[U-Boot] MIPS UHI spec

[Daniel Schwierzeck]

Am 09.03.2015 um 18:04 schrieb Andrew Bresticker:
> Hi Daniel,
> 
> On Thu, Feb 26, 2015 at 4:37 AM, Daniel Schwierzeck
> <daniel.schwierzeck at gmail.com> wrote:
>> 2015-02-26 11:17 GMT+01:00 Paul Burton <paul.burton at imgtec.com>:
>>> On Thu, Feb 19, 2015 at 01:50:23PM +0000, Matthew Fortune wrote:
>>>> Hi Daniel,
>>>>
>>>> The spec for MIPS Unified Hosting Interface is available here:
>>>>
>>>> http://prplfoundation.org/wiki/MIPS_documentation
>>>>
>>>> As we have previously discussed, this is an ideal place to
>>>> define the handover of device tree data from bootloader to
>>>> kernel. Using a0 == -2 and defining which register(s) you
>>>> need for the actual data will fit nicely. I'll happily
>>>> include whatever is decided into the next version of the spec.
>>
>> this originates from an off-list discussion some months ago started by
>> John Crispin.
>>
>> (CC +John, Ralf, Jonas, linux-mips)
>>
>>>
>>> (CC +Andrew, Ezequiel, James, James)
>>>
>>> On the talk of DT handover, this recent patchset adding support for a
>>> system doing so to Linux is relevant:
>>>
>>>     http://www.linux-mips.org/archives/linux-mips/2015-02/msg00312.html
>>>
>>> I'm also working on a system for which I'll need to implement DT
>>> handover very soon. It would be very nice if we could agree on some
>>> standard way of doing so (and eventually if the code on the Linux side
>>> can be generic enough to allow a multiplatform kernel).
>>>
>>
>> to be conformant with UHI I propose $a0 == -2 and $a1 == address of DT
>> blob. It is a simple extension and should not interfere with the
>> various legacy boot interfaces.
> 
> Just to be clear, is $a1 expected to be the physical or virtual
> (KSEG0) address of the DTB?
> 

U-Boot currently uses KSEG0 addresses for kernel entry and initramfs.
Therefore the DTB address would be also KSEG0. But I'm not sure if it is
correct for MIPS64. Shouldn't the kernel sanitize the DTB address anyway
like it's done with initramfs? Maybe Matthew or others could comment.

-- 
- Daniel