SPI: DUAL/QUAD support

[js@sig21.net (Johannes Stezenbach)]

On Fri, Jul 05, 2013 at 06:45:01AM +0000, Gupta, Pekon wrote:
> 
> > Just as Johannes said. In my patch m25p80's changes is incomplete.
> > Because my inicial aim is to add the transfer width member to tell controller
> > the mode flash in. And I will attach new patch about m25p80 later.
> > Also you are right. There are really series of flashes do not support dual/quad
> > transfer. So I don't know whether there are any standard for serial-flash just
> > like the CFI for parallel-flash. Personally, to make a general standard and
> > a general code for serial-flash is necessary. So that we do not need to add
> > special function in m25p80.c.
> > 
> [Pekon]: Does below generic framework for spianand, suit your driver?
> http://lists.infradead.org/pipermail/linux-mtd/2013-July/047434.html
> 
> you should be able to extend the generic spinand API for all
> serial modes (SPI, Dual-SPI, Quad-SPI).
> As QSPI and Dual-SPI devices should implicitly support SPI (MISO/MOSI)
> So, you can do device probing using default SPI mode. And then based on
> DT inputs and device support upgrade to QSPI / Dual-SPI mode.
> And going forward extend it for direct memory-mapped device for XIP.

Not sure what you have in mind since NAND and NOR flash work very
differently, and SPI vs. memory-mapped is also very different.

But to add to the spinand review comments two things caught
my eye on quick glance over the code:

> +#define mu_spi_nand_driver_version "Beagle-MTD_01.00_Linux2.6.33_20100507"

seems like an unused leftover?  if the version number is
important then maybe better put it in commit message?

> +/bin/bash: 4: command not found

how did this get in there?


Johannes