Am Sonntag, 19. Januar 2020 09:20:58 UTC+1 schrieb Andrew P. Lentvorski:
>
> Well, sort of, except you omit the *EXTREMELY* important point that you 
> install a custom kernel module in order to expose the clock activation and 
> pinmux system to all users.
>

That's not correct. Only users with write access to the sysfs entry can 
pinmux. By default that're members of the pruio system group.
  

> Okay, yes, if I build a kernel module I now have full access to all 
> registers on the system with no restrictions.  That's sort of like swatting 
> a fly with an H-Bomb, but it will work.
>

It was your idea to use the PRU-IEP module. I recommended to use a pin on a 
GPIO-SS. Yet, you didn't explain why the L3/L4 latency isn't aceptable for 
your target.

This means that config-pin has a fairly significant bug in not being able 
> to route the IEP pins.  Has that bug ever been filed anywhere?
>

config-pin isn't able to set lots of useful pin configurations, and has 
lots of bugs. Ie. you can set GPIO for P9_42 and P9_92 in oposite output 
states and damage the CPU. C. Steinkuehler didn't develop that tool with a 
standard solution in mind. At the beginning it was a work-aroung, and only 
cosmetic changes were done.

Anyway, you can pinmux at boot-time by writing, compiling and installing a 
customized device tree overlay. The tool 
http://users.freebasic-portal.de/tjf/Projekte/libpruio/doc/html/dts__custom_8bas.html
 
may be helpful in that case.

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