[Letux-kernel] 4.16 onenand

Andreas Kemnade andreas at kemnade.info
Tue Apr 10 07:27:51 CEST 2018

On Mon, 9 Apr 2018 08:59:03 +0200
"H. Nikolaus Schaller" <hns at goldelico.com> wrote:

> Hi Andreas,
> > Am 09.04.2018 um 07:50 schrieb Andreas Kemnade <andreas at kemnade.info>:
> > 
> > On Sun, 8 Apr 2018 22:36:12 +0200
> > "H. Nikolaus Schaller" <hns at goldelico.com> wrote:
> >   
> >> Hi,
> >> I just recognised that this
> >>   
> >>> Am 07.04.2018 um 22:41 schrieb Andreas Kemnade <andreas at kemnade.info>:
> >>> 
> >>> Hmm, using one letux dtb, separately compiled. And then compile
> >>> on plain mainline. There should be no reason why onenand should not
> >>> work on mainline.    
> >> 
> >> may be wrong.
> >> 
> >> If for example a patch between 4.16-rc0 and 4.16-rc1 changes some
> >> omap3 SoC support driver (clocks, hwmods etc.) this might need
> >> a change in omap3-something.dtsi as well.
> >>   
> > Well, old dtbs have to be compatible,  
> Hm. I am still not convinced that this assumption is correct. It is
> like asking for some old module.ko to be compatible.
> The reason I see is that there may be hidden changes we have no
> responsibility for (and do not look for).
Well, you remember the comments when you try to upstream something
dtb-related. Compatibility of newer kernels to older dtb was always a
requirement and dtb on devices considered as cast in stone.
There were talks at FOSDEM considering them to be even more part of the
device. And here it seems that we have forgotten

So if the old dtb does not work with the newer kernel, it is a bug.
If someone introduced a problem in dtb itself it is another bug.
What is a risk: Stuff which is not mainlined and compatibly breaks are
not noticed.

Our onenand dtb section was missing the compatibly string which
is such an example:
commit 18b1b03e35c85589ddaea0fcdab72115e6df838e
Author: H. Nikolaus Schaller <hns at goldelico.com>
Date:   Sat Feb 10 16:16:15 2018 +0100

    ARM: dts: OMAP2+: Add compatible property to onenand node

I have done some experiments but not much. But I have found out that
having a working
strings /dev/mtd0ro

does not mean that ubiattach also works.

So I could reproduce your problems.

I had somehow trouble to have a working fb console on 4.15 mainline with
gta04a5. No problem with letux3704. 

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