On Sun May 01 2022, Vladimir Oltean wrote:
> The Felix VSC9959 switch in NXP LS1028A supports the tc-gate action
> which enforced time-based access control per stream. A stream as seen by
> this switch is identified by {MAC DA, VID}.
>
> We use the standard forwarding selftest topology with 2 host interfaces
> and 2 switch interfaces. The host ports must require timestamping non-IP
> packets and supporting tc-etf offload, for isochron to work. The
> isochron program monitors network sync status (ptp4l, phc2sys) and
> deterministically transmits packets to the switch such that the tc-gate
> action either (a) always accepts them based on its schedule, or
> (b) always drops them.
>
> I tried to keep as much of the logic that isn't specific to the NXP
> LS1028A in a new tsn_lib.sh, for future reuse. This covers
> synchronization using ptp4l and phc2sys, and isochron.
>
> The cycle-time chosen for this selftest isn't particularly impressive
> (and the focus is the functionality of the switch), but I didn't really
> know what to do better, considering that it will mostly be run during
> debugging sessions, various kernel bloatware would be enabled, like
> lockdep, KASAN, etc, and we certainly can't run any races with those on.
>
> I tried to look through the kselftest framework for other real time
> applications and didn't really find any, so I'm not sure how better to
> prepare the environment in case we want to go for a lower cycle time.
> At the moment, the only thing the selftest is ensuring is that dynamic
> frequency scaling is disabled on the CPU that isochron runs on. It would
> probably be useful to have a blacklist of kernel config options (checked
> through zcat /proc/config.gz) and some cyclictest scripts to run
> beforehand, but I saw none of those.
>
> Signed-off-by: Vladimir Oltean <vladimir.oltean@xxxxxxx>
Reviewed-by: Kurt Kanzenbach <kurt@xxxxxxxxxxxxx>
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