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

[sourav <sourav.poddar@ti.com>]

On Friday 17 January 2014 12:36 PM, Jagan Teki wrote:
> On Fri, Jan 17, 2014 at 7:32 AM, Huang Shijie<b32955@freescale.com>  wrote:
>> On Thu, Jan 16, 2014 at 03:09:13PM +0530, Jagan Teki wrote:
>>>>>>      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.
>>>>> 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.
>>
>>> 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.