Re: Synopsys Ethernet QoS Driver

From: Giuseppe CAVALLARO
Date: Mon Nov 21 2016 - 09:27:34 EST

On 11/21/2016 2:28 PM, Lars Persson wrote:

21 nov. 2016 kl. 13:53 skrev Giuseppe CAVALLARO <peppe.cavallaro@xxxxxx>:

Hello Joao

On 11/21/2016 1:32 PM, Joao Pinto wrote:

On 21-11-2016 05:29, Rayagond Kokatanur wrote:
On Sat, Nov 19, 2016 at 7:26 PM, Rabin Vincent <rabin@xxxxxx> 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:


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).


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.

Thanks Lars, I will be happy to support all you on this transition
and I agree on renaming all.


- Lars


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?