Re: [PATCH 1/3] mtd: atmel_nand: move the hsmc_clk from nfc node to nand node

[Boris Brezillon <boris.brezillon-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>]

Hi Josh,

On Tue, 10 Feb 2015 14:14:43 +0800
Josh Wu <josh.wu-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org> wrote:

> Also add a new sama5d3_nand compatiable string for sama5d3 nand.
> 
> For sama5d3, sama5d4 chip, the pmecc became part of HSMC, they need the
> HSMC clock enabled to work.
> The NFC is a sub feature for current nand driver, it can be disabled.
> But if HSMC clock is controlled by NFC, so disable NFC will also disable
> the HSMC clock. then, it will make the PMECC fail to work.
> 
> So the solution is move the HSMC clock out of NFC to nand node. When
> nand driver probed, it will check whether the chip has HSMC, if yes then
> it will require a HSMC clock.

Do you plan to use the NAND chip without the NFC (I mean, is there a
reason for not using the NFC to access the NAND ?) ?
If you don't, why don't you just wait for the NFC before probing the
NAND chip it is attached to, so that the hmsc clk is properly claimed.

I'm not convinced that moving a clk reference out of the controller
node can address the fact that the nand/nand-controller DT
representation is inappropriate (your embedding controller specific
information in your NAND chip definition).
I think we should reconsider this problem with a controller/chip
approach:
- which parts are representing the NAND controller: the PMECC engine,
  the NFC if available, ...
- which parts are representing the NAND chip: the EBI mem range, the
  R/B pin, the ALE/CLE information, ...

And of course, we should take the EBI/SMC rework into account ;-).

Best Regards,

Boris


-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
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