mtd: nand: lock unlock function

[Huang Shijie]

On Wed, Nov 05, 2014 at 04:00:29PM -0600, Zhi Li wrote:
> On Wed, Nov 5, 2014 at 2:57 PM, Brian Norris
> <computersforpeace at gmail.com> wrote:
> > +
> >
> > On Wed, Nov 05, 2014 at 02:31:34PM -0600, Zhi Li wrote:
> >> Does any know the reason why there are nand_lock and nand_unlock
> >> function in nand_base.c, but
> >>
> >>         mtd->_lock = NULL;
> >>         mtd->_unlock = NULL;
> >>
> >> Not set to nand_lock and nand_unlock?
> >
> > Possible answers:
> >
> >  * Lack of testing
> >
> >  * The LOCK/UNLOCK opcodes are not supported by all vendors
> >
> >  * Even the vendors that support them don't do so consistently (not sure
> >    about this one; I know Micron supports this in some cases)
> >
> >  * The opcodes aren't even documented (again, I'm not even sure about
> >    this one; but many Micron datasheets I see don't mention LOCK/UNLOCK.
> >    I recall that other similar lock/protection implementations are
> >    secret to some extent, and are intentionally omitted from the
> >    datasheets)
> 
> Yes, we recently met a problem with micron flash. Need send unlock command.
> The datasheet I get from micron
> MT29F8G08ABACA, MT29F8G16ABACA, MT29F8G08ABBCA,
> MT29F8G16ABBCA, MT29F16G08ADACA, MT29F16G16ADACA,
> MT29F16G08ADBCA , MT29F16G16ADBCA
> 
> support it.
> But not sure if it is public document.
> 
could you please describe what is the problem?

thanks
Huang Shijie