Voir la source de Raspberry Pi rt-kernel

Compiler/tester un noyau temps-réel audio sur raspberry pi2

=Test de latence du noyau=

*Setup : raspi2 + qjackctl 0.3.9 + sooperlooper 1.6.18 + carte son xenyx 302USB behringer
 
==Outils de test==

===Connaitre les réglages actuel du noyau===
 zcat /proc/config.gz > ~/config
si il n'y à pas de fichier de configuration
 sudo modprobe configs

===RealTimeConfigQuickScan===
scripts qui permettent de connaitre la configuration du kernel
 git clone git://github.com/raboof/realtimeconfigquickscan.git
 cd realtimeconfigquickscan
 perl ./realTimeConfigQuickScan.pl

===Cyclictest===
Tester les performances temps réel 

 git clone git://git.kernel.org/pub/scm/linux/kernel/git/clrkwllms/rt-tests.git 
 cd rt-tests
 make all
 sudo cp ./cyclictest /usr/bin/
 cd ~
 sudo cyclictest -l1000000 -m -n -a0 -t1 -p99 -i400 -h400 -q
ou tester chaque coeurs
 sudo cyclictest -a -t -n -p99
Les résultats sont en microsecondes

*source
https://www.osadl.org/Realtime-Preempt-Kernel.kernel-rt.0.html#externaltestingtool<br />
https://github.com/raboof/realtimeconfigquickscan<br />
http://www.linuxtopia.org/online_books/linux_kernel/kernel_configuration/ch08.html<br />
https://rt.wiki.kernel.org/index.php/Cyclictest<br />
http://people.redhat.com/williams/latency-howto/rt-latency-howto.txt<br />

==CCRMA Satellite pi2==
https://ccrma.stanford.edu/~eberdahl/Satellite/

===Installation/Configuration===
[https://ccrma.stanford.edu/~eberdahl/Satellite/ CCRMA Satellite] (une distribution créer pour faire de l'audio)
*copier l'image su la carte sd
 sudo dd if=/home/blablabla/SatelliteCCRMA_Rpi2_v1.03.dd of=/dev/mmcblk0 bs=4096
*login et mot de passe
 login : ccrma
 mp : temppwd
*arrêter les scripts par défaults
 exit-stand-alone
 sudo rm /etc/default/randomsound
 sudo rm /etc/init.d/randomsound
 sudo /home/ccrma/bin/disable-flash-writes
*relancer le système
 sudo reboot
*lancer x
 startx

===Alors quoi?===
*Pour le moment pd-extended crash régulièrement donc préférer la version vanilla...<br />
*qjackctl ne fonctionne qu'en root donc sooplerlooper aussi
*pas trop de documentation : https://groups.google.com/forum/#!topic/satelliteccrma/gAvRQd8XbHY

*test avec la carte son scarlett 2i2 : il faut modifier le fichier /boot/cmdline.txt et ajouter
 dwc_otg.fiq_fsm_enable=0 
[http://www.linuxmao.org/forumthread64929?forumId=2&comments_threshold=0&comments_parentId=64929&comments_offset=20&comments_per_page=20&thread_style=commentStyle_plain source]

*test avec behringer xenyx302USB
pas de soucis de latence avec jack jusqu'à 48KHz, 128 échantillons : 5.33ms

===Test de copie du kernel===
Le coté audio de cette distribution étant plutôt satisfaisant, mais la surcouche concernant la protection en écriture et les scripts inutiles donnent envie de récupérer le kernel sur une distribution plus basique.

 Copie de /boot/kernel7.img 
 Copie de /boot/bcm2709-rpi-2-b.dtb 
 Copie de cmdline.txt
 Copie de config.txt

 sudo apt-get install cpufrequtils
modifier rc.local
 cpufreq-set -g performance
 swapoff -a

sources:<br />
https://www.bentasker.co.uk/documentation/linux/304-copying-a-linux-kernel-from-one-system-to-another<br />
http://ubuntuforums.org/showthread.php?t=829472<br />
https://forums.gentoo.org/viewtopic-t-813106-start-0.html<br />
http://superuser.com/questions/439511/how-to-save-or-export-a-custom-linux-kernel-configuration<br />
http://superuser.com/questions/287371/obtain-kernel-config-from-currently-running-linux-system<br />

