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

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Message-ID: <5d5f3955-fc30-428c-99f4-42f9b7580a84@quicinc.com>
Date:   Wed, 6 Dec 2023 17:17:25 +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 12/5/2023 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).
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.