Re: [yocto] [meta-raspberrypi] Is Preempt-rt still supported in master / latest releases?

[Lukasz Majewski <lukma@denx.de>]

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Hi Carles

> Hi Alex, Andrei,
> 
> thanks for your reply. Based on your feedback I've tried the
> following:
> - I have downloaded the patch patch-5.15.86-rt56.patch from
> https://cdn.kernel.org/pub/linux/kernel/projects/rt/5.15/ and stored
> in ./meta-raspberrypi/recipes-kernel/linux/files
> - I have created a file linux-raspberrypi_%.bbappend in
> ./meta-raspberrypi/recipes-kernel/linux
> - I have created a .cfg file with CONFIG_PREEMPT_RT_FULL = y in
> ./meta-raspberrypi/recipes-kernel/linux/files
> - I have added both patch and cfg file in bbappend using
> SRC_URI:append:rpi.
> 
> I can observe the following:
> - patch and cfg files are available in
> ./build/tmp/work/raspberrypi4_64-agl-linux/linux-raspberrypi/1_5.15.34+gitAUTOINC+e1b976ee4f_0086da6acd-r0
> - new folder linux-raspberrypi4_64-preempt-rt-build is available
> inside the folder above. But the problem seems to be that
> CONFIG_PREEMPT_RT = y is not applied to the .config file. So it seems
> the preempt-rt kernel is built but without the full preempt-rt
> support.
> - When I do bitbake linux-raspberrypi -c menuconfig I cannot select
> the full real time preempt kernel, only preemptible option available
> is --> Preemptible Kernel (Low-Latency Desktop). Fully Preemptible
> Kernel (Real-Time) is not available.
> - When I flash the image in the Rpi4 and run uname -r I see that the
> rt kernel has been built --> 5.15.34.rt56.v8
> - but only with PREEMPT option but without RT when I do uname -v -->
> #1 SMP PREEMPT Tue Aug 9 21:20:00 UTC 2022 (without RT).
> 
> I have tried building linux-yocto-rt for qemu and there I see that
> CONFIG_PREEMP_RT = y is available in the .config file. Also if I open
> menuconfig I have the option to select in General setup -->
> Preemption Model --> Fully Preemptible Kernel (Real-Time)
> 
> If you can provide any hints on what am I missing it would be highly
> appreciated.
> 

Have you managed to go any further with your investigation regarding
PREEMPT-RT on RPi4-64?

> Best Regards,
> Carles




Best regards,

Lukasz Majewski

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