linux-kernel - Re: [PATCH net-next] net: stmmac: qcom-ethqos: Add sysfs nodes for qcom ethqos

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Message-ID: <dd585977-50c4-40a4-a664-0ecb5a84807a@quicinc.com>
Date:   Fri, 8 Dec 2023 11:58:26 +0530
From:   Sneh Shah <quic_snehshah@...cinc.com>
To:     Andrew Lunn <andrew@...n.ch>
CC:     Vinod Koul <vkoul@...nel.org>,
        Bhupesh Sharma <bhupesh.sharma@...aro.org>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Jose Abreu <joabreu@...opsys.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        <netdev@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <kernel@...cinc.com>,
        Andrew Halaney <ahalaney@...hat.com>, <andersson@...nel.org>
Subject: Re: [PATCH net-next] net: stmmac: qcom-ethqos: Add sysfs nodes for
 qcom ethqos



On 12/6/2023 7:22 PM, Andrew Lunn wrote:
> On Wed, Dec 06, 2023 at 05:17:25PM +0530, Sneh Shah wrote:
>>
>>
>> On 12/5/2023 8:38 PM, Andrew Lunn wrote:
>>> On Mon, Dec 04, 2023 at 02:18:54PM +0530, Sneh Shah wrote:
>>>> Add sysfs nodes to conifigure routing of specific vlan id to GVM queue.
>>>> GVM queue is not exposed to PVM stmmac, so TC ops can't configure routing.
>>>
>>> Adding files in /sysfs has ~0 chance of being accepted.
>>>
>>> As requested, please explain what all these different hardware blocks
>>> are, and what you are trying to achieve. We can then recommend the
>>> correct interface.
>>>
>>>     Andrew
>>>
>>> ---
>>> pw-bot: cr
>>
> 
>> We have multiVM Architecture here. PVM will have stmmac running with
>> 4 Rx Tx queues. stmmac in PVM is responsible to configure whole
>> ethernet HW MAC/DMA/MTL ( including clocks, regulators and other
>> core bsp elements).
> 
> Please remember that stmmac is mostly used in embedded systems. People
> used to embedded systems generally don't know virtual machine
> terminology. So please spell out what PBM, GVM, etc mean.
> 
>> In GVM we have thin Ethernet driver, which is responsible to
>> configure and manage only 1 Rx/TX queue, i.e 5th Rx/Tx ethernet
>> queue. GVM can't access any other resisters apart from this 5th
>> queue specific MTL and DMA registers.
>  
>> We need to route vlan traffic of a specific Priority to GVM Queue
>> (Ethernet queue 5) via programming a MAC register. The MAC register
>> is not accessible in GVM and has to be programmed from PVM. stmmac
>> already has TC OPS to program this routing via vlan
>> priority. However, as PVM has only 4 queues enabled, TC tool will
>> not take 5th queue as input. Hence, these nodes were added to
>> conifure the MAC register to route specific vlan packets to 5th
>> queue in GVM.
>  
>> Note: The queues mentioned above are HW MTL Queues and DMA
>> Channels. The routing can be done in the HW itself based on vlan pcp
>> before the packets reach to driver.
> 
> Is the normal way you would do this is like this:
> 
> tc qdisc add dev eth1 parent root handle 100 \
> mqprio num_tc 4 \
> map 0 1 2 3 0 0 0 0 0 0 0 0 0 0 0 0 \
> queues 1@0 1@1 1@2 1@3 \
> hw 1
> 
> But you are saying that you cannot extend this to 5 queues?
> 
>     Andrew

Yes this can't extend to 5 queues. Because, stmmac in primary virtual machine will only have 4 netdev queues. So TC won't take input for 5th queue.