[PATCH 0/4] mtd: spi-nor: add a new framework for SPI NOR
Huang Shijie
b32955 at freescale.com
Fri Dec 6 03:18:08 EST 2013
On Thu, Dec 05, 2013 at 02:35:47PM +0000, Angus Clark wrote:
> Hi Brian,
>
> On 12/04/2013 06:44 PM, Brian Norris wrote:
> > On this topic, I have one more stick to throw on this fire; I have some
> > Broadcom hardware that consists of two pieces:
> >
> > (1) a true SPI controller, with single-line-I/O and
> > (2) a Serial Flash controller that can accelerate flash read, using
> > dual/quad I/O.
>
> We support one platform with properties similar to the hardware you describe,
> and such a hybrid configuration was in mind when I was thinking about the
> spi-nor framework. I am not sure how well this will come across over email, but
> I envisage something like this:
>
> spi-nor
> |
> v
> [spi-nor-xfer]
> |
> ------------------------------------------------
> | | |
> v v v
> spi-wrapper (<------) hybrid-driver serial-flash-driver
> | | |
> [SPI] | |
> | | |
> v | |
> generic-spi-driver | |
> | | |
> v v v
> [generic-SPI-Cntrl] [SPI-Flash-Read Cntrl] [SPI-Flash-Controller]
>
> The 'spi-nor' layer is responsible for Serial Flash domain knowledge, and how to
> generate 'spi-nor-xfer' messages. The 'spi-wrapper' would provide an interface
> to the generic SPI framework, flattening the 'spi-nor-xfer' message to standard
> SPI calls. The combination of 'spi-nor' and 'spi-wrapper' should achieve what
> we have today for the m25p80 driver. The 'serial-flash-driver' in the example
> provides an implementation for a dedicated Serial Flash Controller, making use
> of the spi-nor-xfer semantics where required. The 'hybrid-driver' could use the
> 'spi-wrapper' implementation for write and erase hooks, and optimised
> implementations for read hooks.
>
For the diagram above, I think we can regard the hybrid driver as a kind of
serial-flash-driver too.
thanks
Huang Shijie
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