===proc/version===
 ccrma@satellite ~/Desktop/realtime $ cat /proc/version 
 Linux version 3.18.11-v7+ (dc4@dc4-XPS13-9333) (gcc version 4.8.3 20140303 (prerelease) (crosstool-NG linaro-1.13.1+bzr2650 - Linaro GCC 2014.03) ) #781 SMP PREEMPT Tue Apr 21 18:07:59 BST 2015


===CyclicTest===
Test avec SooperLooper 3 pistes, jack : 128 échantillons, 44100 Hz, 3 périodes/tampon

 ccrma@satellite ~ $ sudo cyclictest -a -t -n -p99
 # /dev/cpu_dma_latency set to 0us
 policy: fifo: loadavg: 0.78 0.45 0.24 4/220 4238          
 
 T: 0 ( 4079) P:99 I:1000 C: 348228 Min:     10 Act:   26 Avg:   22 Max:     749
 T: 1 ( 4080) P:99 I:1500 C: 232139 Min:      9 Act:   26 Avg:   19 Max:     205
 T: 2 ( 4081) P:99 I:2000 C: 174114 Min:      9 Act:   38 Avg:   18 Max:     153
 T: 3 ( 4082) P:99 I:2500 C: 139291 Min:      9 Act:   39 Avg:   20 Max:     717

===QuickScan===

 ccrma@satellite ~/Desktop/realtime $ perl ./realTimeConfigQuickScan.pl 
 == GUI-enabled checks ==
 Checking if you are root... no - good
 Checking filesystem 'noatime' parameter... 3.18.11 kernel - good
 (relatime is default since 2.6.30)
 Checking CPU Governors... CPU 0: 'performance' CPU 1: 'performance' CPU 2: 'performance' CPU 3: 'performance'  - good
 Checking swappiness... 1 - good
 Checking for resource-intensive background processes... none found - good
 Checking checking sysctl inotify max_user_watches... < 524288 - not good
 increase max_user_watches by adding 'fs.inotify.max_user_watches = 524288' to /etc/sysctl.conf and rebooting
 For more information, see http://wiki.linuxaudio.org/wiki/system_configuration#sysctlconf
 Checking access to the high precision event timer... not found - not good
 /dev/hpet not found.
 Checking access to the real-time clock... not found - not good
 /dev/rtc not found (perhaps create a symlink?).
 Checking whether you're in the 'audio' group... yes - good
 Checking for multiple 'audio' groups... no - good
 Checking the ability to prioritize processes with chrt... yes - good
 Checking kernel support for high resolution timers... found - good
 Kernel with Real-Time Preemption... not found - not good
 Kernel without real-time capabilities found
 For more information, see http://wiki.linuxaudio.org/wiki/system_configuration#installing_a_real-time_kernel
 Checking if kernel system timer is set to 1000 hz... not found - not good
 Try setting CONFIG_HZ to 1000 
 
 Checking kernel support for tickless timer... found - good
 == Other checks ==
 Checking filesystem types... ok.
 ok.
 ** Set $SOUND_CARD_IRQ to the IRQ of your soundcard to enable more checks.
    Find your sound card's IRQ by looking at '/proc/interrupts' and lspci.

==Raspbian wheezy pi2==
Version d'origine sans overclock

 pi@raspberrypi  cat /proc/version 
 Linux version 3.18.11-v7+ (dc4@dc4-XPS13-9333) (gcc version 4.8.3 20140303 (prerelease) (crosstool-NG linaro-1.13.1+bzr2650 - Linaro GCC 2014.03) ) #781 SMP PREEMPT Tue Apr 21 18:07:59 BST 2015

===CyclicTest===
Test avec SooperLooper 3 pistes, jack : 128 échantillons, 44100 Hz, 3 périodes/tampon<br />
SooperLooper : got Xrun après environ une minute de test

 pi@raspberrypi ~ $ sudo cyclictest -a -t -n -p99
 # /dev/cpu_dma_latency set to 0us
 policy: fifo: loadavg: 1.61 0.77 0.38 2/218 3923          
 
