Re: [ORLinux] [PATCH] openrisc: Add DTS and defconfig for DE0-Nano

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On 11/15/2013 12:39 PM, Olof Kindgren wrote:
2013/11/15 Jonas Bonn <jonas@xxxxxxxxxxxx>

On 11/15/2013 11:22 AM, Geert Uytterhoeven wrote:

This should probably be "altera,de0_nano".  We also need to put a version


"terasic,de0_nano"? The board says "Designed and manufactured by Terasic".
Hmm, the sticker on the box says "Altera DE0-Nano".


Good question...



terasic makes more sense than Altera. Altera just provides one of the
components on the board

OK, terasic is probably better then.




Version number needed.  OpenCores wanted "projectname-rtlsvn###" where
###
is the SVN commit number of the RTL directory in the project's source
repository.


That's gonna need some information diving, as Stefan's orpsoc git
repositories
only contains references to orpsocv2 git-svn-ids, not the svn ids of
the original
component repositories.


Stefan?  Where's the "official" home of these cores nowadays?  Have they
been modified since they were copied from OpenCores into orpsocv2?


Most cores are fetched directly from OpenCores SVN. Out of these, some are
patched on the fly by ORPSoC before they are being built. Most of the new
cores are only available on github

The version number is important in order to ensure _driver_ compatibility. As long as the patches don't make changes that requires changes to the Linux driver then it's OK to just put the SVN version number on them. If incompatible changes are being made, then we really need to find a "home" for these cores so that we can manage their version numbers in some way.


More generally, can Linux use out-of-tree DTS files in an easy way? It's
handy to have them in the kernel, but the best fit might actually be to put
them in the corresponding orpsocv3 system directory. That would also make
it easier to have separate device trees for differently configured FPGAs
(they are reprogrammable after all).

Yes, the DTS files don't really belong in the kernel tree at all. They belong "near the hardware". For these FPGA projects it definitely makes sense to keep (or automatically generate) the DTS files in the RTL build system, i.e. orpsoc.

We generally build the DTB into the kernel image itself, but that's not really necessary. You just need to get the DTB into memory and pass the kernel a pointer to it. If you can find some way to build the DTB into the FPGA image (block RAM?) then you've got a self-describing HW image: have the OpenRISC core initialize itself with r3 containing the address of the DTB and jump to the kernel entry point (reset vector) and everything should just work. If you put device tree logic into newlib as well then you can use this HW description for (other) bare metal apps, as well.

The device tree compiler is in the Linux kernel tree... but it's usable outside of the Linux build system, as well. You'll find the binary in script/dtc/dtc in the kernel tree... run it with --help to get an idea of how it's used. It really isn't supposed to have anything to do with Linux at all; it's a generic tool for a generic HW description.

/Jonas




//Olof

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