linux-kernel - RE: [RFC PATCH] net: macb: Add gmii2rgmii converter support

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Date:	Mon, 20 Jun 2016 06:15:32 +0000
From:	Appana Durga Kedareswara Rao <appana.durga.rao@...inx.com>
To:	Florian Fainelli <f.fainelli@...il.com>,
	"nicolas.ferre@...el.com" <nicolas.ferre@...el.com>,
	Punnaiah Choudary Kalluri <punnaia@...inx.com>,
	Harini Katakam <harinik@...inx.com>,
	Anirudha Sarangi <anirudh@...inx.com>,
	Michal Simek <michals@...inx.com>
CC:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Andrew Lunn <andrew@...n.ch>
Subject: RE: [RFC PATCH] net: macb: Add gmii2rgmii converter support

Hi Florian,

	Thanks for the quick response...

> 
> On June 19, 2016 10:27:17 PM MST, Kedareswara rao Appana
> <appana.durga.rao@...inx.com> wrote:
> >This patch adds support for gmii2rgmii converter in the macb driver.
> >
> >The GMII to RGMII IP core provides the
> >Reduced Gigabit Media Independent Interface
> >(RGMII) between Ethernet physical media devices And the Gigabit
> >Ethernet controller.
> >This core can switch dynamically between the Three different speed
> >modes of operation (10/100/1000 Mb/s).
> >MDIO interface is used to set operating speed of Ethernet MAC.
> >
> >Signed-off-by: Kedareswara rao Appana <appanad@...inx.com>
> >---
> >--> Tried to include this Coverter support in the
> >PHY layer but it won't fit into the PHY framework as the coverter won't
> >have vaild vendor/Device id registers.
> >--> The Converter has only one register (16) that need's
> >to be programmed with the external phy negotiated speed.
> >--> The converter won't follow the Standard MII(ieee 802.3 clause 22).
> >--> Will appreciate if someone can help on adding this coverter support
> 
> With the fixed PHY emulated PHY and registering a link_update callback (see
> drivers/net/dsa/bcm_sf2.c for an example), you could read specific registers
> which indicates link parameters and update the PHY device with these.

Thanks will check and get back...

> 
> How exactly is this converter working?

This converter does GMII to RGMII conversion. 
It provides only one register for programing the desired speed and MDIO is Interface to program this register.
It sits between the mac and external phy. So, once the phy negotiation completes and link is up,
The negotiated speed should be programmed in the converter.

Converter data sheet:
http://www.xilinx.com/support/documentation/ip_documentation/gmii_to_rgmii/v3_0/pg160-gmii-to-rgmii.pdf

Regards,
Kedar.

> 
> --
> Florian