linux-kernel - Re: [PATCH net-next v3 1/2] net/ethernet/realtek: Add Realtek automotive PCIe driver code

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Message-ID: <97f3744d-afbf-4562-9168-5b9e211fac1f@lunn.ch>
Date:   Mon, 21 Aug 2023 15:12:54 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Justin Lai <justinlai0215@...ltek.com>
Cc:     "kuba@...nel.org" <kuba@...nel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next v3 1/2] net/ethernet/realtek: Add Realtek
 automotive PCIe driver code

> Sorry, please allow me to explain again.
> The RTL90xx Series supports I2C, MDC/MDIO and SPI slave to access the registers of Ethernet Switch Core and the external CPU could manage it via these pins.

I was wondering if you had mis-understood my question. The bus
'master' is the device which controls the bus. SPI and MDIO has one
bus master, and there can be multiple clients on the bus. I2C in
theory can have multiple bus masters on one bus, bit it is not done
too often. Your switch is a client.

So my question was, are the bus masters also on PCIE enpoints within
the chip. From an architecture standpoint, it would make sense they
are, all you need is one 4x PCIE slot, and this chip gives you
everything you need. But you can also make use of the SoCs I2C, SPI or
MDIO bus.

    Andrew