linux-kernel - Re: [PATCH 06/16] net: phy: adin: support PHY mode converters

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Message-ID: <15cf5732415c313a7bfe610e7039e7c97b987073.camel@analog.com>
Date:   Tue, 6 Aug 2019 06:47:08 +0000
From:   "Ardelean, Alexandru" <alexandru.Ardelean@...log.com>
To:     "andrew@...n.ch" <andrew@...n.ch>
CC:     "davem@...emloft.net" <davem@...emloft.net>,
        "hkallweit1@...il.com" <hkallweit1@...il.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "f.fainelli@...il.com" <f.fainelli@...il.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>
Subject: Re: [PATCH 06/16] net: phy: adin: support PHY mode converters

On Mon, 2019-08-05 at 16:51 +0200, Andrew Lunn wrote:
> [External]
> 
> On Mon, Aug 05, 2019 at 07:54:43PM +0300, Alexandru Ardelean wrote:
> > Sometimes, the connection between a MAC and PHY is done via a
> > mode/interface converter. An example is a GMII-to-RGMII converter, which
> > would mean that the MAC operates in GMII mode while the PHY operates in
> > RGMII. In this case there is a discrepancy between what the MAC expects &
> > what the PHY expects and both need to be configured in their respective
> > modes.
> > 
> > Sometimes, this converter is specified via a board/system configuration (in
> > the device-tree for example). But, other times it can be left unspecified.
> > The use of these converters is common in boards that have FPGA on them.
> > 
> > This patch also adds support for a `adi,phy-mode-internal` property that
> > can be used in these (implicit convert) cases. The internal PHY mode will
> > be used to specify the correct register settings for the PHY.
> > 
> > `fwnode_handle` is used, since this property may be specified via ACPI as
> > well in other setups, but testing has been done in DT context.
> 
> Looking at the patch, you seems to assume phy-mode is what the MAC is
> using? That seems rather odd, given the name. It seems like a better
> solution would be to add a mac-mode, which the MAC uses to configure
> its side of the link. The MAC driver would then implement this
> property.
> 

actually, that's a pretty good idea;
i guess i was narrow-minded when writing the driver, and got stuck on phy specifics, and forgot about the MAC-side;
[ i also catch these design elements when reviewing, but i also seem to miss them when writing stuff sometimes ]

thanks

> I don't see a need for this. phy-mode indicates what the PHY should
> use. End of story.
> 
>      Andrew