Re: [PATCH v1 0/3] fdt: Fix mtparts fixup

[Miquel Raynal <miquel.raynal@bootlin.com>]

Hi Tom,

trini@konsulko.com wrote on Fri, 13 Jan 2023 14:34:11 -0500:

> On Fri, Jan 13, 2023 at 07:45:44PM +0100, Francesco Dolcini wrote:
> 
> > From: Francesco Dolcini <francesco.dolcini@toradex.com>
> > 
> > Recently we had a boot regression on colibri-imx7 because of a cleanup change
> > on Linux imx7.dtsi setting nand controller node #size-cells from 1 to 0.
> > 
> > Because of that Linux partition parser was no longer able to properly
> > parse the OF partitions leading to a boot failure, the above change was
> > reverted in the meantime as an immediate workaround, but some improvement
> > is required on both Linux and U-Boot.
> > 
> > This change improve the U-Boot part of it, #size-cell is set to 1 when
> > it has an invalid value. This has the limitation to work only with devices
> > smaller than 4GiB. In general the suggestion from the Linux MTD maintainer would
> > be to just deprecate using this U-Boot function and pass the MTD partitions
> > from the command line, unless they are statically defined in the DTS file
> > in the first place.
> > 
> > This series therefore convert colibri-imx6ull and colibri-imx7 to pass the
> > partition list from the command line instead of fixing up the DT.
> > 
> > Link: https://lore.kernel.org/all/20221202071900.1143950-1-francesco@dolcini.it/
> > Link: https://lore.kernel.org/all/Y4dgBTGNWpM6SQXI@francesco-nb.int.toradex.com/  
> 
> My higher level question / concern here is, is using one of the dts
> partition schemes still valid / preferred, or should everyone now have
> reverted to passing via the kernel command line?  If device tree still,
> is mtd/partitions/fixed-partitions.yaml the one to follow or something
> else?

I don't think we can "prefer" one mode over the other between cmdline
and DTS. Both should work pretty well. Of course on the cmdline you can
only define fixed partitions and many devices require more advanced
parsers, which are only available through DTS, but for simple
partitions, it works totally okay.

The only thing that I would like to avoid is the need to write code in
the bootloaders to tweak the FDT in order to add partitions. That is
clearly not needed, error prone, and do not follow evolution of the
"standard", as we just discovered.

Thanks,
Miquèl