[PATCH for 3.7] mtd: nand: fix Samsung SLC NAND identification regression

[PATCH for 3.7] mtd: nand: fix Samsung SLC NAND identification regression

[Brian Norris]

A combination of the following two commits caused a regression in 3.7-rc1
when identifying some Samsung NAND, so that some previously working NAND
were no longer detected properly:

    commit e3b88bd604283ef83ae6e8f53622d5b1ffe9d43a
    mtd: nand: add generic READ ID length calculation functions

    commit e2d3a35ee427aaba99b6c68a56609ce276c51270
    mtd: nand: detect Samsung K9GBG08U0A, K9GAG08U0F ID

Particularly, a regression was seen on Samsung K9F2G08U0B, with the
following full 8-byte READ ID string:

    ec da 10 95 44 00 ec da

The basic problem is that Samsung manufactures both SLC and MLC NAND
that use a non-standard decoding table for deriving information from
their IDs. I have heuristically determined that all the chips that use
the new table have ID strings which wrap around after the 6th byte.
Unfortunately, I overlooked the fact that some older Samsung SLC (which
use a different decoding table) have "5 byte ID strings" which also wrap
around after the 6th byte.

This patch re-introduces a distinction between these old and new Samsung
NAND by checking that the 6th byte is non-zero, allowing both old and
new Samsung NAND to be detected properly.

Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Tested-by: Brian Norris <computersforpeace@gmail.com>
Reported-by: Marek Vasut <marex@denx.de>
Tested-by: Marek Vasut <marex@denx.de>
---
David,

Marek and I just discovered this issue during the merge window. Please merge
this fix in the 3.7-rc cycle. Thanks.

 drivers/mtd/nand/nand_base.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index ec6841d..d5ece6e 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -2983,13 +2983,14 @@ static void nand_decode_ext_id(struct mtd_info *mtd, struct nand_chip *chip,
 	/*
 	 * Field definitions are in the following datasheets:
 	 * Old style (4,5 byte ID): Samsung K9GAG08U0M (p.32)
-	 * New style   (6 byte ID): Samsung K9GAG08U0F (p.44)
+	 * New Samsung (6 byte ID): Samsung K9GAG08U0F (p.44)
 	 * Hynix MLC   (6 byte ID): Hynix H27UBG8T2B (p.22)
 	 *
-	 * Check for ID length, cell type, and Hynix/Samsung ID to decide what
-	 * to do.
+	 * Check for ID length, non-zero 6th byte, cell type, and Hynix/Samsung
+	 * ID to decide what to do.
 	 */
-	if (id_len == 6 && id_data[0] == NAND_MFR_SAMSUNG) {
+	if (id_len == 6 && id_data[0] == NAND_MFR_SAMSUNG &&
+			id_data[5] != 0x00) {
 		/* Calc pagesize */
 		mtd->writesize = 2048 << (extid & 0x03);
 		extid >>= 2;
-- 
1.7.11.3

Re: [PATCH for 3.7] mtd: nand: fix Samsung SLC NAND identification regression

[David Woodhouse]

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On Tue, 2012-10-09 at 23:26 -0700, Brian Norris wrote:
> I have heuristically determined that all the chips that use
> the new table have ID strings which wrap around after the 6th byte.

I'd be happier if we had confirmation of that from Samsung...

-- 
dwmw2

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Re: [PATCH for 3.7] mtd: nand: fix Samsung SLC NAND identification regression

[Brian Norris]

On Tue, Oct 9, 2012 at 11:31 PM, David Woodhouse <dwmw2@infradead.org> wrote:
> On Tue, 2012-10-09 at 23:26 -0700, Brian Norris wrote:
>> I have heuristically determined that all the chips that use
>> the new table have ID strings which wrap around after the 6th byte.
>
> I'd be happier if we had confirmation of that from Samsung...

I can see if that's possible, but I think it's unlikely. They don't
even bother following standards (ONFI). Is this an obstacle to
merging?

Brian

Re: [PATCH for 3.7] mtd: nand: fix Samsung SLC NAND identification regression

[David Woodhouse]

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On Tue, 2012-10-09 at 23:39 -0700, Brian Norris wrote:
> I can see if that's possible, but I think it's unlikely. They don't
> even bother following standards (ONFI). Is this an obstacle to
> merging?

No. I already pushed it.


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Re: [PATCH for 3.7] mtd: nand: fix Samsung SLC NAND identification regression

[Marek Vasut]

Dear David Woodhouse,

> On Tue, 2012-10-09 at 23:39 -0700, Brian Norris wrote:
> > I can see if that's possible, but I think it's unlikely. They don't
> > even bother following standards (ONFI). Is this an obstacle to
> > merging?
> 
> No. I already pushed it.

Thanks guys!

Best regards,
Marek Vasut

Re: [PATCH for 3.7] mtd: nand: fix Samsung SLC NAND identification regression

[Brian Norris]

Hi David,

On Wed, Oct 10, 2012 at 12:48 AM, David Woodhouse <dwmw2@infradead.org> wrote:
> On Tue, 2012-10-09 at 23:39 -0700, Brian Norris wrote:
>> I can see if that's possible, but I think it's unlikely. They don't
>> even bother following standards (ONFI). Is this an obstacle to
>> merging?
>
> No. I already pushed it.

This is a "bump" for a 3.7-rc pull request. This regression has been
noticed by others.

Thanks,
Brian

Re: [PATCH for 3.7] mtd: nand: fix Samsung SLC NAND identification regression

[Marek Vasut]

Dear Brian Norris,

> Hi David,
> 
> On Wed, Oct 10, 2012 at 12:48 AM, David Woodhouse <dwmw2@infradead.org> wrote:
> > On Tue, 2012-10-09 at 23:39 -0700, Brian Norris wrote:
> >> I can see if that's possible, but I think it's unlikely. They don't
> >> even bother following standards (ONFI). Is this an obstacle to
> >> merging?
> > 
> > No. I already pushed it.
> 
> This is a "bump" for a 3.7-rc pull request. This regression has been
> noticed by others.

[whine] my nand doesn't work ;-)

Thanks for keeping eye on this, Brian.

Best regards,
Marek Vasut