linux-kernel - Re: [PATCH v2 0/3] net: Add Keystone NetCP ethernet driver support

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Message-ID: <5411C005.10108@ti.com>
Date:	Thu, 11 Sep 2014 11:30:13 -0400
From:	Santosh Shilimkar <santosh.shilimkar@...com>
To:	Jamal Hadi Salim <jhs@...atatu.com>,
	David Miller <davem@...emloft.net>
CC:	<netdev@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>, <robh+dt@...nel.org>,
	<grant.likely@...aro.org>, <devicetree@...r.kernel.org>,
	<sandeep_n@...com>, Benjamin LaHaise <bcrl@...ck.org>,
	shrijeet Mukherjee <shm@...ulusnetworks.com>
Subject: Re: [PATCH v2 0/3] net: Add Keystone NetCP ethernet driver support

On Wednesday 10 September 2014 07:33 AM, Jamal Hadi Salim wrote:
> On 09/09/14 11:19, Santosh Shilimkar wrote:
> 
>> All the documentation is open including packet accelerator offload
>> in ti.com.
> 
> Very nice.
> Would you do me a kindness and point to the switch interface
> documentation (and other ones on that soc)?
>
You can find it here [1], [2], [3]

>> We got such requests from customers but couldn't
>> support it for Linux.
> 
> It has been difficult because every chip vendor is trying
> to do their own thing. Some have huge (fugly) SDKs in user space
> which make it worse. Thats the struggle we are trying to
> deal with. Of course none of those vendors want to open
> up their specs. You present a nice opportunity to not follow
> that path.
> 
>> We are also looking for such
>> support and any direction are welcome. Your slide
>> deck seems to capture the key topics like L2/IPSEC
>> offload which we are also interested to hear.
>>
> 
> The slides list the most popular offloads. But not necessarily
> all known offloads.
> 
>> Just to be clear, your point was about L2 switch offload
>> which the driver don't support at the moment. It might confuse
>> others. The driver doesn't implements anything non-standard.
>>
> 
> If i understood you correctly:
> Your initial patches dont intend to expose any offloads - you are just
> abstracting this as a NIC. I think that is a legit reason.
Yes. The NetCP hardware is abstracted as a regular NIC.

> However, the problem is you are also exposing the packet processors
> and switch offloading in a proprietary way.
> For a sample of how L2 basic functions like FDB tables are controlled
> within a NIC - take a look at the Intel NICs.
> Either that or you hide all the offload interfaces and over time add
> them (starting with L2 - NICs with L2 are common).
>
Switch offload isn't supported but we do agree that for packet
accelerator, we are using custom hooks because of lack of other
mechanism.

We will definitely use the new ndo based fdb offload scheme when
we get to it. We understand that the forward direction is to
have ndo operation based offloads and its the right way probably.

We will update the patch and drop all the custom exports. Anyway
the current driver doesn't support any offloads now. We can add
support for it as the frameworks evolves.

Thanks a lot for informative discussion and those links.

Regards,
Santosh
[1] http://www.ti.com/lit/pdf/sprugv9
[2] http://www.ti.com/lit/pdf/spruhj5
[3] http://www.ti.com/lit/pdf/sprugs4


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