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

[Vladimir Oltean]

Hi Xiaoliang,

On Mon, Apr 19, 2021 at 06:25:30PM +0800, Xiaoliang Yang wrote:
> ALWAYS_GUARD_BAND_SCH_Q bit in TAS config register is descripted as
> this:
> 	0: Guard band is implemented for nonschedule queues to schedule
> 	   queues transition.
> 	1: Guard band is implemented for any queue to schedule queue
> 	   transition.
>
> The driver set guard band be implemented for any queue to schedule queue
> transition before, which will make each GCL time slot reserve a guard
> band time that can pass the max SDU frame. Because guard band time could
> not be set in tc-taprio now, it will use about 12000ns to pass 1500B max
> SDU. This limits each GCL time interval to be more than 12000ns.
>
> This patch change the guard band to be only implemented for nonschedule
> queues to schedule queues transition, so that there is no need to reserve
> guard band on each GCL. Users can manually add guard band time for each
> schedule queues in their configuration if they want.
>
> Signed-off-by: Xiaoliang Yang <xiaoliang.yang_1@xxxxxxx>
> ---

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