[U-Boot] [PATCH v2] spi/kirkwood: add weak functions board_spi_bus_claim/release

[Valentin Longchamp <valentin.longchamp@keymile.com>]

Hi Prafulla,

On 03/28/2012 09:48 AM, Prafulla Wadaskar wrote:
>> On 03/26/2012 11:58 AM, Valentin Longchamp wrote:
>>> Some kirkwood based boards may need to implement such function due
>> to
>>> some HW designs.
>>
>> I see no feedback from your side on this patch. I think you should go
>> through
>> the marvell tree:
>>
>> - the spi_claim/release_bus function are already implemented in the
>> SPI subsystem
>> - this patch touches only a kirkwood driver
>> - there is no spi u-boot tree from what I see
>>
>> Please keep me up to date about the status of this patch
> 
> Hi Valentin,
> I have gone through this patch and related implementation in your other patch_series.
> http://lists.denx.de/pipermail/u-boot/2012-March/120716.html
> 
> Basically spi_claim_bus and spi_release_bus are not supported in current Kirkwood spi driver.
> These are needed if someone wish to share the same interface pins with some other peripheral (that is your use case)

Correct, this is exactly our use case: we have the NAND Flash Controller and the
SPI controller that share the same pins.

> 
> But this is not board specific whereas, it should be feature enhancement for Kirkwood spi driver.

This is correct for the mpp part of spi_claim_bus. If you look at the actual
implementation that we do in our board specific function, there is an additional
step that is needed by our board design.

> 
> You should add this support very similar to multiple CS pin selection support added to the Kirkwood driver, no external (board specific triggers needed)
> 
> Here are my suggestions:
> 1. Configure these mpps in your board specific files as NF pins.
> 2. Populate below logic for claim/release bus feature in Kirkwood spi driver.
> 2.a. When spi_claim_bus will be called, backup current mpps status and reconfigure these mpps for SPI in Kirkwood_spi driver.
> 2.b. When spi_release_bus will be called, reconfigure with backed up mfg as SPI pins
> 2.c. Add check for to avoid multiple claim for same bus
> 

OK, I agree with this, but I would add:
2.d. call weak attribute functions boad_spi_claim/release_bus at the end of
spi_claim/release_bus functions

-- 
Valentin Longchamp
Embedded Software Engineer
Hardware and Chip Integration
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