linux-kernel - Re: Synopsys Ethernet QoS Driver

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Message-ID: <BFA799B0-BB22-4515-AC14-3544A3167B0A@axis.com>
Date:   Mon, 21 Nov 2016 13:28:36 +0000
From:   Lars Persson <lars.persson@...s.com>
To:     Giuseppe CAVALLARO <peppe.cavallaro@...com>
CC:     Joao Pinto <Joao.Pinto@...opsys.com>,
        Rayagond Kokatanur <rayagond@...avyalabs.com>,
        Rabin Vincent <rabin@....in>, mued dib <kreptor@...il.com>,
        David Miller <davem@...emloft.net>,
        Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
        "jiri@...lanox.com" <jiri@...lanox.com>,
        "saeedm@...lanox.com" <saeedm@...lanox.com>,
        "idosch@...lanox.com" <idosch@...lanox.com>,
        netdev <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "CARLOS.PALMINHA@...opsys.com" <CARLOS.PALMINHA@...opsys.com>,
        Andreas Irestål <andire@...s.com>,
        "alexandre.torgue@...com" <alexandre.torgue@...com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: Synopsys Ethernet QoS Driver



> 21 nov. 2016 kl. 13:53 skrev Giuseppe CAVALLARO <peppe.cavallaro@...com>:
> 
> 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.
> 
> It also supports QoS hardware; for example, 4.00a, 4.10a and 4.20a
> are fully working.
> 
> 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.
> 
> 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.
> 
> 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
> 

Hello Joao and others,

As the maintainer of dwc_eth_qos.c I prefer also that we put efforts on the most mature driver, the stmmac.

I hope that the code can migrate into an ethernet/synopsys folder to keep the convention of naming the folder after the vendor. This makes it easy for others to find the driver. 

The dwc_eth_qos.c will eventually be removed and its DT binding interface can then be implemented in the stmmac driver.

- Lars

>> 
>> 
>>> 
>>>> 
>>>> (See http://lists.openwall.net/netdev/2016/02/29/127)
>>>> 
>>>> The former only supports 4.x of the hardware.
>>>> 
>>>> The later supports 4.x and 3.x and already has a platform glue driver
>>>> with support for several platforms, a PCI glue driver, and a core driver
>>>> with several features not present in the former (for example: TX/RX
>>>> interrupt coalescing, EEE, PTP).
>>>> 
>>>> Have you evaluated both drivers?  Why have you decided to work on the
>>>> former rather than the latter?
>>> 
>>> 
>> 
>> Thanks.
>> 
>> 
>> 
>> 
>