Re: [ANNOUNCE] v5.4.10-rt5

[Paul Thomas <pthomas8589@gmail.com>]

On Tue, Jan 14, 2020 at 4:04 PM Gene Heskett <gheskett@shentel.net> wrote:
>
> On Tuesday 14 January 2020 12:15:37 Paul Thomas wrote:
>
> > On Tue, Jan 14, 2020 at 11:24 AM Gene Heskett <gheskett@shentel.net>
> wrote:
> > > On Tuesday 14 January 2020 08:54:30 Paul Thomas wrote:
> > > > On Sun, Jan 12, 2020 at 9:44 PM Gene Heskett
> > > > <gheskett@shentel.net>
> > >
> > > wrote:
> > > > > On Friday 10 January 2020 15:14:30 Sebastian Andrzej Siewior
> wrote:
> > > > > > Dear RT folks!
> > > > > >
> > > > > > I'm pleased to announce the v5.4.10-rt5 patch set.
> > > > > >
> > > > > > Changes since v5.4.10-rt4:
> > > > > >
> > > > > >   - Dick Hollenbeck reported that the printk rework had a
> > > > > > negative impact on the 8250 driver if not used as a console.
> > > > > > Patch by John Ogness.
> > > > > >
> > > > > > Known issues
> > > > > >      - None
> > > > > >
> > > > > > The delta patch against v5.4.10-rt4 is appended below and can
> > > > > > be found here:
> > > > > >
> > > > > >
> > > > > > https://cdn.kernel.org/pub/linux/kernel/projects/rt/5.4/incr/p
> > > > > >atch -5.4 .10-rt4-rt5.patch.xz
> > > > > >
> > > > > > You can get this release via the git tree at:
> > > > > >
> > > > > >
> > > > > > git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-deve
> > > > > >l.gi t v5.4.10-rt5
> > > > >
> > > > > I grabbed a copy of this, then turned off anything not needed to
> > > > > run LinuxCNC on an rpi4 in armhf config.  Then I noted its make
> > > > > had a make deb-pkg option.  But it isn't making what I told it
> > > > > to make as I'm sitting here watching it ALL go by. Did I miss
> > > > > something in  a make menuconfig that triggered a make all? It
> > > > > was supposedly set for armhf. But I'm even seeing x86 stuff go
> > > > > by. Obviously I know just enough to screw it up. Point me at the
> > > > > right docs for arm builds please.
> > > > >
> > > > > Hi Gene,
> > > >
> > > > I recently stumbled into deb-pkg, and it's awesome building up the
> > > > source and standard debian packages all in one command, but it
> > > > takes the same arguments as a standard make. For rpi4 this is
> > > > arm64 not armhf so you probably want something like below to
> > > > configure for arm64
> > >
> > > armhf (32 bit) runs fine in on an RPI4, been doing it for a couple
> > > months now. With a 32 bit stack frame, context switch latencies are
> > > several microseconds better which linuxcnc loves. However with mesa
> > > interface cards handling all the sub-millisecond stuffs and using
> > > preempt-rt running in userspace, it all works quite well as the  max
> > > latency stays below 200 microseconds 99.99% of the time. Thats well
> > > within the servo-thread time of 1 millisecond the mesa cards need.
> >
> > Ah, makes sense.
> >
> > > > If you are doing this on the rpi4 you don't need the
> > > > CROSS_COMPILE= option.[1][2] make -j4 ARCH=arm64
> > > > CROSS_COMPILE=aarch64-elf- defconfig
> > > > Or if the kernel you're already running has a /proc/config.gz you
> > > > can use that directly (zcat /proc/config.gz > .config).
> > > > Then you can use the main make.
> > >
> > > The kernel I an running was built, by me (queue the raspberry
> > > noises), with only the ondemand governer so while its working, its
> > > stuck in low gear. And the pi has plenty of cooling.
> > >
> > > that kernel running now is a 4.19.71-rt24-v7l+ #1 SMP PREEMPT RT,
> > > but there has since been added another video speedup option, so ATM
> > > I am trying to build a 4.19.94-rt38 announced last week. But the git
> > > clone I pulled doesn't have the rt patch. And pulling that patch
> > > with curl today fails:
> > >
> > > pi@rpi4:/media/pi/workspace $ curl
> > > http://www.kernel.org/pub/linux/kernel/projects/rt/4.19/patch-4.19.9
> > >4-rt38.patch.xz
> >
> > Hmm, this seems fine for me:
> >  wget
> > https://cdn.kernel.org/pub/linux/kernel/v4.x/linux-4.19.94.tar.xz
> > tar xf linux-4.19.94.tar.xz
> > cd linux-4.19.94/
> >  wget
> > http://www.kernel.org/pub/linux/kernel/projects/rt/4.19/patch-4.19.94-
> >rt38.patch.xz
> > unxz patch-4.19.94-rt38.patch.xz
> > patch -p1 < patch-4.19.94-rt38.patch
> I blew away my git clone and followed this, which all worked to here,
> but:
> >  make ARCH=armhf defconfig
Sorry that was a cut/paste typo, there is no arch/armhf just arm, so you want
make ARCH=arm defconfig
I had tried the command that's why it was in my history and thus the
copy/paste mistake. I believe how this works is the kernel just has
CONFIG_AEABI=y as the ABI config, then userspace compilers have to
decide if they want to compile for a hardware floating point or not,
and what debian has decided is that they would have a special
architecture just for hardfloat:
https://wiki.debian.org/ArmHardFloatPort

thanks,
Paul