linux-kernel - Re: Synopsys Ethernet QoS Driver

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Message-ID: <afc18eb0-4c11-9668-498d-982624c6de78@synopsys.com>
Date:   Mon, 21 Nov 2016 13:48:53 +0000
From:   Joao Pinto <Joao.Pinto@...opsys.com>
To:     Giuseppe CAVALLARO <peppe.cavallaro@...com>,
        Joao Pinto <Joao.Pinto@...opsys.com>,
        Rayagond Kokatanur <rayagond@...avyalabs.com>,
        Rabin Vincent <rabin@....in>
CC:     mued dib <kreptor@...il.com>, David Miller <davem@...emloft.net>,
        "Jeff Kirsher" <jeffrey.t.kirsher@...el.com>, <jiri@...lanox.com>,
        <saeedm@...lanox.com>, <idosch@...lanox.com>,
        netdev <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <CARLOS.PALMINHA@...opsys.com>, <andreas.irestal@...s.com>,
        <alexandre.torgue@...com>, <lars.persson@...s.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: Synopsys Ethernet QoS Driver

Hello Peppe,

On 21-11-2016 12:52, Giuseppe CAVALLARO wrote:
> Hello Joao
> 
> On 11/21/2016 1:32 PM, Joao Pinto wrote:
>> Hello,
>>
>> On 21-11-2016 05:29, Rayagond Kokatanur wrote:
>>> On Sat, Nov 19, 2016 at 7:26 PM, Rabin Vincent <rabin@....in> wrote:
>>>> On Fri, Nov 18, 2016 at 02:20:27PM +0000, Joao Pinto wrote:
>>>>> For now we are interesting in improving the synopsys QoS driver under
>>>>> /nect/ethernet/synopsys. For now the driver structure consists of a single
>>>>> file
>>>>> called dwc_eth_qos.c, containing synopsys ethernet qos common ops and platform
>>>>> related stuff.
>>>>>
>>>>> Our strategy would be:
>>>>>
>>>>> a) Implement a platform glue driver (dwc_eth_qos_pltfm.c)
>>>>> b) Implement a pci glue driver (dwc_eth_qos_pci.c)
>>>>> c) Implement a "core driver" (dwc_eth_qos.c) that would only have Ethernet QoS
>>>>> related stuff to be reused by the platform / pci drivers
>>>>> d) Add a set of features to the "core driver" that we have available
>>>>> internally
>>>>
>>>> Note that there are actually two drivers in mainline for this hardware:
>>>>
>>>>  drivers/net/ethernet/synopsis/
>>>>  drivers/net/ethernet/stmicro/stmmac/
>>>
>>> Yes the later driver (drivers/net/ethernet/stmicro/stmmac/) supports
>>> both 3.x and 4.x. It has glue layer for pci, platform, core etc,
>>> please refer this driver once before you start.
>>>
>>> You can start adding missing feature of 4.x in stmmac driver.
>>
>> Thanks you all for all the info.
>> Well, I think we are in a good position to organize the ethernet drivers
>> concerning Synopsys IPs.
>>
>> First of all, in my opinion, it does not make sense to have a ethernet/synopsis
>> (typo :)) when ethernet/stmicro is also for a synopsys IP. If we have another
>> vendor using the same IP it should be able to reuse the commonn operations. But
>> I would put that discussion for later :)
>>
>> For now I suggest that for we create ethernet/qos and create there a folder
>> called dwc (designware controller) where all the synopsys qos IP specific code
>> in order to be reused for example by ethernet/stmicro/stmmac/. We just have to
>> figure out a clean interface for "client drivers" like stmmac to interact with
>> the new qos driver.
>>
>> What do you think about this approach?
> 
> The stmmac drivers run since many years on several platforms
> (sh4, stm32, arm, x86, mips ...) and it supports an huge of amount of
> configurations starting from 3.1x to 3.7x databooks.

Great!

> 
> It also supports QoS hardware; for example, 4.00a, 4.10a and 4.20a
> are fully working.

Synopsys QoS IP is a separated hardware component, so it should be reusable by
all implementations using it and so have its own "core driver" and platform +
pci glue drivers. This is necessary for example in hardware validation, where
you prototype an IP and instantiate its drivers and test it.

Was there a strong reason to integrate QoS features directly in stmmac and not
in synopsys/dwc_eth_qos.*?

> 
> Also the stmmac has platform, device-tree and pcie supports and
> a lot of maintained glue-logic files.
> 
> It is fully documented inside the kernel tree.

Thanks for the information, I am going to check it out.

> 
> I am happy to have new enhancements from other developers.
> So, on my side, if you want to spend your time on improving it on your
> platforms please feel free to do it!
> 
> Concerning the stmicro/stmmac naming, these come from a really old
> story and have no issue to adopt new folder/file names.

Thank you for your availability!

> 
> I am also open to merge fixes and changes from ethernet/synopsis.
> I want to point you on some benchmarks made by Alex some months ago
> (IIRC) that showed an stmmac winner (due to the several optimizations
> analyzed and reviewed in this mailing list).
> 
> Peppe
> 

Thanks
Joao