On Tue, 2011-03-08 at 09:57 +0300, Mike Cookson wrote: > On attempt to use device (or even just try 'cat /dev/hpet'), it is > said, that device is busy. But jack has such option :/ > I'm using kernel 2.6.33-rt. I can guess, that under rt kernel i should > not use HPET directly, because it is used by system, > and so, may be referred via 'system'. But even if that, such way could > bring some violations comparing to direct HPET usage. > > May be indeed, HPET should be used directly only on non-rt systems?.. > > Btw, how i specified it: i have jack2 and ladish. Clock is specified > via ladiconf. Clock parameter type is integer; yesterday nedko showed > me a patch for jack, fixing this problem, where i saw order of > variants in enumeration (hpet variant is '2'). Jack's HPET support has an issue: /dev/hpet can only be opened a limited number of times. When you use -c hpet, as well as Jack itself, each client has /dev/hpet opened twice; once as an fd, and once as mmap. On my systems /dev/hpet is limited to 3 or 4 opens, so this is practically unusable for any Jack setup. However you can tell the kernel to use HPET itself for the system clock: echo hpet > /sys/devices/system/clocksource/clocksource0/current_clocksource or put "clocksource=hpet" in your boot up command line. And then -c system will use HPET, indirectly. Peter.
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