linux-kernel - Re: [PATCH] net: phy: dp83867: Port mirroring support in the DP83867 TI's PHY driver

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Message-ID: <20170201220500.29d478aa@jawa>
Date:   Wed, 1 Feb 2017 22:05:00 +0100
From:   Lukasz Majewski <lukma@...x.de>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     Andrew Lunn <andrew@...n.ch>, Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        "David S. Miller" <davem@...emloft.net>,
        Mugunthan V N <mugunthanvnm@...com>,
        Karicheri Muralidharan <m-karicheri2@...com>,
        linux-kernel@...r.kernel.org, Eric Engestrom <eric@...estrom.ch>,
        netdev@...r.kernel.org, Kishon Vijay Abraham I <kishon@...com>,
        Grygorii Strashko <grygorii.strashko@...com>,
        devicetree@...r.kernel.org
Subject: Re: [PATCH] net: phy: dp83867: Port mirroring support in the
 DP83867 TI's PHY driver

Dear All,

Thanks for prompt reply.

> On 02/01/2017 09:16 AM, Andrew Lunn wrote:
> > On Wed, Feb 01, 2017 at 03:43:35PM +0100, Lukasz Majewski wrote:
> >> This patch adds support for enabling or disabling the port
> >> mirroring feature of the DP83867 TI's PHY device.
> >>
> >> One use case is when bootstrap configuration enables this feature
> >> (because of e.g. LED wiring) so then one needs to disable it in
> >> software (u-boot/Linux).
> > 
> > Hi Lukasz
> > 
> > How does this differ from "enet-phy-lane-swap"?
> 
> Same here, I am confused about what port mirroring could be meaning
> here

The "net-phy-lane-swap" when defined indicates that the "lane swap"
needs to be enabled. This is a simple bool variable. In my case it
would mean: "please enable port mirroring -> write 1 to CFG4 register's
PORT_MIRROR_EN field"

My use case is unfortunately different:

- Due to HW design - during the bootstrap PHY phase - the PHY enables
  "port mirroring", which is incorrect. 

Then, in SW I do need to explicitly disable port mirroring (write 0 to
PORT_MIRROR_EN field in CFG4 register). 


> and if we can find a better way to describe what is being added.
> Thanks!

We would need a tri-state device tree properly:

1. Not defined - do nothing
2. Defined as 0 -> explicitly disable port mirroring
3. Defined as 1 -> explicitly enable port mirriring

The "net-phy-lane-swap" only fulfills points 1 and 3 above.

In my use case I do need point 2.

Best regards,

Lukasz Majewski

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