2015-02-26 19:23 GMT+01:00 Andrew Bresticker abrestic@chromium.org:
Hi,
On Thu, Feb 26, 2015 at 4:37 AM, Daniel Schwierzeck daniel.schwierzeck@gmail.com wrote:
2015-02-26 11:17 GMT+01:00 Paul Burton paul.burton@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.htmlI'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).
+1. I would like to see this happen as well.
to be conformant with UHI I propose $a0 == -2 and $a1 == address of DT blob. It is a simple extension and should not interfere with the various legacy boot interfaces.
U-Boot mainline code is almost ready for DT handover. I have prepared a patch [1] which completes it by implementing my proposal.
Hmm... we decided to follow the ARM convention here ($a0 = 0, $a1 = -1, $a2 = physical address of DTB), which is also what the BMIPS platform (submitted by Kevin) is using for DT handover. Is there already a platform using the protocol you described?
no, but with its publication the MIPS UHI spec is kind of official. AFAIK patches to support UHI in gcc, gdb, U-Boot etc. are already submitted or prepared. Matthew suggested that new boot protocols should be compliant with UHI. I think the ARM convention does not fit to UHI.
It's still early enough that we could change the DT handover for Pistachio, but it would be good to agree on something soon.
Thanks, Andrew