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Real Time (RT) Linux Kernel for AM64x_EVM and kernel version

Dominic Rath
Mastermind 7620 points
Part Number: PROCESSOR-SDK-AM64X


Dear TI team,

we've started working with a AM64x_EVM board.

I've got the PROCESSOR-SDK-AM64X-LINUX and the PROCESSOR-SDK-AM64X, unfortunately I couldn't find a RT kernel in either of the two.

The release notes mention an RT kernel: https://software-dl.ti.com/processor-sdk-sitara/esd/am64x/latest/exports/docs/devices/AM64X/Linux_Release_Notes.html

I'm not 100% if the information from the release notes is correct though, since the version numbers don't match:

root@am64xx-evm:~# uname -a

Linux am64xx-evm 5.4.91-g1af1264b70 #1 SMP PREEMPT Thu Jan 28 20:42:53 UTC 2021 aarch64 GNU/Linux

The release notes say the kernel ought to be version 5.4.87:

I'm also slightly worried since the Repo listed for both the normal Linux Kernel and the RT kernel refer to a TI-internal git server, not to the public git.ti.com server.

  • Is there a RT kernel for the AM64x_EVM available?
  • Is there updated build information available for the kernel actually shipped with the Linux SDK?
  • Does AM64x_EVM support require patches that are only available on the TI internal Git, or is all of this support already available on the public server?

Regards,

Dominic

  • 0
    TI__Guru**** 174071 points

    Hi Dominic,

    The RT Linux for AM64x will be included in future SDK releases.

    Sorry for the documentation error about the git repo. The public mirror is git://git.ti.com/ti-linux-kernel/ti-linux-kernel.git. The rest of the information in the documentation including the HEAD commit and the release tag are all correct.

    I will ask our dev team why the prebuilt kernel image signature doesn't match with the release notes and get you back.

  • 0
    TI__Guru**** 174071 points

    Hi Dominic,

    Dominic Rath said:
    I'm not 100% if the information from the release notes is correct though, since the version numbers don't match:

    The Linux kernel in this Processor SDK v7.02 release has one more patch on top of the information in the Release Notes - the patch disables the ADC in board DTS for Linux, because the ADC is used by R5F for the Benchmark demo.

  • 0 in reply to Bin Liu
    Mastermind 7620 points

    Hi Bin,

    Bin Liu said:
    The Linux kernel in this Processor SDK v7.02 release has one more patch on top of the information in the Release Notes - the patch disables the ADC in board DTS for Linux, because the ADC is used by R5F for the Benchmark demo.

    I believe there's still something missing.

    If I check out the commit listed in the relase notes I end up with a tree that is apparently 5.4.87 (e.g. the top level Makefile says SUBLEVEL = 87) and that contains a considerable amount of differences compared to the linux-5.4.91+gitAUTOINC+4f9a563c39-g1af1264b70 tree that comes with the installer.

    Since the prebuilt kernel says it is 5.4.91, too, I'm guessing that this is indeed the correct version.

    It seems that commit 4f9a563c39fa95af40d8f3119a64c347cbca3b45 was used as the base for the Linux kernel released with SDK 07.02 for the AM64x. The only difference between that commit and linux-5.4.91+gitAUTOINC+4f9a563c39-g1af1264b70 is a change to the DTS that disables ADC, like you said.

    Bin Liu said:
    The RT Linux for AM64x will be included in future SDK releases.

    "future SDK releases" sounds very vague - do you have any idea which SDK release and when this RT support is supposed to be included?

    Are there any known issues with the current state of the RT kernel?

    Regards,

    Dominic

  • 0 in reply to Dominic Rath
    TI__Guru**** 174071 points

    Hi Dominic,

    I think you are right, the kernel prebuilt and source code packaged in the Processor SDK v7.2 release are not aligned with the Release Notes. It seems the SDK has taken the HEAD of ti-linux-5.4.y branch (which has kernel v5.4.91 merged at the time of packaging) then added the ADC DTS change, not the release tag 07.02.00.004. I will confirm this internally.

    Dominic Rath said:
    "future SDK releases" sounds very vague - do you have any idea which SDK release and when this RT support is supposed to be included?

    The next release is scheduled at the end of March. I will confirm if RT kernel will be included in the next release.

    Dominic Rath said:
    Are there any known issues with the current state of the RT kernel?

    All the known issues are listed in the Release Notes of the Processor SDK v7.2.

  • 0 in reply to Bin Liu
    TI__Guru**** 174071 points

    Bin Liu said:
    Dominic Rath
    "future SDK releases" sounds very vague - do you have any idea which SDK release and when this RT support is supposed to be included?

    The next release is scheduled at the end of March. I will confirm if RT kernel will be included in the next release.

    RT Linux will be provided in the coming SDK release in March.