 T: 0 ( 3910) P:99 I:1000 C:  94273 Min:     15 Act:   24 Avg:   45 Max:     867
 T: 1 ( 3911) P:99 I:1500 C:  62852 Min:     17 Act:   26 Avg:   36 Max:     364
 T: 2 ( 3912) P:99 I:2000 C:  47139 Min:     15 Act:   18 Avg:   31 Max:     421
 T: 3 ( 3913) P:99 I:2500 C:  37711 Min:     15 Act:   29 Avg:   35 Max:     362

 pi@raspberrypi ~ $ sudo cyclictest -l1000000 -m -n -a0 -t1 -p99 -i400 -h400 -q
 # /dev/cpu_dma_latency set to 0us
 # Histogram
 
 # Total: 000249828
 # Min Latencies: 00014
 # Avg Latencies: 00036
 # Max Latencies: 00730
 # Histogram Overflows: 00088
 # Histogram Overflow at cycle number:
 # Thread 0: 09404 44073 44392 44551 44630 44869 44908 44988 44989 45025  225464 225760 226073 226682 227131 227653 228740 229146 229241 229244  229416 229797 229801 229893 229954 230007 230010 230071 230186 230275 230368 230467 230487 230545 230563 230680 230757 230916 231005 231099 231103 231195 231236 231332 231579 231713 232099 232959 233891 233892 234087 234464 234614 234621 236152 237379 237733 237818 237987 238038 238040 238078 238142 238236 238330 238474 238691 239425 239515 239608 239723 239726 240186 240189 240353 240467 241170 241259 241349 241539 241596 241630 241633 241724 241873 241907 241971 242005

===QuickScan===
 pi@raspberrypi ~/realtimeconfigquickscan $ perl ./realTimeConfigQuickScan.pl
 == GUI-enabled checks ==
 Checking if you are root... no - good
 Checking filesystem 'noatime' parameter... 3.18.11 kernel - good
 (relatime is default since 2.6.30)
 Checking CPU Governors... CPU 0: 'powersave' CPU 1: 'powersave' CPU 2: 'powersave' CPU 3: 'powersave'  - not good
 Set CPU Governors to 'performance' with 'cpufreq-set -c <cpunr> -g performance'
 See also: http://linuxmusicians.com/viewtopic.php?f=27&t=844
 Checking swappiness... 1 - good
 Checking for resource-intensive background processes... none found - good
 Checking checking sysctl inotify max_user_watches... < 524288 - not good
 increase max_user_watches by adding 'fs.inotify.max_user_watches = 524288' to /etc/sysctl.conf and rebooting
 For more information, see http://wiki.linuxaudio.org/wiki/system_configuration#sysctlconf
 Checking access to the high precision event timer... not found - not good
 /dev/hpet not found.
 Checking access to the real-time clock... not found - not good
 /dev/rtc not found (perhaps create a symlink?).
 Checking whether you're in the 'audio' group... yes - good
 Checking for multiple 'audio' groups... no - good
 Checking the ability to prioritize processes with chrt... yes - good
 Checking kernel support for high resolution timers... found - good
 Kernel with Real-Time Preemption... not found - not good
 Kernel without real-time capabilities found
 For more information, see http://wiki.linuxaudio.org/wiki/system_configuration#installing_a_real-time_kernel
 Checking if kernel system timer is set to 1000 hz... not found - not good
 Try setting CONFIG_HZ to 1000
 
 Checking kernel support for tickless timer... found - good
 == Other checks ==
 Checking filesystem types... ok.
 not found.
 ** Warning: no tmpfs partition mounted on /tmp
   For more information, see:
   - http://wiki.linuxaudio.org/wiki/system_configuration#tmpfs
   - http://lowlatency.linuxaudio.org
 ** Set $SOUND_CARD_IRQ to the IRQ of your soundcard to enable more checks.
   Find your sound card's IRQ by looking at '/proc/interrupts' and lspci.

