[LAU] 1. Linux-Rt and TSC - 2. Linux-Rt and IRQ allocation

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To: linux-audio-user <linux-audio-user@...>
Date: Wednesday, January 22, 2014 - 12:39 pm

Hi,

there are 2 things I don't understand.

1. Linux-Rt and TSC
===================

All Rt kernels for all Linux distros I use seem to have an issue
regarding to TSC.

I wonder what to do, to get rid of those messages, IOW how to fix the
issue.

E.g. Debian 32-bit architecture

root@debi386:/mnt/arch/home/rocketmouse/Desktop# dmesg | grep TSC
[ 0.000000] Fast TSC calibration using PIT
[ 0.000000] Marking TSC unstable due to TSCs unsynchronized
root@debi386:/mnt/arch/home/rocketmouse/Desktop# grep TSC /var/log/messages
Jan 16 09:28:08 debi386 kernel: [ 0.000000] tsc: Fast TSC calibration using PIT
Jan 16 09:28:08 debi386 kernel: [ 0.000000] tsc: Marking TSC unstable due to TSCs unsynchronized
Jan 16 09:28:08 debi386 kernel: [ 0.003000] calibrate_delay_direct() ignoring timer_rate as we
had a TSC wrap around start=4287833042 >=post_end=13864416
Jan 16 09:50:58 debi386 kernel: [ 0.000000] tsc: Fast TSC calibration using PIT
Jan 16 09:50:58 debi386 kernel: [ 0.000000] tsc: Marking TSC unstable due to TSCs unsynchronized
Jan 22 12:05:33 debi386 kernel: [ 0.000000] Fast TSC calibration using PIT
Jan 22 12:05:33 debi386 kernel: [ 0.000000] Marking TSC unstable due to TSCs unsynchronized

Jan 22 are messages when booted to kernel 3.2.0-4-rt-686-pae i686 from
the repositories.
Jan 16 might be a broken kernel 3.8.13-rt14-pae-rocketmouse I build
based on a 3.8.13-rt14 x86_64 config.

E.g. Arch Linux 64-bit architecture

On startup I see "x86 Rt requires FEATURE_CONSTANT_TSC" or similar for
Arch Linux Rt kernels from the repositories and for the once I build.

This link for Chromebooks was the best explanation I found:
http://www.chromium.org/chromium-os/how-tos-and-troubleshooting/tsc-resy...

root@debi386:/mnt/arch/home/rocketmouse/Desktop# grep tsc /proc/cpuinfo
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge
mca cmov pat pse36 clflush mmx fxsr sse sse2 ht
syscall nx mmxext fxsr_opt rdtscp lm 3dnowext 3dnow
extd_apicid pni cx16 lahf_lm cmp_legacy svm extapic
cr8_legacy 3dnowprefetch lbrv
flags : [snip] tsc [snip]

2. Linux-Rt and IRQ allocation
==============================

All kernels I used in the last years for *buntu, Debian and Arch Linux
<= 3.8.13-rt14 (kernels > 3.8.13-rt14 don't work on my machine) give my
graphics it's own IRQ, the Debian kernel 3.2.0-4-rt-686-pae doesn't.

What options do I need to enable, so that it will allocate the graphics
it's own IRQ too, instead of sharing it with the RME card?

Regards,
Ralf

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[LAU] 1. Linux-Rt and TSC - 2. Linux-Rt and IRQ allocation, Ralf Mardorf, (Wed Jan 22, 12:39 pm)