netdev - Re: [PATCH] net: phy: b53: switchdev driver for Broadcom BCM53xx switches

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Date:	Wed, 25 Feb 2015 08:03:48 +0100
From:	Rafał Miłecki <zajec5@...il.com>
To:	Florian Fainelli <f.fainelli@...il.com>
Cc:	Andrew Lunn <andrew@...n.ch>,
	Andy Gospodarek <gospo@...ulusnetworks.com>,
	"David S. Miller" <davem@...emloft.net>,
	Network Development <netdev@...r.kernel.org>,
	Jonas Gorski <jogo@...nwrt.org>,
	Hauke Mehrtens <hauke@...ke-m.de>,
	Felix Fietkau <nbd@...nwrt.org>, Jiri Pirko <jiri@...nulli.us>
Subject: Re: [PATCH] net: phy: b53: switchdev driver for Broadcom BCM53xx switches

On 25 February 2015 at 01:39, Florian Fainelli <f.fainelli@...il.com> wrote:
> On 24/02/15 16:15, Andrew Lunn wrote:
>> On Tue, Feb 24, 2015 at 02:55:58PM -0800, Florian Fainelli wrote:
>>> On 24/02/15 14:50, Rafa?? Mi??ecki wrote:
>>>> As said in the commit message, these switches are really simple
>>>> devices. We can't actually send packets to the particular ports
>>>> (unless something has changed in the more recent hardware).
>>>
>>> These switches all support Broadcom tags, so you could use your host CPU
>>> Ethernet MAC to send/receive packets to/from specific ports of the
>>> switch, and then this is just like DSA, but everything that you say
>>> below is true.
>>
>> If this hardware does support the concept of tags compatible to the
>> existing Broadcom Starfighter 2, should we not do that? Is there a
>> good reason these chips should use a difference abstraction than
>> Starfighter 2 and the Marvell devices?
>
> No, I think that would be a reasonable thing to do, I am still a little
> unclear how the older BCM5325 and friends work with respect to broadcom
> tags, but regardless, DSA now understands switches that do not support
> tags, so we should be good with some sort of b53 library.

DSA doesn't allow me to use switch (hardware) VLANs. I would need to
handle all forwarding in CPU. The most powerful Broadcom MIPS SoC -
BCM4706 - can handle about 130 Mb/s. Less powerful - BCM4718A1 - only
about 50 Mb/s.
This is way too bad for performance when there is a 1 Gb/s switch and
too bad for CPU usage.

I guess the whole idea of switchdev was to allow what proposed version
of b53 does? To handle VLANs in hardware.

-- 
Rafał
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