Re: [PATCH 1/6] ARM: dts: am335x-phycore-som: Update NAND partition table

[Teresa Remmet <t.remmet@phytec.de>]

Hello Brian,

Am Donnerstag, den 05.01.2017, 09:56 -0800 schrieb Brian Norris:
> On Thu, Jan 05, 2017 at 09:18:45AM -0800, Tony Lindgren wrote:
> > 
> > * Tony Lindgren <tony@atomide.com> [170105 07:37]:
> > > 
> > > * Teresa Remmet <t.remmet@phytec.de> [170105 06:57]:
> > > > 
> > > > To improve NAND safety we updated the partition layout.
> > > > Added barebox backup partition and removed kernel and oftree
> > > > partition. They are kept in ubi now.
> > > What about the users with earlier partition tables?
> > > 
> > > Please read about "flag day" changes, typically they are not
> > > acceptable.
> > Adding Brian and Adam to Cc. Can you guys come up with some
> > solution on this?
> I don't have much context for this thread, and no I don't plan to
> solve
> your problems for you. But I can provide tips!
> 
> > 
> > I'm suggesting we leave the kernel nodes empty and let u-boot
> > populate them, so maybe you guys can discuss this on the related
> > lists.
> That's an option. I've worked with platforms that did something like
> this, and that's really one of the only ways you can handle putting
> partition information in the device tree. You're really hamstringing
> yourself when you put all the partition information in the device
> tree.
> And it's just dumb once that gets codified in the kernel source tree.
> 

In our case the bootloader does pass the partition table to the kernel.
So it gets overwritten anyway. This was just more for backup, 
if someone uses a different bootloader. But I'm fine with removing the
nand partition table completely from the kernel device tree.
Same with the SPI nor partition table.

I will send patches for this.

Regards,
Teresa

> The best solution would be to try to migrate away from static device
> tree representations of partition info entirely. UBI volumes are best
> where possible. If not, then some other kind of on-flash data
> structures
> (along the lines of a GPT) with a corresponding MTD partition parser
> is
> an OK alternative. Unfortunately, there isn't any good standard
> format
> for this on MTD, so it's typically all custom -- and so people use
> the
> easiest approach: device tree. And it's even more difficult with
> NAND,
> which has reliability problems, especially with static data (e.g.,
> read
> disturb).
> 
> Anyway, the parser solution is helpful only if one can properly fix
> the
> "flag day" first. And it requires a little bit more work to be
> generally
> useful; I posted some work for this over a year ago, but bikeshedding
> brought it down.
> 
> > 
> > The rest of the series looks fine to me so applying it into
> > omap-for-v4.11/dt.
> Brian
> 
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