[U-Boot] [PATCH] nand: reinstate lazy bad block scanning

[Scott Wood]

On Wed, 2014-11-05 at 12:40 +0900, Masahiro Yamada wrote:
> Hi Scott, Rostislav,
> 
> On Mon, 3 Nov 2014 15:42:29 -0600
> Scott Wood <scottwood at freescale.com> wrote:
> 
> > On Wed, 2014-10-22 at 13:40 +0200, Rostislav Lisovy wrote:
> > > Commit ff94bc40af3481d47546595ba73c136de6af6929
> > > ("mtd, ubi, ubifs: resync with Linux-3.14")
> > > accidentally reverted part of the commit
> > > 13f0fd94e3cae6f8a0d9fba5d367e311edc8ebde
> > > ("NAND: Scan bad blocks lazily.").
> > > 
> > > Reinstate the change as by commit
> > > fb49454b1b6c7c6e238ac3c0b1e302e73eb1a1ea
> > > ("nand: reinstate lazy bad block scanning")
> > > 
> > > Signed-off-by: Rostislav Lisovy <lisovy at merica.cz>
> > > ---
> > >  drivers/mtd/nand/nand_base.c | 10 +++++++---
> > >  1 file changed, 7 insertions(+), 3 deletions(-)
> > 
> > Thanks for catching this.  
> > 
> > Heiko, this is the sort of thing I was concerned about with the "resync
> > from scratch" approach.
> > 
> 
> I do not believe resync is a bad idea,
> of course we should be very careful not to break existing features.

I'm not saying don't sync -- I'm saying do it by generating a diff based
on the last sync (which is what all the previous NAND updates did),
rather than throwing out the U-Boot code and replacing it with Linux
files, and then fixing any problems encountered (which may be a subset
of the problems existing).

> I recommend to surround this code with "#ifdef __UBOOT__  ... #endif"
> as we have done for the other parts.

I recommend not making such a mess, for reasons I've described
previously.

> BTW, we attempt to probe NAND devices during the boot sequence
> just for displaying the device size, right?
> 
> NAND:  **** MiB
> 
> 
> If so, can we postpone the whole of nand_scan
> until we use it?  I am not sure about this, though.

Possibly.  IIRC someone once posted a patch trying to do this, but it
was missing an initialization check on some paths where NAND could be
accessed, and the patchset never got respun.

-Scott