linux-kernel - RE: [PATCH net-next v19 01/13] rtase: Add pci table supported in this module

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Date: Thu, 23 May 2024 06:29:55 +0000
From: Larry Chiu <larry.chiu@...ltek.com>
To: Andrew Lunn <andrew@...n.ch>
CC: Justin Lai <justinlai0215@...ltek.com>,
        "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>,
        "jiri@...nulli.us" <jiri@...nulli.us>,
        "horms@...nel.org" <horms@...nel.org>,
        Ping-Ke Shih <pkshih@...ltek.com>
Subject: RE: [PATCH net-next v19 01/13] rtase: Add pci table supported in this module


> > Thank you very much for your clear reply.
> >
> > As I mentioned, it works like a NIC connected to an Ethernet Switch, not a
> > Management port.
> > The packets from this GMAC are routed according to switch rules such as
> > ACL, L2, .... and it does not control packet forwarding through any special
> > header or descriptor. In this case, we have our switch tool which is used
> > for provisioning these rules in advance. Once the switch boots up, the
> > rules will be configured into the switch after the initialization. With this
> > driver and the provisioning by our switch tool, it can make switch forward
> > the frame as what you want. So it's not a DSA like device.
> 
> How does spanning tree work? You need to send bridge PDUs out specific
> ports. Or do you not support STP and your network must never have
> loops otherwise it dies in a broadcast storm? That does not sound very
> reliable.
> 
> There are other protocols which require sending packets out specific
> ports. Are they simply not supported?
> 
This port is not a CPU port, nor a management port, and therefore does not 
manage any protocols of the switch. These protocols are implemented by the
CPU inside the Ethernet switch core.

> > In another case, we do have other function which is used for controlling
> > the switch registers instead of sending packets from the switch ports.
> > At the meanwhile, we are investigating how to implement the function to
> > Integrate into switchdev.
> 
> In general, we don't support configuration of hardware from user
> space, which is what your switch tool sounds like. We will want to see
> a switchdev driver of some form.
> 
> It might be you need to use VLAN overlays, using
> net/dsa/tag_8021q.c. Each port of the switch is given a dedicated
> VLAN, and the switch needs to add/strip the VLAN header. Its not
> great, but it does allow 'simple' switches to have basic functionality
> if they are missing header/dma descriptor support for selecting ports.
> 
>         Andrew

Typically, a NIC connected to the network may go through a switch, as show
below. Our design saves the two PHYs in the middle and connects to the Host
through PCIe.

This driver just service the transmit/receive packets for one port in the RTL90xx
with PCIe interface. Other programs that the switch needs to execute are
managed by the CPU inside the switch core.

*               *************************
*               *                       *
*               *        PC/Host        *
*               *                       *
*               *   +-------------+     *
*               *   |      NIC    |     *
*               ***********++************
*                        | PHY |
*                          ||
*                        | PHY |                  
*            +-------------++----------------+    
*            |           | MAC |             |    
*            |           +-----+             |    
*            |                               |    
*            |     Ethernet Switch Core      |    
*            |                               |    
*            |   +-----+           +-----+   |    
*            |   | MAC |...........| MAC |   |    
*            +---+-----+-----------+-----+---+    
*                | PHY |...........| PHY | 

                            |
                            |
                            |
                            V

*               *************************
*               *                       *
*               *        PC/Host        *
*               *                       *
*               *   +-------------+     *
*               *   |      NIC    |     *
*               ***********++************
*                          ||
*            +-------------++----------------+    
*            |           | MAC |             |    
*            |           +-----+             |    
*            |                               |    
*            |     Ethernet Switch Core      |    
*            |                               |    
*            |   +-----+           +-----+   |    
*            |   | MAC |...........| MAC |   |    
*            +---+-----+-----------+-----+---+    
*                | PHY |...........| PHY |