linux-kernel - Re: [PATCH net-next] net: ethernet: ti: cpsw: enable vlan rx vlan offload

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Message-ID: <20180316002935.GB13119@lunn.ch>
Date:   Fri, 16 Mar 2018 01:29:35 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Grygorii Strashko <grygorii.strashko@...com>
Cc:     "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        Sekhar Nori <nsekhar@...com>, linux-kernel@...r.kernel.org,
        linux-omap@...r.kernel.org
Subject: Re: [PATCH net-next] net: ethernet: ti: cpsw: enable vlan rx vlan
 offload

On Thu, Mar 15, 2018 at 03:15:50PM -0500, Grygorii Strashko wrote:
> In VLAN_AWARE mode CPSW can insert VLAN header encapsulation word on Host
> port 0 egress (RX) before the packet data if RX_VLAN_ENCAP bit is set in
> CPSW_CONTROL register. VLAN header encapsulation word has following format:
> 
>  HDR_PKT_Priority bits 29-31 - Header Packet VLAN prio (Highest prio: 7)
>  HDR_PKT_CFI 	  bits 28 - Header Packet VLAN CFI bit.
>  HDR_PKT_Vid 	  bits 27-16 - Header Packet VLAN ID
>  PKT_Type         bits 8-9 - Packet Type. Indicates whether the packet is
>                  	VLAN-tagged, priority-tagged, or non-tagged.
> 	00: VLAN-tagged packet
> 	01: Reserved
> 	10: Priority-tagged packet
> 	11: Non-tagged packet
> 
> This feature can be used to implement TX VLAN offload in case of
> VLAN-tagged packets and to insert VLAN tag in case Non-tagged packet was
> received on port with PVID set. As per documentation, CPSW never modifies
> packet data on Host egress (RX) and as result, without this feature
> enabled, Host port will not be able to receive properly packets which
> entered switch non-tagged through external Port with PVID set (when
> non-tagged packet forwarded from external Port with PVID set to another
> external Port - packet will be VLAN tagged properly).

So, i think it is time to discuss the future of this driver. It should
really be replaced by a switchdev/DSA driver. There are plenty of
carrots for a new driver: Better statistics, working ethtool support
for all the PHYs, better user experience, etc. But maybe now it is
time for the stick. Should we Maintainers decide that no new features
should be added to the existing drivers, just bug fixes?

       Andrew