==RaspbianWheezy + modifs ccrma pi2==

===Comparaison wheezy/ccrma===
Le /boot de la CCRMA-Satellite est identique à la Raspbian-Wheezy de base à part quelques modifications des fichiers cmdline.txt et config.txt et l'ajout de os_config.json.<br />
*/boot/cmdline.txt : En gras ce qui est ajouté sur la version CCRMA
 dwc_otg.lpm_enable=0 console=ttyAMA0,115200 console=tty1 root=/dev/mmcblk0p'''6''' rootfstype=ext4 elevator=deadline rootwait '''fastboot noswap cgroup_enable=memory'''

Pour comprendre les options de boot c'est par [https://github.com/raspberrypi/linux/blob/rpi-3.18.y/Documentation/kernel-parameters.txt là] 

*/etc/rc.local :il à aussi d'autres réglages dans le rc.local
 sudo apt-get install cpufrequtils
modifier rc.local
 cpufreq-set -g performance
 swapoff -a

===QuickScan===

 pi@raspberrypi ~/realtimeconfigquickscan $ perl ./realTimeConfigQuickScan.pl
 == GUI-enabled checks ==
 Checking if you are root... no - good
 Checking filesystem 'noatime' parameter... 3.18.11 kernel - good
 (relatime is default since 2.6.30)
 Checking CPU Governors... CPU 0: 'performance' CPU 1: 'performance' CPU 2:  'performance' CPU 3: 'performance'  - good
 Checking swappiness... 1 - good
 Checking for resource-intensive background processes... none found - good
 Checking checking sysctl inotify max_user_watches... < 524288 - not good
 increase max_user_watches by adding 'fs.inotify.max_user_watches = 524288' to /etc/sysctl.conf and rebooting
 For more information, see http://wiki.linuxaudio.org/wiki/system_configuration#sysctlconf
 Checking access to the high precision event timer... not found - not good
 /dev/hpet not found.
 Checking access to the real-time clock... not found - not good
 /dev/rtc not found (perhaps create a symlink?).
 Checking whether you're in the 'audio' group... yes - good
 Checking for multiple 'audio' groups... no - good
 Checking the ability to prioritize processes with chrt... yes - good
 Checking kernel support for high resolution timers... found - good
 Kernel with Real-Time Preemption... not found - not good
 Kernel without real-time capabilities found
 For more information, see  http://wiki.linuxaudio.org/wiki/system_configuration#installing_a_real-time_kernel
 Checking if kernel system timer is set to 1000 hz... not found - not good
 Try setting CONFIG_HZ to 1000
 
 Checking kernel support for tickless timer... found - good
 == Other checks ==
 Checking filesystem types... ok.
 not found.
 ** Warning: no tmpfs partition mounted on /tmp
    For more information, see:
   - http://wiki.linuxaudio.org/wiki/system_configuration#tmpfs
   - http://lowlatency.linuxaudio.org
 ** Set $SOUND_CARD_IRQ to the IRQ of your soundcard to enable more checks.
   Find your sound card's IRQ by looking at '/proc/interrupts' and lspci.

===CyclicTest===

 pi@raspberrypi  $ sudo cyclictest -a -t -n -p99
 # /dev/cpu_dma_latency set to 0us
 policy: fifo: loadavg: 0.62 0.71 0.64 2/223 2689          
 
 T: 0 ( 2686) P:99 I:1000 C:  30154 Min:     11 Act:   20 Avg:   33 Max:     396
 T: 1 ( 2687) P:99 I:1500 C:  20103 Min:     11 Act:   26 Avg:   26 Max:     136
 T: 2 ( 2688) P:99 I:2000 C:  15077 Min:     11 Act:   17 Avg:   28 Max:     136
 T: 3 ( 2689) P:99 I:2500 C:  12061 Min:     12 Act:   19 Avg:   24 Max:      98

 pi@raspberrypi  $ sudo cyclictest -l1000000 -m -n -a0 -t1 -p99 -i400 -h400 -q
 # /dev/cpu_dma_latency set to 0us
 # Histogram
 # Total: 001000000
 # Min Latencies: 00009
 # Avg Latencies: 00022
 # Max Latencies: 00311
 # Histogram Overflows: 00000
 # Histogram Overflow at cycle number:
 # Thread 0:

==Emlid-raspberryPi2-raspbian-rt==
http://docs.emlid.com/navio/Downloads/Real-time-Linux-RPi2/

Pas moyen de lancer jack pour le moment, affaire à suivre...

