitions , you can try the trick where you can
create overlapping mtd partitions, that way you'd have both options available.
(it is actually a legal construction, you can check the kernel MTD docs).