Re: [RFC PATCH 0/5] RFC for Zynq QSPI

[Boris Brezillon <boris.brezillon@bootlin.com>]

On Mon, 17 Sep 2018 17:05:22 +0200
Boris Brezillon <boris.brezillon@bootlin.com> wrote:

> Hi Naga,
> 
> On Mon, 17 Sep 2018 16:08:26 +0530
> naga suresh kumar <nagasureshkumarrelli@gmail.com> wrote:
> 
> > Hi all,
> > 
> > Can i write the Zynq QSPI driver under the new spi/mem framework?  
> 
> Yes, you should.
> 
> > As i said, it needs tweaking the mtd->size and spi read/write addresses.  
> 
> Can you elaborate a bit on why you think this is needed? Did you look
> at [1]? Maybe it will prevent us from exposing the flash size at the
> spi-mem level.
> 
> > Can somebody share your thoughts on this(Adding Zynq QSPI Dual parallel and
> > stacked)?  
> 
> I always have a hard time with this naming. I guess stacked is when you
> have 2 chips sharing the same I/O bus, and parallel is when you have 2
> chips with one taking all of the I/O and the other taking the other

			^half of the I/O bus and the other one

> half. Is that correct?
> 
> If it is, then stacked mode should be easy to support (it's just a
> matter of patching the spi layer to allow passing several CS lines to a
> single device (in case of DT parsing, it means reg = <0 1> implies CS 0
> and 1 are assigned to the same device. For the parallel, I don't have a
> solution yet.
> 
> Anyway, I'd suggest that you start with something simple (a spi-mem
> driver supporting ->exec_op() in Single/Dual/Quad mode), and build on
> top of that for the advanced features you're mentioning here.
> 
> Regards,
> 
> Boris
> 
> [1]http://lists.infradead.org/pipermail/linux-mtd/2018-June/081460.html