How to build real-time kernel for Apalis IMX6

druzicka · January 5, 2016, 1:08pm

hi all,

has anybody tried to build real-time kernel for Apalis or Colibri IMX6 module with Yocto or OE?

i’ve tried to apply RT patch on kernel 3.14.28 (the one which OE builds with meta-toradex layer), but this failed. i know, it was a bit naive, but i tried that anyway.

thanks a lot,

david

max.tx · January 5, 2016, 4:32pm

Hello David

While this is not directly supported by Toradex one can apply the real-time patches to our i.MX6 Kernel.
In the meta-fsl-arm layer there is a recipe that applies the patches to the vanilla Freescale/NXP kernel tree. This includes addtional i.MX6 specific patches not included in the kernel.org real-time patch set.

github.com

Freescale/meta-fsl-arm/blob/fido/recipes-kernel/linux/linux-imx-rt_3.14.28.bb

# Adapted from linux-imx_3.14.28.bb

SUMMARY = "Linux real-time kernel based on linux-imx"
DESCRIPTION = "Linux kernel that is based on Freescale's linux-imx, \
with added real-time capabilities."

require recipes-kernel/linux/linux-imx.inc
require recipes-kernel/linux/linux-dtb.inc

DEPENDS += "lzop-native bc-native"

SRCBRANCH = "imx_3.14.28_1.0.0_ga"
SRCREV = "91cf351a2afc17ac4a260e4d2ad1e32d00925a1b"
LOCALVERSION = "-1.0.0_ga"

SRC_URI += "\
    file://0001-ARM-imx6q-drop-unnecessary-semicolon.patch \
    file://0002-ARM-clk-imx6q-fix-video-divider-for-rev-T0-1.0.patch \
    file://0003-ARM-imx6sl-Disable-imx6sl-specific-code-when-imx6sl-.patch \
    file://0004-mmc-sdhci-esdhc-imx-Fixup-runtime-PM-conditions-duri.patch \

This file has been truncated. show original

As Toradex did backport the extcon subsystem for use with the unusual USB client/host switching on the Colibri i.MX6 the real-time patch itself fails in two hunks. Thus one has to patch the patch before applying it to the kernel tree.

To build the real-time kernel outside of OE one can follow:

Before the configuring and building steps one would patch the kernel tree.

First download and unzip the real time patch from kernel.org. Then apply the patch for rt-patch to it.

Secondly apply the patches given in the linux-imx-rt_3.14.28.bb recipe in the order given in the SRC_URI variable.

Third configure the Kernel for the wanted module and then change the configuration using whatever is needed for your real-time use case.

Then build and deploy the kernel as one would normally do

One could also put together a recipe similar to linux-imx-rt, doing the patching of the patchfile before the do_patch task and thus automating the above steps.

Max

brandon.tx · January 6, 2016, 1:03am

As @max.krummenacher has already mentioned, we don’t officially support a real-time iMX6 kernel. However, we have one built & available for testing. Our real-time kernel is based on the linux-imx-rt_3.14.28 recipe from meta-fsl-arm. The steps to testing it are:

Download additional repo entries to the package manager:

wget –P /etc/opkg/ http://feeds.toradex.com/extra-kernel/2.5/conf/all/extra-kernel.conf
Update the package manager’s package cache:

opkg update
Download and execute an installation script to install and configure the real-time kernel:

cd

wget http://feeds.toradex.com/extra-kernel/2.5/conf/colibri-imx6/install-rt-kernel.sh

./install-rt-kernel.sh
Reset the system

reboot

The system should now boot the newly installed real-time kernel. Please refer to Max’s post for the details of how to build the kernel.

druzicka · January 7, 2016, 2:53pm

hi max,

thank you very much.

i’ve did what you suggested, ie. i’ve used the provided patch to patch RT patch (patch-3.14.28-rt25.patch) and let OE to patch the kernel from “meta-toradex” layer. i’m able to build 3.14.28-rt25 kernel now.

i’ve also included “rt-tools” into image. so, i can use “cyclictest” for initial tests, which already show some difference between RT and non-RT kernel.

thanks a lot guys.

david

druzicka · January 7, 2016, 2:56pm

hi brandon,

thanks for help. nevertheless, i can build rt kernel mine-self.

but this can be a great help for others.

dave