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Introduction
Creating Local Branch
Building Kernel
Rtver Utility
Cyclic Test
Running Utilities & Checking Results

You are here: Documentation » Altera SoC LTSI Kernel with Preempt-RT

Altera SoC LTSI Kernel with Preempt-RT

24 March 2015 - 22:25 | | Version 15 | VinceBridgers

Introduction

This page describes how to clone the LTSI Kernel v3.10 with Preempt-RT and test it to prove it works fine.

Creating Local Branch

Clone Rocketboards repo into a working directory named rocketboards. This could take some time. “rocketboards” could be any directory name you’d like.

git clone http://git.rocketboards.org/linux-socfpga.git rocketboards

CD into the directory created.cd rocketboards

Add a remote. I just happened to call this remote the same as the directory name, but it could be anything you’d like.

git remote add rocketboards http://git.rocketboards.org/linux-socfpga.git

List branches available from the remote. Note that the socfpga-3.10-ltsi-rt branch is bold, red and italicized.

$ git remote show rocketboards
* remote rocketboards
  Fetch URL: http://git.rocketboards.org/linux-socfpga.git
  Push  URL: http://git.rocketboards.org/linux-socfpga.git
  HEAD branch: master
  Remote branches:
    master               new (next fetch will store in remotes/rocketboards)
    socfpga-3.10         new (next fetch will store in remotes/rocketboards)
    socfpga-3.10-ltsi    new (next fetch will store in remotes/rocketboards)
    socfpga-3.10-ltsi-rt new (next fetch will store in remotes/rocketboards)
    socfpga-3.11         new (next fetch will store in remotes/rocketboards)
    socfpga-3.12         new (next fetch will store in remotes/rocketboards)
    socfpga-3.13         new (next fetch will store in remotes/rocketboards)
    socfpga-3.14         new (next fetch will store in remotes/rocketboards)
    socfpga-3.4-ltsi     new (next fetch will store in remotes/rocketboards)
    socfpga-3.6          new (next fetch will store in remotes/rocketboards)
    socfpga-3.7          new (next fetch will store in remotes/rocketboards)
    socfpga-3.7-ghrd     new (next fetch will store in remotes/rocketboards)
    socfpga-3.8          new (next fetch will store in remotes/rocketboards)
    socfpga-3.9          new (next fetch will store in remotes/rocketboards)
    socfpga-3.9-rel      new (next fetch will store in remotes/rocketboards)
    socfpga-3.9-rel-amp  new (next fetch will store in remotes/rocketboards)
  Local ref configured for 'git push':
    master pushes to master (up to date)

Fetch the remote. This fetches all remote references for a subsequent checkout. It’s necessary to fetch occasionally (once every 1-2 weeks) and rebase to pick up new changes that are available as they are pushed out to Rocketboards for customers.

$ git fetch rocketboards
From http://git.rocketboards.org/linux-socfpga
* [new branch]      master     → rocketboards/master
* [new branch]      socfpga-3.10 → rocketboards/socfpga-3.10
* [new branch]      socfpga-3.10-ltsi → rocketboards/socfpga-3.10-ltsi
* [new branch]      socfpga-3.10-ltsi-rt → rocketboards/socfpga-3.10-ltsi-rt
* [new branch]      socfpga-3.11 → rocketboards/socfpga-3.11
* [new branch]      socfpga-3.12 → rocketboards/socfpga-3.12
* [new branch]      socfpga-3.13 → rocketboards/socfpga-3.13
* [new branch]      socfpga-3.14 → rocketboards/socfpga-3.14
* [new branch]      socfpga-3.4-ltsi → rocketboards/socfpga-3.4-ltsi
* [new branch]      socfpga-3.6 → rocketboards/socfpga-3.6
* [new branch]      socfpga-3.7 → rocketboards/socfpga-3.7
* [new branch]      socfpga-3.7-ghrd → rocketboards/socfpga-3.7-ghrd
* [new branch]      socfpga-3.8 → rocketboards/socfpga-3.8
* [new branch]      socfpga-3.9 → rocketboards/socfpga-3.9
* [new branch]      socfpga-3.9-rel → rocketboards/socfpga-3.9-rel
* [new branch]      socfpga-3.9-rel-amp → rocketboards/socfpga-3.9-rel-amp

Checkout the Linux-RT branch. Note that this command creates a local branch named “linux-rt”. This name could be anything you’d like it to be. rocketboards/socfpga-3.10-ltsi-rt is the /referenced above.

$ git checkout -b linux-rt rocketboards/socfpga-3.10-ltsi-rt
Checking out files: 100% (26318/26318), done.
Branch linux-rt set up to track remote branch socfpga-3.10-ltsi-rt from rocketboards.
Switched to a new branch 'linux-rt'

Building Kernel

Assuming tools and such are installed, build the kernel normally.

make socfpga_defconfig
make -j12 zImage 2>&1 | tee ../linux-rt-log.txt

Rtver Utility

Save the following source code to a file and compile using g++. This will be referred to as the rtver utility.

#include <string.h>
#include <stdio.h>
#include <sys/utsname.h>

int main(int argc, char **argv)
{
        struct utsname u;
        int crit2=0;
        char *substr;
        FILE *fd;

        uname(&u);
        substr = strcasestr(u.version, "PREEMPT RT");
        if ((fd = fopen("/sys/kernel/realtime","r")) != NULL) {
                int flag;
                crit2 = ((fscanf(fd, "%d", &flag) == 1) && (flag==1));
                fclose(fd);
        }
        fprintf(stderr, "this is a %s kernel\n",
                (substr && crit2) ? "PREEMPT RT" : "vanilla");

}

Cyclic Test

Clone and build the cyclic test utility as described at https://rt.wiki.kernel.org/index.php/Cyclictest

Running Utilities & Checking Results

Preempt-Enabled Kernel Results

root@socfpga_cyclone5:~# ./rtver
this is a PREEMPT RT kernel

root@socfpga_cyclone5:~# ./cyclictest --duration=20 -t8 -p80 -m --policy=rr -a1
# /dev/cpu_dma_latency set to 0us
policy: fifo: loadavg: 0.03 0.01 0.01 1/65 194

T: 0 (  187) P:80 I:1000 C:  19501 Min:     26 Act:   28 Avg:   29 Max:      98
T: 1 (  188) P:80 I:1500 C:  13001 Min:     26 Act:   35 Avg:   29 Max:     144
T: 2 (  189) P:80 I:2000 C:   9737 Min:     26 Act:   27 Avg:   29 Max:      96
T: 3 (  190) P:80 I:2500 C:   7789 Min:     25 Act:   27 Avg:   31 Max:     128
T: 4 (  191) P:80 I:3000 C:   6649 Min:     26 Act:   31 Avg:   37 Max:     118
T: 5 (  192) P:80 I:3500 C:   5691 Min:     26 Act:   34 Avg:   29 Max:     105
T: 6 (  193) P:80 I:4000 C:   4972 Min:     26 Act:   36 Avg:   43 Max:     123
T: 7 (  194) P:80 I:4500 C:   4413 Min:     26 Act:   38 Avg:   29 Max:      96