Messages in this thread | | | Date | Fri, 9 Jun 2023 19:16:04 +0200 | From | Andrew Lunn <> | Subject | Re: [PATCH net-next 2/2] net: dsa: mv88e6xxx: implement egress tbf qdisc for 6393x family |
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> Yes, I can do that (or maybe -EINVAL to match Vladimir's comment ?). I think > it's worth mentioning that I encountered an issue regarding those values during > tests: I use tc program to set the tbf, and I observed that tc does not even > reach kernel to set the qdisc if we pass no burst/latency value OR if we set it > to 0. So tc enforces right on userspace side non-zero value for those > parameters, and I have passed random values and ignored them on kernel side.
That is not good. Please take a look around and see if any other driver offloads TBF, and what they do with burst.
> Checking available doc about tc-tbf makes me feel like that indeed a TBF qdisc > command without burst or latency value makes no sense, except my use case can > not have such values. That's what I struggled a bit to find a proper qdisc to > match hardware cap. I may fallback to a custom netlink program to improve testing.
We don't really want a custom application, since we want users to use TC to set this up.
Looking at the 6390 datasheet, Queue Counter Registers, mode 8 gives the number of egress buffers for a port. You could validate that the switch has at least the requested number of buffers assigned to the port? There is quite a bit you can configure, so maybe there is a way to influence the number of buffers, so you can actually implement the burst parameter?
Andrew
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