[U-Boot] Porting Linux's MTD/NAND changes into U-Boot

[Heiko Schocher]

Hello Tom, Boris,

Am 25.04.2016 um 19:36 schrieb Tom Rini:
> On Mon, Apr 25, 2016 at 04:43:14PM +0200, Boris Brezillon wrote:
>
>> Hi Scott,
>>
>> I've recently contributed a lot of MTD/NAND related patches (and intend
>> to continue doing so). Some of them are transversal changes touching the
>> MTD and NAND framework internals, which implies patching all NAND
>> drivers along with the core changes.
>>
>> All those changes are required to properly handle modern NANDs (MLC/TLC
>> NANDs), and I need them to add proper NAND support to the sunxi
>> platform (and more particularly to the C.H.I.P from NextThing Co.).
>>
>> So my question is, how should I port those changes to U-Boot? I see
>> that your doing "synchronization commits", but in my case this mean
>> including a bunch of driver specific changes into this "sync commit".
>>
>> I think it's also worth mentioning that I plan to heavily rework the
>> Linux NAND framework to improve NAND performances on modern NAND
>> controllers and clarify the NAND chip / NAND controller concepts, and
>> other people are also working on merging the BBT code of the NAND and
>> OneNAND framework. Which unfortunately means that we're not done porting
>> invasive changes to U-Boot :-/.
>>
>> Any advice is welcome.
>
> I suppose my first suggestion would be to sync the kernel back into
> U-Boot more frequently.  With our bi-monthly release cycle it shouldn't
> be too hard to pick a window to grab the current kernel release and
> bring it over.  I think the more stuff we let build up prior to syncing
> the harder it will be.

Yes, the same applies for UBI/UBIFS. I have no real strategy yet for
this. I think also, we need when doing such a sync a better testframe-
work, which tests on ideally a lot of boards the new versions ...

Without this, it is very difficult not to break existing boards with
such a sync ... especially MTD is tricky, I think, because a lot of
boards use it ...

I know I am nerving with my tbot [1], but it is may a solution for this.

Also, as the UBI/UIFS case may show, it is not always a trivial job
to do such a sync, as concepts in Linux changes ...

bye,
Heiko
[1] https://github.com/hsdenx/tbot
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