On 6/9/20 11:27 AM, Jeremy Jongepier wrote:
Hello Tim,
My understanding is that ALSA placed a hard-coded limit on the
snd-hrtimer of around 1024Hz a couple of years ago.
The snd-hrtimer used to be able to be set very high frequencies
until one day it wouldn't. I contacted ALSA and they told me
about this new hard-coded limit.
This sent me scrambling to re-order the midi timer preference
in MusE because it seems the RTC timer is now the only timer
that can give you anything above 1024Hz.
Have I got this correct?
I checked sound/core/hrtimer.c of a current linux kernel source and I
don't see any limits of 1000 or 1024. And when I check on my system with
`cat /proc/asound/timers` I see the resolution of the system timer is
1000 µs, so 1 ms (which I think equals the 1000 HZ kernel setting I use)
while the HR timer has a resolution of 0.001 µs, so 1 ns. If I search
for .resolution in /proc/timer_list I see that same value, so 1 ns. So
my guess is that snd-hrtimer goes way beyond 1000 HZ and doesn't seem to
have a hard-coded limit of itself.
Best,
Jeremy
Hi, yes I got the same 'normal' reported resolution and frequencies
but behind the scenes it had the hard-coded limit.
I pointed that out to ALSA, that there is no indication at all that this
limit is applied,
until one actually tries to use it.
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