[LAU] XanMod kernel

Tim E. Real termtech at rogers.com
Tue Jun 9 23:36:37 CEST 2020

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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