update to latest v5.4-rt kernel for sam9x35 SOC

[yosi yarchi]

Hi


Thank you for your detailed response


could you provide some clarifications for the following issues?

1. is update process is the same, if I want to upgrade to highest 
kernel-rt version? if so, do I limited to 5.15.96 (highest linux4sam 
kernel is linux-5.15-mchp/105. highest stable rt kernel is linux-5.15.96)?

2. when do you plan to release new kernel-rt?

3. what is the purpose of 
git://git.kernel.org/pub/scm/linux/kernel/git/at91/linux.git repository?


With best regards

Yosi Yarchi




On 4/5/23 19:42, Nicolas.Ferre at microchip.com wrote:
> Yosi Yarchi,
>
> On 04/04/2023 at 17:55, yosi yarchi wrote:
>>      Hi
>>
>>        I'm working currently with 5.4.41-linux4sam-2020.04-rt kernel on
>>        sam9x35 SOC. there are no updates for this kernel for long time
>>        (since 2020).
> Yes, in the meantime, we switched our "vendor kernel" to newer kernel
> revisions and continued our work to mainline the out-of-tree changes.
>
> For this particular SoC, I would say that all needed pieces are in
> Mainline for a long time, so I would always advise to go with the latest
> upstream kernel (with RT_PREEMPT extension in this case).
> That being said, I admit that you want to stick with 5.4.x kernels for
> various reasons.
>
>>        at linux-stable-rt, however, there are lot of
>>        updates for v5.4 kernel. I want to update to latest v5.4 kernel. I
>>        thought to:
>>
>>          1. take linux-stable-rt repository as my base
>>          2. add missing files from maintainers repository
>> git://git.kernel.org/pub/scm/linux/kernel/git/at91/linux.git
>>            repository (pointed by MAINTAINERS file).
>>
>>          however, what about exist but less updated files? the file
>>            drivers/dma/at_hdmac.c, for example, exist at both
>>            repositories, but git log shows that there are much more
>>            updates at maintainers repository than to linux-stable-rt
>>            repository (even at specific date, Oct 25 2022, for example).
>>
>>       my question is: what is the right way to update to latest 5.4-rt
>>        kernel on sam9x SOCs?
> I would take the reverse approach as it's what we do for building our
> Linux4SAM/Linux4Microchip kernels:
>
> 1/ start with non-rt latest version of linux4sam 5.4: branch
> linux-5.4-at91 that has the stable updates up to v5.4.104 (March 2021)
> 2/ little by little (chunk of 10 revisions), merge upstream stable
> kernels, fix merge conflicts, continue, iterate, up to v5.4.230 (see below)
> 3/ during this process, test regularly the resulting kernel on your
> system or even better in a CI loop to automate the process
> 4/ stop when you've reached the more recent 5.4 stable kernel *with rt
> extensions* (5.4.230 as I can see on
> https://mirrors.edge.kernel.org/pub/linux/kernel/projects/rt/5.4/)
> 5/ now you can merge v5.4.230-rt80 on your updated kernel. If you find
> conflicts or difficulties, take the v5.4.41-rt kernel as an example of
> how to solve the conflicts for sam9x35. The most challenging part must
> be related to timers: see how it's done for the kernel you use now
> (v5.4.41-rt) to replicate this on the newer kernel if needed.
>
> In any case, don't hesitate to fill-in a support ticket with Microchip
> to address this special case.
>
> Hope that it helps. Best regards,
>     Nicolas
>