[U-Boot] [PATCH v10 00/27] dm: Generic MTD Subsystem, with SPI-NOR interface

[Prabhakar Kushwaha]

Dear Jagan,

> -----Original Message-----
> From: U-Boot [mailto:u-boot-bounces at lists.denx.de] On Behalf Of Jagan
> Teki
> Sent: Thursday, December 28, 2017 11:42 AM
> To: u-boot at lists.denx.de
> Cc: Tom Rini <trini at konsulko.com>
> Subject: [U-Boot] [PATCH v10 00/27] dm: Generic MTD Subsystem, with SPI-
> NOR interface
> 
> Compared to previous series’s [1], [2], [3] and [4] this patch set redefined
> most of the implementation suitable to fit into existing driver-model.
> 
> MTD is generic subsystem for underlying flash devices like nand, parallel nor,
> spinor, dataflash etc. So to drive this theory with driver model(with an
> example of block layer) mtd is common device interaction for most of
> memory technology flashes like nand, parallel nor, spinor, dataflash etc,
> these are treated as interface types wrt u-boot driver model.
> 
> Once the respective interface driver bind happen, the uclass driver will pass
> an 'interface type' to mtd layer to create device for it, for example once
> spinor ULASS_SPI_NOR driver bind happen, the uclass driver of spinor will
> pass MTD_IF_TYPE_SPI_NOR interface type to create mtd device for spinor
> devices.
> 
> SPI-NOR:
> =======
> Some of the SPI device drivers at drivers/spi not a real spi controllers, Unlike
> normal/generic SPI controllers they operates only with SPI-NOR flash
> devices. these were technically termed as SPI-NOR controllers, Ex:
> drivers/spi/fsl_qspi.c
> 
> The problem with these were resides at drivers/spi is entire SPI layer
> becomes SPI-NOR flash oriented which is absolutely a wrong indication
> where SPI layer getting effected more with flash operations - So this SPI-NOR
> core will resolve this issue by separating all SPI-NOR flash operations from spi
> layer and creats a generic layer called SPI-NOR core which can be used to
> interact SPI-NOR to SPI driver interface layer and the SPI-NOR controller
> driver.
> 
> =======================================
>              cmd/spinor.c
> =======================================
>              mtd-uclass.c
> =======================================
>            spi-nor-uclass.c
> =======================================
>               spi-nor.c
> =======================================
> m25p80.c                zynq_qspinor.c
> =======================================
> spi-uclass.c
> =======================================
> zynq_qspi.c
> =======================================
>         #####SPI NOR chip######
> =======================================
> 

As per this patch-set, fsl_qspi is looks to be getting proposed in driver/mtd/spi-nor/ folder.

fsl_qspi is supporting both flash and fpga.  We are not sure about its location. 

There is an on-going effort for similar type of requirement in Linux by Boris Brezillon . It is dealing with controllers supporting NORs, NANDs, SRAMs etc. 
http://patchwork.ozlabs.org/project/linux-mtd/list/?series=27088

Borris has also ported fsl_qspi in driver/spi to use this new framework. It is still not completely tested.  
https://github.com/bbrezillon/linux/commit/43cc45764b975bfbb191de3f6a37e073da1a2706


Will you also follow similar approach as being done in http://patchwork.ozlabs.org/project/linux-mtd/list/?series=27088 for longer term?

For Now, We are planning to update fsl_qspi driver to support dynamic LUT. Similar patch is in progress in Linux http://patchwork.ozlabs.org/project/linux-mtd/list/?series=26084
Now we are confused, should be port fsl_qspi in driver/mtd/spi-nor and then update driver
Or
We update driver/spi/fsl_qspi for dynamic LUTs. We may need to modify existing framework to get all required info for dynamic LUT.  

Also we want some change in framework like support of
 -  4 byte address and SFDP :  http://patchwork.ozlabs.org/project/uboot/list/?series=19621&state=*
 -  SMPT : in discussion in Linux http://patchwork.ozlabs.org/patch/869718/
 Which code base should we use?   u-boot-spi.git branch mtd-spinor-working  or u-boot.git master branch

--pk