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ChrisK

RT patches for sun8i kernel?

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I can't help you when you use buildroot ... you are adding unnecessary complexity to the problem and on the end, you will be disappointed on the RT performance with the old legacy kernel. Go for new 4.13 kernel, add appropriate RT patch to userpatches/kernel/sunxi-next/ recompile kernel and install .deb packages. Can't be more simple than this.

 

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Hi all,

 

Just wanted to share that I got the realtime patch working on an Orange Pi Zero on 4.18.8

I used the armbian build environment and the official RT patch.

 

A few tricky points were the CPU govenor and CPU operating points automatically switching by default, causing the realtime behavior to be really bad (max spikes around 3000 in cpu test).

By patching the device tree to only use a fixed operating point, I achieve the following output:

Linux orangepizero 4.14.8-rt9-sunxi #1 SMP PREEMPT RT Sat Jan 6 14:36:31 CET 2018 armv7l armv7l armv7l GNU/Linux
/root/rt-tests/cyclictest -p 80 -t5 –n
# /dev/cpu_dma_latency set to 0us
policy: fifo: loadavg: 0.85 0.49 0.22 4/168 3083

T: 0 ( 3079) P:80 I:1000 C:   3297 Min:      8 Act:   17 Avg:   16 Max:      66
T: 1 ( 3080) P:80 I:1500 C:   2198 Min:      8 Act:   24 Avg:   15 Max:      50
T: 2 ( 3081) P:80 I:2000 C:   1648 Min:      8 Act:   11 Avg:   16 Max:      60
T: 3 ( 3082) P:80 I:2500 C:   1318 Min:      8 Act:   12 Avg:   15 Max:      44
T: 4 ( 3083) P:80 I:3000 C:   1098 Min:      9 Act:   17 Avg:   18 Max:      57

 

If anyone is interested, I used this realtime kernel to run a virtual wifi guitar amplifier on the orange pi zero.

I documented the entire thing on http://arre234.blogspot.be/2018/02/linux-portable-wifi-guitar-amp-on.html , including the device tree and cpu govenor stuff.

 

Hope this helps anyone

 

Arnout

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