linux-kernel - Re: [RFC PATCH net-next 01/28] docs: networking: ti: add driver doc for CPSW Proxy Client

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Date: Tue, 21 May 2024 17:42:03 +0530
From: Siddharth Vadapalli <s-vadapalli@...com>
To: Andrew Lunn <andrew@...n.ch>
CC: Siddharth Vadapalli <s-vadapalli@...com>, <davem@...emloft.net>,
        <edumazet@...gle.com>, <kuba@...nel.org>, <pabeni@...hat.com>,
        <corbet@....net>, <rogerq@...nel.org>, <danishanwar@...com>,
        <vladimir.oltean@....com>, <netdev@...r.kernel.org>,
        <linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <vigneshr@...com>,
        <misael.lopez@...com>, <srk@...com>
Subject: Re: [RFC PATCH net-next 01/28] docs: networking: ti: add driver doc
 for CPSW Proxy Client

On Sun, May 19, 2024 at 05:31:16PM +0200, Andrew Lunn wrote:
> On Sat, May 18, 2024 at 06:12:07PM +0530, Siddharth Vadapalli wrote:
> > The CPSW Proxy Client driver interfaces with Ethernet Switch Firmware on
> > a remote core to enable Ethernet functionality for applications running
> > on Linux. The Ethernet Switch Firmware (EthFw) is in control of the CPSW
> > Ethernet Switch on the SoC and acts as the Server, offering services to
> > Clients running on various cores.
> 
> I'm not sure we as a community what this architecture. We want Linux
> to be driving the hardware, not firmware. So expect linux to be
> running the server.
> 
> > +The "am65-cpsw-nuss.c" driver in Linux at:
> > +drivers/net/ethernet/ti/am65-cpsw-nuss.c
> > +provides Ethernet functionality for applications on Linux.
> > +It also handles both the control-path and data-path, namely:
> > +Control => Configuration of the CPSW Peripheral
> > +Data => Configuration of the DMA Channels to transmit/receive data
> 
> So nuss is capable of controlling the hardware. nuss has an upper
> interface which is switchdev, and a lower interface which somehow acts
> on the hardware, maybe invoking RPCs into the firmware?
> 
> So it is not too big a step to put the server functionality in Linux,
> on top of the nuss driver.

Andrew,

Thank you for reviewing the patch and sharing your feedback. While I
have come across other Switch Designs / Architecture, I am yet to go
through the one you have mentioned below. I will go through it in detail
and will follow up with my understanding in a future reply. This reply
is intended to be an acknowledgment that I have read your feedback.
I also wanted to clarify the use-case which this series targets. The
requirements of the use-case are:
1. Independent Ethernet Switch functionality: Switch operation and
configuration when Linux is not functional (Fast startup, Low Power
Mode, Safety use-cases).
2. Dynamic Ethernet Switch configuration changes performed based on the
applications which run on various cores.

[...]

Regards,
Siddharth.