Raspberry Pi 4

Hello & Thanks

Trying your RT with linuxcnc was on my To Do list.Now near the top! I will try it out over the next day or two.

I'm currently using Picnc & Jessie 4.4.4RT Both of which are sliding into bitrot. Having said that they do work very well for my use case. The Pi4 + Mesa 7c8x solution looks a very attractive replacement if the Picnc cannot be revived and updated.
I don't think Guysoft set out to do anything more than make and publish an RT based on the Raspbian stock kernel.

I'm still in the exploration phase ATM. So trying stuff as it evolves.

Any further comments - suggestions on optimisation of the otherwise stock Buster RT would be appreciated.

Thanks for sharing and publishing you work.
I'm sure I will be back to ask more questions

Cheers
MrGreg

MrGreg wrote:

Hello & Thanks

Trying your RT with linuxcnc was on my To Do list.Now near the top! I will try it out over the next day or two.

I'm currently using Picnc & Jessie 4.4.4RT Both of which are sliding into bitrot. Having said that they do work very well for my use case. The Pi4 + Mesa 7c8x solution looks a very attractive replacement if the Picnc cannot be revived and updated.
I don't think Guysoft set out to do anything more than make and publish an RT based on the Raspbian stock kernel.

I'm still in the exploration phase ATM. So trying stuff as it evolves.

Any further comments - suggestions on optimisation of the otherwise stock Buster RT would be appreciated.

Thanks for sharing and publishing you work.
I'm sure I will be back to ask more questions
=====
This kernel supports the new, about 20x faster video modes, just select it in raspi-config after the upgrade has been done. 60 fps from glxgears at full screen.

Due to missing dependencies, gscreen is not supported, but axis with pyvcp gingerbread for a gui works great.

Cheers
MrGreg

Hello Gene

Tried the self installing RT, initially on a Pi3 and then on a Pi4. on a new 32GB SD ( don't have a 64 )

The extract failed ( due to problems of previous errors? it said) There was a massive amount of output so I could not scroll back far enough to identify what the errors were.
Guess it is possible I have a corrupted file? Do you have a sha or md I can check with?

Cheers
MrGreg

MrGreg wrote:

Hello Gene

Tried the self installing RT, initially on a Pi3 and then on a Pi4. on a new 32GB SD ( don't have a 64 )

The extract failed ( due to problems of previous errors? it said) There was a massive amount of output so I could not scroll back far enough to identify what the errors were.
Guess it is possible I have a corrupted file? Do you have a sha or md I can check with?

Cheers
MrGreg

You can add to the shells history from one of its pull-downs, 10k ought to be enough.
sha512sum is of rt-kernel.tgz is

7a8c62a171bd2a24f87635dd0b910a49acc9b99e0878698fabbab57b2f9aebd771911851599dd84e44eec55a973b5d02075eb0a4379136a868d09fa991638ded

I hope this helps

Hello again

The sha is good.
Hitting a permissions issue:
Lots of......
boot/bcm2708-rpi-b.dtb
tar: boot/bcm2708-rpi-b.dtb: Cannot change ownership to uid 1000, gid 1000: Operation not permitted
boot/bcm2708-rpi-b-plus.dtb

Did a chmod 755 on it but still get the same extraction error even when root@
???

Cheers
MrGreg

MrGreg wrote:

Hello again

The sha is good.
Hitting a permissions issue:
Lots of......
boot/bcm2708-rpi-b.dtb
tar: boot/bcm2708-rpi-b.dtb: Cannot change ownership to uid 1000, gid 1000: Operation not permitted
boot/bcm2708-rpi-b-plus.dtb

Did a chmod 755 on it but still get the same extraction error even when root@
???

Cheers
MrGreg

My install was from the big image, done by a root session of mc. So everything in /boot is marked root:root.
boot itself as we see it, is a fat32 filesystem hiding behind an ext4 directory structure. And the fat32 has no facility for changing ownerships. So while its not jack sh-- to the pi, ownership is moot. So while it was all built here as the user pi, let me try something, as in making the unpacked tree, there are 2 in that tgz, /boot/, and /lib/ all owned by root, and regenerate the .tgz.

