port-evbarm/55263: BeagleBone Black too many interrupts on CPU when using 5V DC power cable

[cryintothebluesky%gmail.com@localhost]

>Number:         55263
>Category:       port-evbarm
>Synopsis:       BeagleBone Black too many interrupts on CPU when using 5V DC power cable
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    port-evbarm-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu May 14 16:20:01 +0000 2020
>Originator:     Sad Clouds
>Release:        9.0
>Organization:
>Environment:
>Description:
I see a strange issue with NetBSD-9.0 on BeagleBone Black. When it is powered via USB cable, everything is OK and CPU is normally idle.

But when it is powered via 5V DC cable, about 30-40% of CPU is constantly consumed by interrupts (as reported by top).

Looking at output of "vmstat -iv" the only thing I notice is "irq 64" which is a bit higher (34 vs 7) when powered via 5V DC:

5V DC:
$ vmstat -iv
interrupt           total rate
intc (cpu0) irq 98      0    0
intc (cpu0) irq 96      0    0
intc (cpu0) irq 32      0    0
intc (cpu0) irq 62      0    0
intc (cpu0) irq 70      0    0
intc (cpu0) irq 12   1723   10
intc (cpu0) irq 72      1    0
intc (cpu0) irq 30      0    0
intc (cpu0) irq 40      0    0
intc (cpu0) irq 41   1143    6
intc (cpu0) irq 42    884    5
intc (cpu0) irq 43      0    0
intc (cpu0) irq 64   5625   34
intc (cpu0) irq 28     41    0
intc (cpu0) irq 18   2143   12
intc (cpu0) irq 19      1    0
intc (cpu0) irq 69  16324   98
intc (cpu0) irq 3       0    0
Total               27885  169

>How-To-Repeat:

>Fix: