[Lenny400] [Mipsbook-devel] Reviewing the Ingenic board initialisation code

Dr. H. Nikolaus Schaller hns at goldelico.com
Wed Jun 10 07:31:06 CEST 2015


Am 10.06.2015 um 01:45 schrieb Daniel Glöckner <daniel-gl at gmx.net>:

> On Tue, Jun 09, 2015 at 07:21:00PM +0200, Dr. H. Nikolaus Schaller wrote:
>>> I imagine that booting a single payload with appended DT information is 
>>> probably desirable in many different environments. Indeed, I thought that this 
>>> was being widely done on the supported platforms already.
>> 
>> Well, in my experience it is easier to have a common binary uImage that
>> fits all devices and just change the device tree file that is loaded by u-boot.
>> 
>> This avoids the step of making and publishing n different uImages for n devices.
>> 
>> Just n different small DTB files. And, DTB should become stable, i.e. survive
>> kernel upgrades so that only the uImage needs to be swapped.
>> 
>> Finally, the file name of the DTB can match the device name.Since U-Boot is
>> usually also device specific it is easier to distribute an U-Boot+DTB bundle
>> and a separate kernel image.
> 
> U-Boot writes some values into the device tree, like the base address and
> size of the RAM. This allows sharing of the device tree across boards with
> slight variations. You can also do arbitrary changes to the device tree
> from boot scripts with U-Boot’s fdt command if the tree is a separate file.

I guess (without looking at it) that our U-Boot installed in NAND is too old
to be able to manipulate fdt (dtb) files. It was deployed together with a 
2.4.? kernel.

But we can stay with merged DT that provides the correct RAM size.

BR,
Nikolaus



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