[OpenWrt-Devel] [PATCH 0/3] ipq806x: add NAND flash support

Mathieu Olivari mathieu at codeaurora.org
Fri Aug 7 12:50:36 EDT 2015

Actually, I was asking myself the same questions yesterday. I was leaning
towards dts for the reasons you mention below as well; the problem is on ref
designs, there is no "standard" layout. The flash layout changes with time
(an AP148 with an old boot binary blob will have a different layout than the
same AP148 with a new boot image), sometimes with a certain application
(some boots will have an SMEM with 2 kernels & 2 rootfs for dual
partitioning). For this reason, and on ref designs, it'd be easier to have
one dts and the kernel adapting at run-time, than multiplying the dts files
and having to pick the right one based on your current SMEM content.

I would agree that it's the exception though; on most retail routers, you
would have one SMEM per SKU, i.e. one layout per dts.

I'm thinking the most flexible way would probably to have the opportunity in
dts to select between "dynamic" smem partitioning, or regular "fixed"
partitioning. Not sure if something like this has ever been done in the
past; but we could explore it.


-----Original Message-----
From: Felix Fietkau [mailto:nbd at openwrt.org] 
Sent: Friday, August 07, 2015 2:11 AM
To: Mathieu Olivari; jogo at openwrt.org
Cc: openwrt-devel at lists.openwrt.org
Subject: Re: [PATCH 0/3] ipq806x: add NAND flash support

On 2015-08-07 04:28, Mathieu Olivari wrote:
> This patch serie adds support for the integrated NAND flash controller 
> available on AP148. Most of the patches are backported from LKML, with 
> minor modifications.
> This is kernel level support & enablement for now. Support for proper 
> MTD partitioning will come later and will be necessary to boot from 
> it.
Do you plan on porting the smem stuff for partitioning that QSDK uses, or do
are you going to add partitions to the device tree file?
Unless there's a good reason to avoid it, I'm leaning towards the latter, to
give our kernel more control over what's going on.
For example, I'd like to call the partition with the kernel/fs 'ubi'
instead of 'rootfs', since rootfs is already used to auto-select the root
filesystem partition for auto-mounting.

- Felix
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