On 6/9/20 5:36 PM, Tim E. Real wrote:
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.
FYI Here's the thread from 2017,
maybe things have changed since then?
https://www.alsa-project.org/pipermail/alsa-devel/2017-May/120949.html
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