=Compilation du noyau depuis la pi=

'''DOCUMENTATION EN COURS'''

==Installation/Configuration==

Test à partir d'une image minibian 2015-11-12-jessie-minibian
*voir par [http://wiki.labomedia.org/index.php/Raspberry_Pi_Installation#Installation_minbian ici] pour les configurations de bases

===Installer les dépendances===
 sudo apt-get install git bc libncurses5-dev gcc make screen ncurses-dev

===Obtenir les sources===
 git clone --depth=1 https://github.com/raspberrypi/linux

==Configuration du noyau==

*A partir du noyau actuel
 zcat /proc/config.gz > ./.config

*A partir de la configuration par défaut du raspberry
pour pi2 
 KERNEL=kernel7 
 make bcm2709_defconfig

pour les autres pi
 KERNEL=kernel
 make bcmrpi_defconfig

==Configurer les options du noyau==
avec une interface pas très simple à naviguer
 make menuconfig

[[File:kernel-config-cpu-scale.png|300px]]

ou une interface plus feng shui
 make nconfig

puis sauvegarder les modifications comme .config


*Sources :<br />
https://www.raspberrypi.org/documentation/linux/kernel/building.md<br />
https://github.com/raspberrypi/linux/tree/rpi-4.1.y<br />

==Compiler le nouveau noyau==
*Compilation (compter ~1h30 pour une pi2)
 make -j4 
(-j4) pour utiliser 4 processus en même temps
ou bien pour créer un paquet (pas encore tester)
 make -j4 deb-pkg

*Créer l'image du noyau et compiler les modules
 make -j4 zImage modules dtbs
 sudo make modules_install

==Copier le nouveau noyau==

 sudo cp arch/arm/boot/dts/*.dtb /boot/
 sudo cp arch/arm/boot/dts/overlays/*.dtb* /boot/overlays/
 sudo cp arch/arm/boot/dts/overlays/README /boot/overlays/
 sudo scripts/mkknlimg arch/arm/boot/zImage /boot/kernel-rt.img

==Configurer le bootloader et tester le nouveau noyau==

*Éditer config.txt
 sudo nano /boot/config.txt
et ajouter
 disable_splash=1
 force_turbo=1
 kernel=kernel-rt.img

*Éditer cmdline.txt et ajouter en début de ligne
 sudo nano /etc/cmdline.txt
 sdhci_bcm2708.enable_llm=0 dwc_otg.speed=1

*Redémarrer et test de version
 sudo reboot
 pi@minibian:~$ cat /proc/version 
 Linux version 4.1.17-v7+ (pi@minibian) (gcc version 4.9.2 (Raspbian 4.9.2-10) ) #1 SMP Tue Feb 16 23:22:53 GMT 2016

==En cas d'erreurs==
*Initialise la compilation mais garde le .config 
 make clean
*Initialise la compilation et supprime le .config
 make mrproper

=Patchage du noyau=
==Télécharger le patch temps réel==
*Il faut tout d'abord connaitre la version actuellement installer sur la pi
 head Makefile -n 3

 uname -r

*Chercher par [https://rt.wiki.kernel.org/index.php/Main_Page ici]

*puis télécharger le patch correspondant
 wget https://www.kernel.org/pub/linux/kernel/projects/rt/4.1/older/patch-4.1.7-rt8.patch.gz
 gunzip patch*


==Appliquer le patch==

 cat patch-4.1.7-rt8.patch | patch -p1

==sources==
https://rt.wiki.kernel.org/index.php/RT_PREEMPT_HOWTO<br />
http://framboisepi.fr/compilation-croise-du-kernel-linux-pour-raspberry-pi-2/<br />
http://connect.ed-diamond.com/GNU-Linux-Magazine/GLMFHS-075/Raspberry-Pi-et-temps-reel<br />
http://2014.capitoledulibre.org/symposion_media/media/coverage/linux-temps-reel-sur-raspberry-pi/Linux_RPi_TR_Capitole2014.pdf<br />

=sources=
http://wiki.linuxaudio.org/wiki/system_configuration#build_your_own_real-time_kernel<br />
https://www.raspberrypi.org/documentation/linux/kernel/building.md<br />
http://www.talkunafraid.co.uk/2014/04/real-time-kernels-and-audio-on-the-raspberry-pi/<br />
http://wiki.linuxaudio.org/wiki/system_configuration#quickscan<br />
http://elinux.org/Raspberry_Pi_Kernel_Compilation<br />
http://www.blaess.fr/christophe/2014/03/06/compilation-native-de-modules-kernel-sur-raspberry-pi/<br />

[[Catégorie:Raspberry_Pi]]