[U-Boot] [PATCH] NAND: Updating the NAND README

[Paulraj, Sandeep]

> 
> On Tue, Dec 01, 2009 at 01:06:07PM -0500, s-paulraj at ti.com wrote:
> > +MTD NAND 64 bit support:
> > +========================
> > +
> > +The MTD NAND infrastructure in U-Boot(until release 2009.11) used only
> > +32 bit values to represent device size. As a result of which if we use
> > +a NAND device of size 4 GB and above, the MTD NAND driver will not
> detect
> > +such a NAND device due to overflow.
> > +NANDs comes in various flavours. There are some NANDs which are
> > +internally 2 devices and have 2 chipselects. If the SOC specific
> > +NAND driver is designed to treat each NAND device as a separate device
> > +then we will still be able to detect the entire 4GB of a NAND device.
> > +Each chipselect being responsible for 2 GB address space.
> > +But if at the U-Boot level we want to have access to the entire 4GB
> address
> > +space then the only way to achieve this is to update the MTD and NAND
> drivers
> > +with 64 bit values.
> > +The Linux kernel was updated with 64 bit values sometime in December
> '08.
> > +The core NAND driver is now similar to the core NAND driver in the
> kernel.
> > +We appropriately update the MTD layer in U-Boot.
> > +In the process of syncing up with the kernel we have also updated the
> > +NAND driver with other enhancements that made its way to the NAND
> driver.
> > +
> > +After these features were added, testing was performed on a wide
> > +range of NAND devices with page size of 64 KiB, 128KiB, 256KiB and 512
> > +KiB. Also 2 separate 4GB NAND devices(one from SAMSUNG and one from
> MICRON)
> > +were successfully tested. U-Boot was able to correctly detect the
> device
> > +and read bad blocks.
> 
> Hmm, not sure we need to describe here what was, rather than what is.

Let me know what parts you want removed. I just decided to put as much info as possible with a little history as well.
> 
> > +What is lacking?
> > +================
> > +
> > +We need to add 64 bit support in cmd_nand.c and env_nand.c as well.
> > +Without this certain diagnostcis
> 
> typo
> 
> > will fail. For example,
> > +issuing a "nand bad" command results in the same bad blocks being
> > +found infinite times. This happens if we use a 4 GB NAND device.
> > +This will not occur if NANDs of smalles than 4 GB are used.
> 
> s/of smalles than/smaller than/
I'll fix the typos

> 
> > +At this point of time it appears as if the entire common folder
> > +needs to be updated with 64 bit values.
> 
> Yeah...  If you want to put a concise note about this here, I'll add it,
> though an actual bug tracking system would be nice. :-)

Again let me know what sections are not required.
> 
> -Scott

I'll send an updated patch after your reply.

Sandeep