Re: [PATCH v3 4/7] tegra: fdt: Add NAND controller binding and definitions

[Scott Wood <scottwood@freescale.com>]

On 04/17/2012 03:18 PM, Simon Glass wrote:
> +Jim, who wrote the driver originally
> 
> Hi Scott,
> 
> On Tue, Apr 17, 2012 at 12:06 PM, Scott Wood <scottwood@freescale.com> wrote:
>>> + - nvidia,page-data-bytes : Number of bytes in the data area
>>> + - nvidia,page-spare-bytes : Number of bytes in spare area
>>> +       spare area = skipped-spare-bytes + data-ecc-bytes + tag-bytes
>>> +                     + tag-ecc-bytes
>>
>> Do you really need this stuff to be in the device tree?  You should be
>> able to determine this information from the ID table.
> 
> I suspect so - the driver originally had a lot of CONFIGs for this.
> Maybe someone who wants to take it further could do this as part of
> supporting ONFI?
> 
> I will see if Jim Lin can take another look.

You don't need ONFI to get the page/spare size out of the ID table.

The generic NAND code should already be doing this for you (fills in
mtd->writesize and mtd->oobsize).  If you need it during setup, we now
have CONFIG_SYS_NAND_SELF_INIT that allows splitting up
nand_scan_ident() from nand_scan_tail().

>>> +Nvidia NAND Controller
>>> +----------------------
>>> +
>>> +The device node for a NAND flash controller is as follows:
>>> +
>>> +Optional properties:
>>> +
>>> +nvidia,wp-gpios : GPIO of write-protect line, three cells in the format:
>>> +             phandle, parameter, flags
>>
>> Doesn't the number of cells depend on the GPIO controller binding?
> 
> Yes, but this is the binding Tegra uses.

Still, it doesn't belong in the NAND binding.  Maybe a future chip wants
to use this NAND binding but a different GPIO binding.  If nothing else,
people tend to copy-and-paste such descriptions.  We've still got people
adding bindings for Freescale devices saying interrupts are encoded as a
pair of cells, even though the interrupt controller now uses four cells
per interrupt.

-Scott