Re: [PATCH v4 0/7] mtd: spi-nor: add a new framework for SPI NOR

On Friday 17 January 2014 12:36 PM, Jagan Teki wrote:

On Fri, Jan 17, 2014 at 7:32 AM, Huang Shijie[off-list ref]  wrote:

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On Thu, Jan 16, 2014 at 03:09:13PM +0530, Jagan Teki wrote:

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     After this patch, the layer is like:
                     MTD
           ------------------------
                    spi-nor
           ------------------------
                    m25p80
           ------------------------
                 spi bus driver
           ------------------------
                 SPI NOR chip

Just for looking on your new framework, is that above link correct.
I guess it should be MTD -- m25p80 -- spi-nor -- spi bus driver -- SPI NOR chip

I do not think so.
The spi-nor layer does not contact with the spi bus driver directly.

Yes - now I understand the flow from seeing the code.
With your new framework
1. not an exact spi-nor
     have one controller driver at drivers/spi/* will register to spi core.
     have m25p80.c will scan the flash details from
drivers/mtd/spi-nor/spi-nor.c and
     m25p80 will register the MTD core and for transfer calls m25p80
will calls spi core.
2. spi-nor style
     have  one controller driver at drivers/mtd/spi-nor/fsl-quadspi.c
will register MTD core
     and scan the flash details from drivers/mtd/spi-nor/spi-nor.c and
for transfer will calls
     through direct writel and readl with cmd+data fashion.

Correct me If my understanding was wrong.

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3) Can you explain your framework precisely take an example of like
spi_controller_A with spi_flash_A
and qspi_controller_B and qspi_flash_B - how will this new framework
operates.

The framework is just cloned from the m25p80.c, and extract the common code,
and provides more
hooks such as

@prepare/unpreare: used to do some work before or after the
              read/write/erase/lock/unlock.
     @read_xfer/write_xfer: We can use these two hooks to code all
              the following hooks if the driver tries to implement them
              by itself.
     @read_reg: used to read the registers, such as read status register,
              read configure register.
     @write_reg: used to write the registers, such as write enable,
              erase sector.
     @read_id: read out the ID info.
     @wait_till_ready: wait till the NOR becomes ready.
     @read: read out the data from the NOR.
     @write: write data to the NOR.
     @erase: erase a sector of the NOR.

My basic question is like I have a qspi spi controller in my SOC and I
designed two boards B1 and B2

okay.

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B1 with quad spi controller connected with non-flash as a slave and B2
with quad spi controller connected
with quad flash as a slave.

You can use the framework for B2. But for B1, you should not use the framework,
since this framework is just for the SPI-NOR. If you do not connected with
a NOR, i think it's better to code another driver for your controller.

Means we have two separate controller drivers for same controller one
with spi-nor and
another with spi is it?

Do you think this is a good idea, I understand you have a complete and
well guided new
spi-nor framework.

I dont think its a good idea to support a single controller with two
drivers for two different usecase.