[meta-xilinx] meta-xilinx: jethro Branch

[Nathan Rossi]

On Tue, Nov 24, 2015 at 8:53 PM, Norbert Belfin <nbelfin at radiodata.biz> wrote:
> Hello,
>
> first, thanks for your great work. Second, my questions: what does
> 'support for the linux-yocto 4.1 kernel mean'? Can I use it like the
> linux-xlnx 4.0 kernel together with files generated by Vivado 2015.3?

'Support for the linux-yocto 4.1 kernel' means that the machines in
the meta-xilinx layer can be built using the linux-yocto 4.1 kernel
(some default to it). A bbappend in the layer adds the necessary
configuration to apply a functional kernel configuration. And I have
done some functional (although not anywhere near complete) testing
such that there does not appear to be any regressions or missing
functionality (which is available in the kernel).

>From a Yocto/OE standpoint you can use it pretty much how you use the
linux-xlnx kernels. However regarding files generated by Vivado
2015.3, it depends on which files. If you are referring to just the
device-tree, then chances are there will be in-compatibilities.

> What is the difference between the linux-xlnx kernel and the linux-yocto
> kernel (with the bbappends)?

>From a specifically Xilinx hardware use case the differences are
primarily driver support, the linux-yocto kernel is from a Zynq driver
standpoint essentially equivalent to the mainline kernel. This means
some important drivers are not available.

At a bbappends level there are slight differences (mainly to do with
how the git repo is sourced), however linux-xlnx includes the
linux-yocto.inc recipe infrastructure and works with the kmeta and
KERNEL_FEATURES/.scc/etc for configuration. So all the useful features
that linux-yocto has you can use with linux-xlnx, a lot of which is
documented in the kernel-dev manual
(http://www.yoctoproject.org/docs/latest/kernel-dev/kernel-dev.html).

> Background: we use a zynq xc7z010. Currently the development is done
> with vivado 2015.2 and 2015.3. The kernel we are using is linux-xlnx 4.0
> from the master branch. Is there a reason why not to use linux-yocto 4.1

Driver support is pretty much the only reason why you would require
linux-xlnx. As mainline and linux-yocto lag behind compared to
linux-xlnx on support for specific Zynq hardware, specifically (for
4.1) the big ones that you probably need are:

* devcfg / PL loading from kernel
* QSPI
* NAND/SMC
* emacps, although there is a ethernet driver available (macb) but it
is missing some zynq features like MMI bridging support, and there is
a performance difference (emacps has higher throughput)

If you don't need these drivers I highly recommend you take a look at
the linux-yocto kernel, even if just for curiosity.

> kernel. If there are no reasons, at which file I can say which kernel to
> use. At time I only now how to set which version to use for linux-yocto
> or linux-xlnx, but not which of both should be active.

The two lines you need in your local.conf or in your <machine>.conf are:

PREFERRED_PROVIDER_virtual/kernel = "linux-yocto"
PREFERRED_VERSION_linux-yocto = "4.1%"

Regards,
Nathan

> Thanks for your time.
> Greetings
>      Norbert
>
> Am 23.11.2015 um 09:57 schrieb Nathan Rossi:
>> Hi All,
>>
>> The jethro branch in meta-xilinx has been created for the 2.0 release
>> of Yocto/OE.
>>
>> This version of the meta-xilinx layer contains the following
>> significant features:
>>  * Updated to support Yocto/OE 2.0
>>  * Updates and improvements to the MicroBlaze tunes to add support for
>> Big-Endian
>>  * Added the qemumicroblaze-s3adsp1800 machine (For MicroBlaze
>> Big-Endian testing)
>>  * Update for GCC 5.2 support (specifically MicroBlaze)
>>  * Support for the linux-yocto 4.1 kernel
>>  * Support for the linux-xlnx 3.19 kernel (xilinx-v2015.2.03)
>>  * Update u-boot-xlnx to v2015.04 (xilinx-v2015.2)
>>  * Change ep108-zynqmp to use mainline u-boot/QEMU and linux-yocto,
>> dropping '*-zynqmp-mainline' recipes
>>
>> As usual the layer can be obtained via the git repository at
>> git.yoctoproject.org:
>>  * git  - git://git.yoctoproject.org/meta-xilinx
>>  * http - http://git.yoctoproject.org/git/meta-xilinx
>>  * cgit - http://git.yoctoproject.org/cgit/cgit.cgi/meta-xilinx/
>>
>> Regards,
>> Nathan
>
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