Re: [PATCH v7 00/10] Introduce the Counter subsystem

From: David Lechner
Date: Mon Jul 02 2018 - 14:13:50 EST

On 06/21/2018 04:06 PM, William Breathitt Gray wrote:
I decided to strip down these devices to arrive at the core essence of
what constitutes a "counter device" and therefore design a "generic
counter" abstraction to better represent these devices and prevent the
ambiguity we discovered with the existing IIO Counter interface. This
abstraction became the Generic Counter paradigm, which is explained in
detail within the Documentation/driver-api/generic-counter.rst file
introduced by this patchset.

I'm curious if you have given any thought to the time aspect of counters.
I am interested in the rate at which the counters are counting (e.g. how
many counts per second). I realize that you can calculate this in
userspace or in the kernel using the system timer, but it is not very
accurate since Linux is not a realtime OS. So, I would like to get the
rate directly from the hardware. For example, the TI eQEP[1], like the
one found in BeagleBones, has a couple ways of measuring time (see link
for details).