[U-Boot] [PATCH 1/2] mtd: vf610_nfc: mark page as dirty on block erase

[Scott Wood]

On Mon, 2015-03-30 at 13:02 -0400, Bill Pringlemeir wrote:
> On 24 Mar 2015, stefan at agner.ch wrote:
> 
> > The driver tries to re-use the page buffer by storing the page
> > number of the current page in the buffer. The page is only read
> > if the requested page number is not currently in the buffer. When
> > a block is erased, the page number is marked as invalid if the
> > erased page equals the one currently in the cache. However, since
> > a erase block consists of multiple pages, also other page numbers
> > could be affected.
> >
> > The commands to reproduce this issue (on a written page):
> >> nand dump 0x800
> >> nand erase 0x0 0x20000
> >> nand dump 0x800
> >
> > The second nand dump command returns the data from the buffer,
> > while in fact the page is erased (0xff).
> >
> > Avoid the hassle to calculate whether the page is affected or not,
> > but set the page buffer unconditionally to invalid instead.
> >
> > Signed-off-by: Stefan Agner <stefan at agner.ch>
> > ---
> > This are two bug fixes which would be nice if they would still
> > make it into 2015.04...
> >
> > drivers/mtd/nand/vf610_nfc.c | 3 +--
> > 1 file changed, 1 insertion(+), 2 deletions(-)
> >
> > diff --git a/drivers/mtd/nand/vf610_nfc.c
> > b/drivers/mtd/nand/vf610_nfc.c index 928d58b..9de971c 100644 ---
> > a/drivers/mtd/nand/vf610_nfc.c +++ b/drivers/mtd/nand/vf610_nfc.c @@
> > -369,8 +369,7 @@ static void vf610_nfc_command(struct mtd_info *mtd,
> > unsigned command, break;
> >
> > 	case NAND_CMD_ERASE1: - if (nfc->page == page) - nfc->page =
> > -1; + nfc->page = -1; vf610_nfc_send_commands(nfc->regs, command,
> > NAND_CMD_ERASE2, ERASE_CMD_CODE); vf610_nfc_addr_cycle(mtd, column,
> > page);
> 
> This change looks sensible.  It is also possible that because sub-pages
> were removed that we could just remove the caching all together.  It is
> possible that a higher layer may intentionally want to program and then
> do a read to verify.

It's more than possible -- Peter Tyser posted patches to do exactly that
for command-line NAND writes.

> I had seen that different FS seem to do 'write' and then immediately
> follow with a read.  If you believe the controller and the write status
> was ok, then I think it is fine to reuse the existing buffer and keep
> this caching.

If the upper layers want to cache then let them cache.

> I guess we want to stay the same as the mainline Linux you are
> submitting.

So fix Linux. :-)

-Scott