[U-Boot] [PATCH 00/16] SF: Migrate to Linux SPI NOR framework

[Vignesh R]

On 14/12/18 3:43 PM, Jagan Teki wrote:
> On Wed, Dec 12, 2018 at 11:02 PM Vignesh R <vigneshr at ti.com> wrote:
>>
>> U-Boot SPI NOR support (sf layer) is quite outdated as it does not
>> support 4 byte addressing opcodes, SFDP table parsing and different types of
>> quad mode enable sequences. Many newer flashes no longer support BANK
>> registers used by sf layer to a access >16MB space.
>> Also, many SPI controllers have special MMIO interfaces which provide
>> accelerated read/write access but require knowledge of flash parameters
>> to make use of it. Recent spi-mem layer provides a way to support such
>> flashes but sf layer isn't using that.
>> This patch series syncs SPI NOR framework from Linux v4.19. It also adds
>> spi-mem support on top.
>> So, we gain 4byte addressing support and SFDP support. This makes
>> migrating to U-Boot MTD framework easier.
>>
>> Tested with few Spansion, micron and macronix flashes with TI's dra7xx,
>> k2g, am43xx EVMs. I dont have access to flashes from other vendors. So,
>> I would greatly appreciate testing on other platforms. Complete series
>> with dependencies here[1]
>>
>> For clean build on some platforms, depends on CONFIG_SPI_FLASH migration
>> to defconfigs [2]
>>
>> [1] https://github.com/r-vignesh/u-boot.git  branch: spi-nor-mig-patch-v1
>> [2] https://patchwork.ozlabs.org/patch/1007485/
>>
>> Patch 12-15 are compile tested.
> 
> Fist of all thanks for your time and work on this.
>
> Since most of the discussion on the individual patches seems similar,
> repeat and never ended. I'm trying to summarize my comments here.
> 1) You can sync or add new features by grabbing the code from Linux,
> but I don't recommend __UBOOT macro or any Linux specific stuff  in
> drivers/mtd/spi

I am fine either way.

> 2) For BAR support, lets place it as it is and support via spi-nor

Problem is, it not desirable to use BAR as default because its not
stateless and does not work with all flash parts. OTOH, it seems like 4
byte addressing (stateless dedicated opcode or with enter/exit 4 byte
mode) seems to be standard.
Also, Linux doesn't support BAR and haven't seen any request for BAR
support. Why support additional feature and burden of maintaining when
it may not be needed.

But if you insist, I just have to add BAR support back.

> 3) For dual flash, wait for Xilinx developers if they really want to support it?

Sorry, this feature was never supported properly *in mainline U-Boot*.
If support is needed in the future, we can accept patches on top of new
framework.

> 4) For non-dm code in spi-mem, no comments? (Tom is already commented,
> may be Simon can comment)
> 


-- 
Regards
Vignesh