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SubjectRe: [PATCH] dpaa2-ethsw: move the DPAA2 Ethernet Switch driver out of staging
Date
On 8/12/19 4:57 PM, Andrew Lunn wrote:
>> In the DPAA2 architecture MACs are not the only entities that can be
>> connected to a switch port.
>> Below is an exemple of a 4 port DPAA2 switch which is configured to
>> interconnect 2 DPNIs (network interfaces) and 2 DPMACs.
>>
>>
>> [ethA] [ethB] [ethC] [ethD] [ethE] [ethF]
>> : : : : : :
>> : : : : : :
>> [eth drv] [eth drv] [ ethsw drv ]
>> : : : : : : kernel
>> ========================================================================
>> : : : : : :
>> hardware
>> [DPNI] [DPNI] [============= DPSW =================]
>> | | | | | |
>> | ---------- | [DPMAC] [DPMAC]
>> ------------------------------- | |
>> | |
>> [PHY] [PHY]
>>
>> You can see it as a hardware-accelerated software bridge where
>> forwarding rules are managed from the host software partition.
>
> Hi Ioana

Hi Andrew,

>
> What are the use cases for this?
>
> Configuration is rather unintuitive. To bridge etha and ethb you need
> to
>
> ip link add name br0 type bridge
> ip link set ethc master br0
> ip link set ethd master br0
>
> And once you make ethc and ethd actually send/receive frames, etha and
> ethc become equivalent.
>
> If this was a PCI device, i could imagine passing etha into a VM as a
> PCI VF. But i don't think it is PCI?

Indeed it's not PCI but we can pass etha to a VM. That's the main use
case of having DPNIs connected to a switch object.

Our direct assignment solution for DPAA2 is not upstream yet (the case
with many of our drivers :) ) but the main idea is exposing to the VM a
fsl-mc bus on which it can find any DPAA2 objects needed to configure a
network interface (using firmware calls).


>
> I'm not sure moving etha into a different name space makes much sense
> either. My guess would be, a veth pair with one end connected to the
> software bridge would be more efficient than DMAing the packet out and
> then back in again. >
> Thanks
> Andrew
>


That's really an interesting test to be made since we can make a veth
pair from DPAA2 objects just connecting two DPNIs back to back. I'll
make some performance tests and compare against the software veth.


Thanks,
Ioana



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