Raspberry Pi Forums

tom.k.cook wrote:With what settings did you run cyclictest?

meki_RPI wrote:i tried to add kernel=zImage-3.8.13-rt11 to /boot/config.txt (there are no #kernel.... in the file)
but RPi can not boot. Can someone please give me an advise, How can i correctly change/add the row kernel=....?

i also have got these message during booting of new SD-Card:
drivers/rtc/hctosys.c: unabile to open rtc device (rtc0)
Waiting ofr root device /dev/mmcblk0p2...

best regards

mung wrote:

meki_RPI wrote:i tried to add kernel=zImage-3.8.13-rt11 to /boot/config.txt (there are no #kernel.... in the file)
but RPi can not boot. Can someone please give me an advise, How can i correctly change/add the row kernel=....?

i also have got these message during booting of new SD-Card:
drivers/rtc/hctosys.c: unabile to open rtc device (rtc0)
Waiting ofr root device /dev/mmcblk0p2...

best regards

1) I think you need to put the kernel= in /boot/cmdline.txt (I normally use a different method so am not sure)
2) I think your kernel will not work anyway you need to make sure you patch with the autostatic patch or llm=0 otherwise SD will deadlock, and if you have hctosys.c error you need to config your kernel better without that option in menuconfig step of kernel compile

p.s. autostatic patch will fail and you need to edit by hand using the .rej files to workout what needs to be changed in the source code (quite simple and should only take 5 mins once you know what you are doing).

meki_RPI wrote:Hello,
I got the PREEMT RT Kernel but not really a satified result of latency.

with this test: cyclictest -p95 -n -l 1000000
# /dev/cpu_dma_latency set to 0us
policy: fifo: loadavg: 0.56 0.42 0.31 2/174 2480
T: 0 ( 2480) P:95 I:1000 C: 18375 Min: 14 Act: 54 Avg: 42 Max: 3529

The max latency is much more than i ran RPi without RT-Kernel.
Can someone explain it please.
best regards

kansky wrote:Seems as if someone claims good preempt_rt latency on RaspberryPi. See here:

http://www.spinics.net/lists/linux-rt-u ... 11200.html

Zaine.RPi wrote:

Code: Select all

drivers/usb/host/dwc_otg/dwc_otg_hcd_linux.c: In function 'hcd_init':
drivers/usb/host/dwc_otg/dwc_otg_hcd_linux.c:461: error: 'INTERRUPT_VC_USB' undeclared (first use in this function)

Please help, thank you.[/quote]
This sort of question is almost useless, you really need to provide lots more information!
You should give a few details about your experience in compiling kernels (newbie,done it a few times, or expert)
Which kernel you use(where you download it from?), which patch you used, which platform you compile on, what kernel config, which instructions are you following?

I doubt I can help much as I am quite a newbie, but I will tell you what I would do.
First try compiling the kernel without the RT patch, does it work??
If it does not then you need to sort out your .config, if it does work
Try using the config from a running raspbian system using cat /proc/config.gz >> .config

If you get a working vanilla kernel, do a make clean, then tar.gz the source tree, then apply the patch you want to use.
Once the patch is applied check all the .rej files (find ./ -name *.rej -print), workout what you need to fix by hand if necessary.

Then run a make menuconfig and check all the options, there still maybe config problems as it seems some menuconfig options are not added so you may get questions at the command line (probably best to use the defaults?)

My guess is if you have done everything correctly as far as patching then the problem is a missed .config option that the USB system depends on. I have no idea really, you probably best reading the code in the relevant source files and reading the .config and the menu help for all options related to USB when doing a menuconfig?

I should say that as far as I have found the patch never applies clean, and its possible the problems I seem to have could be due to my incorrectly manual patching (I think required addition of spinlock_irqsave, maybe I should not have manually patched?)

The realtime performance sucks if you do get it to compile and boot (according to cyclictest max latency spikes can be huge, don't know why?) average latency does seem fair most of the time though.

As far as I am aware the 3.2.27 still seems to have best lowest 'max latency' there can be problems with keypresses on usb ketboards and other stuff I think I already said in this thread.

Of course there is the possibility that your error is something new due to the code gods of the raspberry kernel trying to fix RT_PREEMPT performance, maybe you just need to get the right config options?

fj.rojas wrote:Thanks to this post, some months ago I could successfully install the rt-11 with the 3.8.13 kernel patch in RPi. I attach the procedure I followed with the required sdhci.c file. Thank you!

Zaine.RPi wrote: I proceeded exactly according to your procedures, but when I turn on the Raspberry Pi, the screen only displays colored stripes (really exactly according to the attached file). Do you know where is the problem?
http://postimg.org/image/wdp0ipnd7/

Zaine.RPi wrote: -rw-r--r-- 1 notebook notebook 2921616 Mar 9 17:25 zimage-3.8.13-rt11

mung wrote:

Zaine.RPi wrote: -rw-r--r-- 1 notebook notebook 2921616 Mar 9 17:25 zimage-3.8.13-rt11

I have no idea really, have you tried login on serial console?

If you cannot login over serial then you have not configured the kernel correctly and it is just not loading, if you can login on serial then there is problem with the framebuffer initialisation.

Do not assume I know what I am talking about, I am just guessing, I have no real understanding of how the kernel works.

minhnt152 wrote:Dear fj.rojas,

I'm new to linux,

So i dont understand much about the procedure.
Is your procedure run on an ubuntu pc then it will create a RT image for RPi?

Thanks

twobob wrote:I have a Linux RASPBERRYPI 3.12.20+ #687 PREEMPT Fri May 30 16:39:11 BST 2014 armv6l GNU/Linux

I see vague reference to kernel-rt-3.12.20-0.rt30.1 on google...

Which is the right set of patches to apply to the kernel at the moment?

Partial noob, done some kernel compiles/x-compiles/patching before on other embedded devices.

Thanks.

Or is there an image out there somewhere that someone is kind enough to share? Thanks again.