[PATCH] mtd: nand: auto-detection of NAND bus-width from ONFI param or nand_id[]

[Gupta, Pekon]

Hi Ezequiel,


> From: Ezequiel Garcia [mailto:ezequiel.garcia at free-electrons.com]
> Thanks for taking care of this! :-)
> 
Yes, I was waiting for -rc1 to be TI-GPMC driver which still gets configured
from DT independently. However that’s a separate discussion already
going in your earlier thread.


> > On Mon, Nov 25, 2013 at 06:02:08PM +0530, Pekon Gupta wrote:
[...]
> > +
> > +	/* re-configure driver is bus-width was incorrectly configured */
> > +	if (busw != (chip->options & NAND_BUSWIDTH_16)) {
> > +		pr_warn("reconfiguring NAND bus width to %d instead %d
> bit\n",
> > +			   busw ? 16 : 8,
> > +			   (chip->options & NAND_BUSWIDTH_16) ? 16 : 8);
> > +		chip->options = (chip->options & ~NAND_BUSWIDTH_16) |
> busw;
> 
> Looking at this makes me wonder why are we *re* configuring, instead of
> just configuring. I mean, why do we keep the NAND_BUSWIDTH_16 setting?
> 
> What use case might need the user to set it, before hand?
> 
Nothing.. I just said reconfiguring, bcoz some driver already configure
'chip->options & NAND_BUSWIDTH_16' pre-hand before calling
nand_scan_ident(). So, I wanted to convey that this patch should not
affect any of their functionality. And no change is should be required.

Need this to get tested with -ve testing on different boards.. 
(like setting in-correct DT binding nand-bus-width and driver should still
be able to detect and probe ONFI params) Then only it proves that this
patch is actually auto-detecting bus-width under all cases for all controllers.


with regards, pekon