Re: [PATCH v3 5/8] net: dsa: hellcreek: Add TAPRIO offloading support

On Tue Aug 25 2020, Vladimir Oltean wrote:

Hi Vinicius,

On Mon, Aug 24, 2020 at 04:45:50PM -0700, Vinicius Costa Gomes wrote:

quoted

Kurt Kanzenbach [off-list ref] writes:

quoted

With TAPRIO traffic classes and the mapping to queues can be
configured. The switch can also map traffic classes. That sounded like a
good match to me.

The only reason I could think that you would need this that *right now*
taprio has pretty glaring oversight: that in the offload parameters each entry
'gate_mask' reference the "Traffic Class" (i.e. bit 0 is Traffic Class
0), and it really should be the HW queue.

Sorry, but could you please explain why having the gate_mask reference
the traffic classes is a glaring oversight, and how changing it would
help here?

Also, Kurt, could you please explain what the
HR_PRTCCFG_PCP_TC_MAP_SHIFT field in HR_PRTCCFG is doing?
To me, it appears that it's configuring ingress QoS classification on
the port (and the reason why this is strange to me is because you're
applying this configuration through an egress qdisc), but I want to make
sure I'm not misunderstanding.

All the TSN operations in the switch such as the gate control work on
internally on traffic classes. The traffic class is determined by the
PCP field on the VLAN tagged frames. This mapping is configurable via
the pcp to tc map. And the TC also defines the hardware queue.

Thanks,
Kurt