Setting NAND timings parameters (Re: [RFC/PATCH v2] mtd: nand: pxa3xx: Remove redundant device probing)

[Ezequiel Garcia]

On Tue, Nov 26, 2013 at 03:17:09PM -0800, Brian Norris wrote:
> 
> I see that the removal of your driver-specific device table stalled on
> this issue. Are you planning on picking it up?
> 

Kind of. I'd love to fix this ugly code, but have lots of others items
on this driver's TODO list.

> On Tue, Sep 24, 2013 at 06:46:54PM -0300, Ezequiel Garcia wrote:
> > On Tue, Sep 10, 2013 at 04:14:25PM +0200, Daniel Mack wrote:
> > > > 
> > > > Right. However, since we can easily add support to configure every controller
> > > > parameter (right?) this shouldn't be a problem.
> > > > 
> > > > What do you think of this change, Daniel?
> > > 
> > > I always thought that this detail of the pxa nand driver is ugly :) But
> > > I'd say before it can be merged, you need to provide code to set the
> > > timing from parameters obtained from generic part. Are you working on
> > > this? I'd happily test more patches.
> > > 
> > 
> > Returning to this point: it seems we have two different cases: ONFI-compliant
> > devices and non-ONFI.
> > 
> > For the ONFI, we can have a timings parameter table with some index according
> > to the ONFI timing mode available or user-selected. This table could be
> > generic (as in Matthieu Castet patch [1]) or driver specific (as in
> > denali driver).
> 
> It looks like denali just uses a module parameter so the user can select
> an ONFI timing mode. This isn't flexible or generically useful and
> shouldn't be encouraged on new code.
> 

Agreed.

> If more drivers need timing information like this, I would like to see a
> generic implementation like Matthieu's (although his can be improved, I
> think). It's also worth noting that his code only gets information for
> the SDR timing modes, not DDR. I don't know if any hardware is utilizing
> DDR modes (I haven't tested it on mine), but it's worth considering
> if/how this would fit into the framework.
> 

OK, I'll see if I can push my previous work on this. I have a modified
patch in some branch around here.
-- 
Ezequiel García, Free Electrons
Embedded Linux, Kernel and Android Engineering
http://free-electrons.com