[PATCH 2/2] arm: mvebu: Espressobin: Setup MTD partitions when booting kernel

["Pali Rohár" <pali@kernel.org>]

On Thursday 20 August 2020 10:17:55 Stefan Roese wrote:
> On 20.08.20 09:40, Pali Roh?r wrote:
> > On Thursday 20 August 2020 07:02:18 Stefan Roese wrote:
> > > Can't you just use "mtdparts=" kernel cmdline parameter instead to pass
> > > the MTD layout to the kernel?
> > 
> > Maybe it is possible too, I have not tried it.
> > 
> > I thought that more common is to update DTS file by uboot when loading
> > kernel as it is already done e.g. for ethernet MAC address on
> > Espressobin.
> 
> Updating the MAC address is very common, yes. But passing the
> MTD partition layout via the mtdparts= cmdline is also very
> common and used very frequently. From my experience, its the
> defacto recommended method to pass this info and also easier than
> generating these DTS lines via some code.
> 
> Please take a look at the mtdparts U-Boot command and its usage
> in other targets.
> 
> > Also I see that uboot has function fdt_fixup_mtdparts() via
> > CONFIG_FDT_FIXUP_PARTITIONS option which do this, but uses uboot MTD
> > code which IIRC cannot initialize SPI NOR.
> 
> Why not?

I had an impression that U-Boot does not support.

> SPI NOR is also integrated into the U-Boot MTD world as
> well. Please see this GARDENA MT7688 target, which uses SPI NOR &
> SPI NAND:

Ok, I'm going to look at it.

> > Anyway, updating DTS has advantage that it is not needed to update
> > existing boot scripts for OS. There are more distributions for
> > Espressobin which have own boot scripts stored on SD card for loading
> > kernel. And therefore to use command line parameters it would be needed
> > to update all of them.
> 
> I see. This is an argument I understand. But can't you use the common
> fdt_fixup_mtdparts() then?
> 
> > And I see there another problem. For specifying size of mtd partitions
> > in command line, it is required to know offsets of those partitions. And
> > e.g. uboot env partition depends on CONFIG_ENV_OFFSET option which is
> > not available for uboot boot script code.
> > 
> > But if you have other idea, I'm open to also other solutions.
> 
> I have not investigated a multi-distribution solution here. Perhaps
> the common fdt_fixup_mtdparts() is able to handle this?

In case U-Boot would see MTD SPI partitions, then fdt_fixup_mtdparts()
should work.