[U-Boot] [PATCH] atmel nand patch CE don't care NAND

[Scott Wood]

On Tue, 8 Feb 2011 21:52:10 +0100
Michael Trimarchi <trimarchi at gandalf.sssup.it> wrote:

> Hi,
> 
> On 02/08/2011 09:29 PM, Scott Wood wrote:
> > On Wed, Feb 02, 2011 at 04:11:29PM +0100, Michael Trimarchi wrote:
> >> Hi,
> >>
> >> this patch fix the support for CE don't care nand
> >>
> >> Michael Trimarchi
> >
> > Please read http://www.denx.de/wiki/U-Boot/Patches and follow the
> > format therein -- don't use attachments.
> >
> The thunderbird config was wrong. I will use mutt next time
> >> commit 0cb23ef858407a7a9de6e353e08394637c518c89
> >> Author: Michael Trimarchi <michael at evidence.eu.com>
> >> Date:   Wed Feb 2 14:24:21 2011 +0100
> >>
> >>     Fix the CE for the NAND don't care
> >>     
> >>     Signed-off-by: Michael Trimarchi <michael at evidence.eu.com>
> >
> > The changelog needs to be more descriptive.  What is "NAND don't care"?
> > What is broken?
> >
> From atmel documentation:
> 
> "CE connection depends on the NAND Flash. For standard NAND Flash devices, it must be connected to any free PIO line.
> For “CE don’t care” NAND Flash devices, it can be connected to either NCS3/NANDCS or to any free PIO line."

So the absence of CONFIG_SYS_NAND_ENABLE_PIN means it's connected to
NCS3/NANDCS (which is not quite the same as having a "CE don't care" NAND
chip, since you still have the option of using a PIO line).

I'd just say something like this in the changelog (assuming my assumption
about how this works is correct), and wouldn't bother with an in-code
comment:

atmel_nand: don't require CONFIG_SYS_NAND_ENABLE_PIN

If NCE is hooked up to NCS3, we don't need to (and can't) explicitly set
the state of the NCE pin.  Instead, the controller asserts it
automatically as part of a command/data access.  Only "CE don't
care"-type NAND chips can be used in this manner.

-Scott