[U-Boot] [PATCH 1/3] nand: Add support for unlock.invert

[Joe Hershberger]

Hi Scott,

On Fri, Aug 17, 2012 at 3:53 PM, Scott Wood <scottwood at freescale.com> wrote:
> On 08/17/2012 03:31 PM, Joe Hershberger wrote:
>> NAND unlock command allows an invert bit to be set to unlock all but
>> the selected page range.
>>
>> Signed-off-by: Joe Hershberger <joe.hershberger at ni.com>
>> ---
>>  common/cmd_nand.c            | 13 ++++++++++---
>>  drivers/mtd/nand/nand_util.c |  9 ++++++---
>>  include/nand.h               |  4 ++--
>>  3 files changed, 18 insertions(+), 8 deletions(-)
>>
>> @@ -368,6 +369,8 @@ int nand_unlock(struct mtd_info *mtd, ulong start, ulong length)
>>
>>       /* submit ADDRESS of LAST page to unlock */
>>       page += (int)(length >> chip->page_shift);
>> +     if (invert)
>> +             page |= 1;
>>       chip->cmdfunc(mtd, NAND_CMD_UNLOCK2, -1, page & chip->pagemask);
>
> Why |= 1?  Is this some magic that the chip recognizes to implement
> "invert"?  Do all chips that support lock/unlock support this (none of
> the NAND chip manuals I have document lock/unlock at all as far as I
> could find)?  What if you want to unlock a non-inverted range that ends
> in a page with the low bit set?

According to the data sheet for the part I'm working with
(MT29F4G08ABADAH4) the unlock command has 2 commands... 0x23 and 0x24.
 The invert bit only exists for 0x24 (NAND_CMD_UNLOCK2).  The format
of the unlock commands specifys that block addresses are used,
therefore the LSb would never be set.  This bit-0 is defined to be
"invert area" for 0x24 and always LOW for 0x23.

-Joe