Re: Converting MIPS to Device Tree

[David Daney <ddaney@caviumnetworks.com>]

On 06/10/2011 11:57 AM, Ralf Baechle wrote:
> On Tue, Jun 07, 2011 at 04:22:16PM -0700, David Daney wrote:
>
>>> use a parameter like "devtree=<virtual-address>" on the command line, passed
>>> in any way the bootloader likes.
>>
>> Some  u-boots for non-mips platforms pass it in the environment of
>> the bootm protocol.
>>
>> I would say to pass the pointer to the DTB in the environment, but
>> not all platforms (like powertv) have an environment.  So I guess
>> the command line has to do.
>
> 3 steps:
>
>    1) Use command line argument for DT
>    2) Iff 1) fails, use DT specified by environment

I'm OK with this as long as we can define 'the environment' to include 
what I am currently doing on Octeon.


>    3) Iff 1) and 2) fail, use builtin DTB.
>
>> Also I think we should pass the physical address of the DTB, not the
>> virtual address.  It would be the kernel's responsibility to figure
>> out what the virtual address is.
>
> I like the basic idea - but ...  Most firmware will only use KSEG0 / XKPHYS
> mappings so there should be no aliasing issue but still there could be
> conflicting cache modes.  So we should also specify that firmware should
> writeback and invalidate the DTB from caches.
>
>    Ralf
>