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

[Boris Brezillon]

Hi Scott,

On Tue, 03 May 2016 00:06:45 -0500
Scott Wood <oss at buserror.net> wrote:

> On Mon, 2016-04-25 at 22:53 +0200, Boris Brezillon wrote:
> > On Mon, 25 Apr 2016 13:36:46 -0400
> > Tom Rini <trini at konsulko.com> wrote:
> >   
> > > 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.
> > >   
> > 
> > Okay, so this means I should be the one back-porting Linux changes into
> > U-Boot? I was planning on porting my current work on the sunxi NAND
> > driver (including all the core dependencies) and submitting it to
> > U-Boot, but honestly, I don't see how I can keep things in sync in the
> > long run. From my experience, porting things to U-Boot is never as
> > easy at it seems, and I don't think I'll have the time to maintain that
> > by myself. Scott, what's your policy regarding Linux -> U-Boot syncs?
> > Can I expect some help from your side?  
> 
> I usually do syncs when someone complains about needing a sync.  Every release
> seems a bit much.  I'll try to do one soon.

Sorry to bother you with that, but can I ask when you plan to do this
sync (I guess you'll sync with 4.6)? As I explained, I depend on
features introduced in 4.6 to make the sunxi NAND driver usable on
sunxi based boards (the concept of data randomizer/scrambler is
required on some MLC NANDs, and most Allwinner boards embed this
kind of NAND chips).

Don't hesitate to let me know if you need some help.

Thanks,

Boris

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