mtd layer: support of hybrid flash(W25M161AW) having both NOR and NAND flash
boris.brezillon at free-electrons.com
Thu Jan 4 09:47:22 PST 2018
On Thu, 4 Jan 2018 14:08:42 +0000
Prabhakar Kushwaha <prabhakar.kushwaha at nxp.com> wrote:
> Hi All,
> Winbond has come up with special flash i.e. W25M161AW. It consist of Serial NOR(Die #0) and Serial NAND(Die #1) flash.
> Means both NOR, NAND flashes are placed in W25M161AW controlled by single chip-select.
> "Software Die Select (C2h)" command is being used to switch die or flash.
Why are they so mean to us?! :-)
> It looks to be quite unique chip and wondering if any kind framework or work in progress available to handle it.
> I know that SPI-NAND framework discussions is still in progress.
Well, nothing impossible to handle, we just need to declare 2 MTD
devices (one NAND and one NOR). This being said, it looks like we'll
need this spi-flash abstraction we have been talking about with Marek
and Cyrille to properly support these use cases: flash devices will be
exposed through different sub-layers (spi-nor or spi-nand), but we need
a common way to detect those spi-flash chips. I looked at a few SPI
NAND and SPI NOR chips, and from what I've seen so far they were quite
different (the opcodes and CMD+ADDR+DATA sequences were quite
different) so I thought we were safe to start with a completely
unconnected SPI NAND framework and merge some bits in a spi-flash layer
afterwards, but this chip proves me wrong :-/.
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