[U-Boot] [PATCH 12/31] board_f: Add new function to allow runtime DTB selection

[Lukasz Majewski]

On Thu, 9 Mar 2017 08:08:20 -0500
Tom Rini <trini at konsulko.com> wrote:

> On Thu, Mar 02, 2017 at 01:04:16PM -0600, Franklin S Cooper Jr wrote:
> 
> > Runtime U-boot dtb selection is generally a two step process. First
> > step is to simply use an initial generic dtb. The second step is to
> > select the dtb and perhaps execute additional code ones U-boot
> > knows what board it is running on. Embedded_dtb_select handles the
> > second step by allowing board specific code to run and perform what
> > ever necessary configuration that is needed.
> 
> So I'm not 100% sure on how to proceed here exactly.  We have a few
> things to consider.  First, I bet the generic dtb is good enough for
> loading up and booting to Linux (and loading/passing a different,
> complete and board specific DTB).  Second, we have the (reasonable)
> set of patches and discussion to make the DTB that we use available
> easily so that it could be passed on to Linux (or EFI apps or
> whatever). So, this is probably the right thing to do in the long
> run, but is also another data point in the "but we need to think and
> talk about if some platforms really shouldn't be shipping their full
> FT on the HW somewhere".

It might also happen that somebody would like to have one "blessed"
u-boot binary stored in one place and then only change u-boot DTB stored
on another memory region (like eMMC, NOR).

The above also seems like a valid use case, especially when one wants to
support device for a long time (many DTBs) and avoid uncontrolled grown
of final u-boot.img binary size (as this is now the case for TI).

> 
> > 
> > Signed-off-by: Franklin S Cooper Jr <fcooper at ti.com>
> [snip]
> > +config DTB_RESELECT
> > +	bool "Support swapping dtbs at a later point in boot"
> > +	depends on FIT_EMBED
> > +	default n
> 
> This is the default, you can drop it.
> 




Best regards,

Lukasz Majewski

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