[LAD] timers

Ralf Mardorf ralf.mardorf at alice-dsl.net
Sat Nov 7 21:40:46 UTC 2009


I guess my mobo supports hpet :).

$ dmesg | grep -i hpet
[    0.000000] ACPI: HPET 77EE89C0, 0038 (r1 ATI    ASUSACPI 42302E31 
AWRD       98)
[    0.000000] ACPI: HPET id: 0x8200 base: 0xfed00000
[    0.000999] hpet clockevent registered
[    0.000999] HPET: 4 timers in total, 0 timers will be used for 
per-cpu timer
[    0.177117] hpet0: at MMIO 0xfed00000, IRQs 2, 8, 0, 0
[    0.177123] hpet0: 4 comparators, 32-bit 14.318180 MHz counter
[    1.166497] rtc0: alarms up to one month, 242 bytes nvram, hpet irqs

1. The kernel has to support it too.
2. If the kernel-rt does support it, I need to add a startup script:

    chgrp audio /dev/hpet
    echo 1024 > /proc/sys/dev/hpet/max-user-freq
    modprobe snd-hrtimer

Here I don't understand what the value 1024, written to max-user-freq 
does mean ;).

3. I need to launch JACK2 with the option "-c", e.g.:

jackd -Rc h -dalsa -dhw:0 -r96000 -p512 -n2 -Xseq

4. The sequencer timing source needs to be set up to hpet or hrtimer too?
rosegarden -v 1.7.3 and qtractor -v aren't able to do it?

Or will the "-c" option for JACK2 replace a chosen timer for Qtractor or 
Rosegarden with hpet?


"With a Linux kernel, you need the newer "rtc-cmos" hardware clock 
device driver rather than the original "rtc" driver." 

I guess this is within the vanilla kernel source code?!


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