[yocto] [meta-raspberrypi][PATCH v2] linux-raspberrypi-rt: add

[Andrei Gherzan]

On Thu, Jan 05, 2017 at 10:54:01PM -0500, Trevor Woerner wrote:
> On Thu, Jan 5, 2017 at 4:59 PM, Paul Barker <paul at paulbarker.me.uk> wrote:
> > On Thu, 5 Jan 2017 15:16:19 -0500
> > Trevor Woerner <twoerner at gmail.com> wrote:
> >
> >> On Thu 2017-01-05 @ 07:33:38 PM, Paul Barker wrote:
> >> > On Thu,  5 Jan 2017 12:42:29 -0500
> >> > Trevor Woerner <twoerner at gmail.com> wrote:
> >> >
> >> > > Add an -rt kernel recipe for Raspberry Pi that includes the FIQ patch which
> >> > > adds stability to the -rt kernel (with full preemption enabled) and is an
> >> > > improvement to simply disabling FIQ on the kernel cmdline.
> >> > >
> >> > > Signed-off-by: Trevor Woerner <twoerner at gmail.com>
> >> > > ---
> >> > >
> >> > > changes since v1:
> >> > >   - use "make savedefconfig" to generate the defconfig instead of just
> >> > >     using the full .config
> >> > >
> >> > >  .../0001-fix-dtbo-rules.patch                      |    44 +
> >> > >  .../FIQ_PREEMPT_RT_on_raspi.patch                  |   310 +
> >> > >  .../linux/linux-raspberrypi-rt-4.4/defconfig       |  1249 +
> >> > >  .../patch-4.4.32-rt43.patch                        | 31403 +++++++++++++++++++
> >> > >  recipes-kernel/linux/linux-raspberrypi-rt_4.4.bb   |    55 +
> >> > >  5 files changed, 33061 insertions(+)
> >> > >  create mode 100644 recipes-kernel/linux/linux-raspberrypi-rt-4.4/0001-fix-dtbo-rules.patch
> >> > >  create mode 100644 recipes-kernel/linux/linux-raspberrypi-rt-4.4/FIQ_PREEMPT_RT_on_raspi.patch
> >> > >  create mode 100644 recipes-kernel/linux/linux-raspberrypi-rt-4.4/defconfig
> >> > >  create mode 100644 recipes-kernel/linux/linux-raspberrypi-rt-4.4/patch-4.4.32-rt43.patch
> >> > >  create mode 100644 recipes-kernel/linux/linux-raspberrypi-rt_4.4.bb
> >> > >
> >> >
> >> > Would it be possible to point SRC_URI at kernel.org [1] instead of
> >> > including the whole patch in meta-raspberrypi? It feels a bit much to
> >> > me to include a >1MB patch file.
> >> >
> >> > [1]: https://www.kernel.org/pub/linux/kernel/projects/rt/4.4/older/patch-4.4.32-rt43.patch.gz
> >>
> >> The "virgin" -rt patch from kernel.org doesn't apply cleanly. First off there
> >> is a slight version mismatch and secondly this is the raspberrypi kernel, not
> >> a pure upstream kernel.
> >>
> >> Is there a way to patch a patch before it gets applied? If it could be
> >> fetched from kernel.org then patched before applying that would be ideal!
> >> The diff isn't that big; it's sad to have to provide a >1MB patch for such
> >> a small tweak. I guess that's why the yocto kernels/patches have their own
> >> repositories on yoctoproject.org?
> >
> > I think it depends how you want to maintain it going forward. With
> > frequent upgrades to linux-raspberrypi I can see that >1MB patch being
> > modified very often and I'm not sure how good it will be for the git
> > repository size and efficiency.
>
> Okay, agreed.
>
> > A linux-raspberrypi-rt repository on GitLab[1] or some other git hosting
> > service may be a good idea. I can see this having value outside the
> > OpenEmbedded/Yocto Project world, especially if the vanilla -rt patches
> > don't directly apply to linux-raspberrypi. If you decide to go this
> > route and need any support to make it happen, let me know and I'll see
> > what I can do.

I vote for a rt repository externally maintained too. Having it here
might not be the best idea on the long term.

>
> Sounds good... and Wow! GitLab looks awesome! I guess I'll look at how
> the yocto kernels are managed and see if it applies.
>

Does it? :)

> > Also, are you thinking of moving the -rt recipe to the 4.9 series when
> > upstream linux-raspberrypi declares that stable?
>
> Yes.
>
> > When they declared 4.4
> > stable they stopped updating the 4.1 series pretty much immediately. I'm
> > currently investigating whether there is any value in maintaining the
> > 4.4 series ourselves after upstream moves on.
>
> I want to see how managing one goes.
> --
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--
Andrei Gherzan
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