I had zero such problems installing it from the 2.5Gig archive. All of which was built by the user pi, so its all owned by pi. So, will it unpack if placed in /tmp?
if so, then you might try "sudo chown -R root:root boot" and repeat for lib.. If that works then cd boot;
sudo cp -rd * /boot/
cd ../lib
sudo cp -dr * /lib/
cd ../overlays
sudo cp -d * /boot/overlays/
cd ..
sudo cp -d bcm* /boot/

add the following entry to /boot/config.txt useing nano as root:
cd /boot
nano config.txt and add:
kernel=kernel7i-rt.img

ctrl+x,y to save and exit nano

This last isn't done by my package, I'd forgotten that detail. I'll put that in the README

Now you should be able to reboot the pi,, and a uname -a should print something like:
Linux rpi4.coyote.den 4.19.71-rt24-v7l+ #1 SMP PREEMPT RT Thu Feb 6 07:09:18 EST 2020 armv7l GNU/Linux

Let me know if this fails. In the meantime I'll see if I can fix the .tgz and rebuild it.

Hello again

This on Pi3, Pi4 is busy atm
I sort of jumped the gun a bit...

I extracted locally and copied / overwrote contents to boot & lib (modules) back in to RFS
Also checked out config.txt and put ( the only rt obviously available)
kernel=kernel7i-rt.img
(As the orig 4.19.9x was still the default boot)
It booted up OK with the 4.19.71RT reported by uname -a

Re ran the rt-tests with
cyclictest -n -p 90 -i 1000

Rather disappointing results. Got latency of circa 480uS after heavy loading of over 30 mins or so.

I will wipe, start over and re run according to your suggestion/instruction Might well be missing some of the optimisation detail given my quick and dirty kludge ?

Cheers & thanks
MrGreg

MrGreg wrote:

Hello again

This on Pi3, Pi4 is busy atm
I sort of jumped the gun a bit...

I extracted locally and copied / overwrote contents to boot & lib (modules) back in to RFS
Also checked out config.txt and put ( the only rt obviously available)
kernel=kernel7i-rt.img
(As the orig 4.19.9x was still the default boot)
It booted up OK with the 4.19.71RT reported by uname -a

Re ran the rt-tests with
cyclictest -n -p 90 -i 1000

Where do I get that? I use latency-test from the linuxcnc package. And lightly loaded on an rpi4, I am getting less than 10 u-secs.

Rather disappointing results. Got latency of circa 480uS after heavy loading of over 30 mins or so.

I will wipe, start over and re run according to your suggestion/instruction Might well be missing some of the optimisation detail given my quick and dirty kludge ?

Cheers & thanks
MrGreg

Did you run raspi-config and enable the new video? I think it lowers latency even on the pi3. But this kernel is built for a pi4, not a pi3, which I've not tried with this kernel.

Take care now, MrGreg

Gene heelo
I downloaded the kernel img...
oops it changed again on 22 feb so my original thought is not up-to-date

anyway
I think you should supply the config.txt and cmdline.txt
so other users can duplicate your setup.
Because I already got the previous incarnattion (~4days ago )
and supplied what i thought were like your config.txt cmdline.txt
( which wsa isolcpus-3, no mention of idle=poll ..
thats as close as i can guess from your posts ..)
and got > 54uS right away, 4 tests,
no time to add any other processes for extra load,
and 4 cold boot retires)
so, i think there is something missing,
something outide of geneslinuxbox.net:6309/gene/lathe-stf/li...c4pi4b/rt-kernel.tgz
May be you have a low rez monitor? mine is 1380x??? not on rpinow ;-9

I appreciate your work, i just dont get the expected results.
thx
tomp

Hello,
I also used PiCNC on an rpi3b.
What problems do you find using it for rpi4/buster?

Its a great idea but the SPI is limited to thread speed
so its like the speed issues of the parallel port.

thx
tomp