Re: [EXT] Re: [net-next] net: dsa: felix: disable always guard band bit for TAS config

On Tue, Apr 20, 2021 at 03:06:40AM +0000, Xiaoliang Yang wrote:

Hi Vladimir.

On Mon, Apr 19, 2021 at 20:38PM +0800, Vladimir Oltean wrote:

quoted

What is a scheduled queue? When time-aware scheduling is enabled on
the port, why are some queues scheduled and some not?

The felix vsc9959 device can set SCH_TRAFFIC_QUEUES field bits to
define which queue is scheduled. Only the set queues serves schedule
traffic. In this driver we set all 8 queues to be scheduled in
default, so all the traffic are schedule queues to schedule queue.

I understand this, what I don't really understand is the distinction
that the switch makes between 'scheduled' and 'non-scheduled' traffic.
What else does this distinction affect, apart from the guard bands added
implicitly here? The tc-taprio qdisc has no notion of 'scheduled'
queues, all queues are 'scheduled'. Do we ever need to set the scheduled
queues mask to something other than 0xff? If so, when and why?