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Date:   Mon, 28 Jun 2021 12:57:42 +0300
From:   Cristian Ciocaltea <cristian.ciocaltea@gmail.com>
To:     Amit Tomer <amittomer25@gmail.com>
Cc:     Florian Fainelli <f.fainelli@gmail.com>,
        "David S. Miller" <davem@davemloft.net>,
        Andrew Lunn <andrew@lunn.ch>, Jakub Kicinski <kuba@kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Andreas =?iso-8859-1?Q?F=E4rber?= <afaerber@suse.de>,
        Manivannan Sadhasivam <mani@kernel.org>,
        Philipp Zabel <p.zabel@pengutronix.de>, netdev@vger.kernel.org,
        devicetree@vger.kernel.org,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
        linux-actions@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 2/3] net: ethernet: actions: Add Actions Semi Owl
 Ethernet MAC driver
Message-ID: <20210628095742.GA2261718@BV030612LT>
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Hi Amit,

On Mon, Jun 28, 2021 at 01:55:40PM +0530, Amit Tomer wrote:
> Hi,
> 
> > > Do you know the story behind this Ethernet controller?
> >
> > I just happened to get a board based on the S500 SoC, so I took this
> > opportunity to help improving the mainline kernel support, but other
> > than that I do not really know much about the hardware history.
> >
> > > The various
> > > receive/transmit descriptor definitions are 99% those defined in
> > > drivers/net/ethernet/stmmicro/stmmac/descs.h for the normal descriptor.
> >
> > That's an interesting observation. I could only assume the vendor did
> > not want to reinvent the wheel here, but I cannot say if this is a
> > common design scheme or is something specific to STMicroelectronics
> > only.
> 
> I am not entirely sure about it but it looks like it *may* only need
> to have a glue driver to
> connect to DWMAC.

From the RX/TX descriptors perspective, this looks like a Synopsys IP,
but the MAC register layout is not similar at all.

Thanks to Mani, a request for clarification has been also sent to Actions,
but they could not confirm. Hence, at the moment, we do not have clear
evidences that it is based on Designware.

> For instance, on the U-boot[1] side (S700 is one of 64bit OWL SoC from
> actions), we kind of re-uses already
> existing DWMAC and provide a glue code, and on the Linux side as well
> have some similar implementation (locally).

The S700 SoC provides Gigabit ethernet capabilities and I assume the
controller is quite different from the 10/100 variant present on S500.
As a matter of fact, Actions has confirmed that in the case of S700, the
licensing was obtained from a third party IP company, although they were
not certain if the provider had previous agreements with Synopsys.

Regards,
Cristi

> Thanks
> -Amit.
> 
> [1]: https://source.denx.de/u-boot/u-boot/-/blob/master/drivers/net/dwmac_s700.c