[PATCH v2] mtd/spi-nor: Add SPI memory controllers for Aspeed SoCs

[Rob Herring]

On Wed, Nov 09, 2016 at 11:42:29AM +0100, Cédric Le Goater wrote:
> This driver adds mtd support for spi-nor attached to either or both of
> the Firmware Memory Controller or the SPI Flash Controller (AST2400
> only).
> 
> The SMC controllers on the Aspeed AST2500 SoC are very similar to the
> ones found on the AST2400. The differences are on the number of
> supported flash modules and their default mappings in the SoC address
> space.
> 
> The Aspeed AST2500 has one SPI controller for the BMC firmware and two
> for the host firmware. All controllers have now the same set of
> registers compatible with the AST2400 FMC controller and the legacy
> 'SMC' controller is fully gone.
> 
> Each controller has a memory range on which it maps its flash module
> slaves. Each slave is assigned a memory window for its mapping that
> can be changed at bootime with the Segment Address Register.
> 
> Each SPI flash slave can then be accessed in two modes: Command and
> User. When in User mode, accesses to the memory segment of the slaves
> are translated in SPI transfers. When in Command mode, the HW
> generates the SPI commands automatically and the memory segment is
> accessed as if doing a MMIO.
> 
> Currently, only the User mode is supported. Command mode needs a
> little more work to check that the memory window on the AHB bus fits
> the module size.
> 
> Based on previous work from Milton D. Miller II <miltonm at us.ibm.com>
> 
> Signed-off-by: Cédric Le Goater <clg at kaod.org>
> ---
>  Tested on:
> 
>  * OpenPOWER Palmetto (AST2400) with
>  	FMC controller : n25q256a
> 	SPI controller : mx25l25635e and n25q512ax3
> 
>  * Evaluation board (AST2500) with
>  	FMC controller : w25q256 
> 	SPI controller : w25q256
> 
>  * OpenPOWER Witherspoon (AST2500) with
>  	FMC controller : mx25l25635e * 2
> 	SPI controller : mx66l1g45g
> 
>  Changes since v2:
> 
>  - added a set4b ops to handle difference in the controllers
>  - simplified the IO routines
>  - prepared for fast read using dummy cycles
> 
>  Work in progress:
> 
>  - read optimization using higher SPI clock frequencies
>  - command mode to direct reads from AHB
>  - DMA support
> 
>  .../devicetree/bindings/mtd/aspeed-smc.txt         |  72 ++

Acked-by: Rob Herring <robh at kernel.org>

>  drivers/mtd/spi-nor/Kconfig                        |  12 +
>  drivers/mtd/spi-nor/Makefile                       |   1 +
>  drivers/mtd/spi-nor/aspeed-smc.c                   | 783 +++++++++++++++++++++
>  4 files changed, 868 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/mtd/aspeed-smc.txt
>  create mode 100644 drivers/mtd/spi-nor/aspeed-smc.c