[meta-xilinx] Devicetrees and kernel version

Nathan Rossi nathan.rossi at xilinx.com
Wed Feb 19 17:46:22 PST 2014


> -----Original Message-----
> From: meta-xilinx-bounces at yoctoproject.org [mailto:meta-xilinx-
> bounces at yoctoproject.org] On Behalf Of Elvis Dowson
> Sent: Wednesday, February 19, 2014 7:56 AM
> To: Philip Balister
> Cc: meta-xilinx Mailing List
> Subject: Re: [meta-xilinx] Devicetrees and kernel version
> 
> Hi Philip,
> 
> I would think that any dts files that go into conf/machine/board,
> should be generic enough to work across multiple IP cores
> revisions, by setting it to the lowest compatible IP core revision
> number.

The kernel tends to be under a bit of churn with regards to DTS's and Zynq. An unfortunate effect caused by maintaining a fork of the kernel and taking too long to upstream drivers.

I've tried to mitigate as many of those issues as possible with the zynq-7-base.dtsi.
https://github.com/Xilinx/meta-xilinx/blob/master/conf/machine/boards/common/zynq-7-base.dtsi

MicroBlaze however should be relatively stable, except for maybe new drivers.

> 
> I think if that you start adding conf/machine/board/linux-xlnx_3.13
> it would start messing up the norm, i.e. kernel version specific files
> normally reside in the kernel recipe folder.

Not necessarily, we have per kernel version defconfigs in the conf/machine/board/common/ in meta-xilinx.
https://github.com/Xilinx/meta-xilinx/tree/master/conf/machine/boards/common

> 
> Another point to reflect upon, in terms of alternatives, is if we had
> adopted the linux yocto LTSI approach, each per kernel git repo
> could maintain its own device tree file.

Unfortunately that wouldn't scale to well for user input DTS's. (Which is common for MicroBlaze and Zynq, but not really for the common chips/boards/etc linux-yocto targets)

> 
> Regards,
> 
> Elvis Dowson
> 
> On Feb 19, 2014, at 1:40, Philip Balister <philip at balister.org> wrote:
> 
> > I'm working on creating a recipe to build master-next and calling it
> > linux-xlnx_3.13.bb.
> >
> > Everything is straightforward, except for how the devicetree files are
> > handled.
> >
> > Does anyone have an idea how we can have per kernel version devicetree
> > files in meta-xilinx? "Normally" we would put them in a version specific
> > directory with the kernel stuff. But meta-xilinx stores them in the
> > conf/machine directory. Should I just do a conf/machine/board/foo-3.13/
> > directory and use that for the devicetree files?

Do you have the fragment or entire file that needs to be modified? Curious if it can't just be worked into the main zynq-7-base.dtsi.

It might make sense to have kernel version specific dtsi files that sit between the baseline zynq-7-base.dtsi, they could change the compatible fields, etc.

Regards,
Nathan





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