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Re: [U-Boot] MIPS UHI spec

To: Paul Burton <>
Subject: Re: [U-Boot] MIPS UHI spec
From: Daniel Schwierzeck <>
Date: Thu, 26 Feb 2015 13:37:28 +0100
Cc: Matthew Fortune <>, "" <>, Andrew Bresticker <>, Ezequiel Garcia <>, James Hartley <>, James Hogan <>, John Crispin <>, Jonas Gorski <>, Ralf Baechle <>,
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2015-02-26 11:17 GMT+01:00 Paul Burton <>:
> 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:
>> 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:
> 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.

U-Boot mainline code is almost ready for DT handover. I have prepared
a patch [1] which completes it by implementing my proposal.


- Daniel

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