linux-kernel - Re: [PATCH net-next v2 3/4] dt-bindings: net: Add RGMII internal delay for DP83869

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Message-ID: <95ab99bf-2fb5-c092-ad14-1b0a47c782a4@ti.com>
Date:   Wed, 20 May 2020 10:56:04 -0500
From:   Dan Murphy <dmurphy@...com>
To:     Andrew Lunn <andrew@...n.ch>
CC:     <f.fainelli@...il.com>, <hkallweit1@...il.com>,
        <davem@...emloft.net>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>
Subject: Re: [PATCH net-next v2 3/4] dt-bindings: net: Add RGMII internal
 delay for DP83869

Andrew

On 5/20/20 10:36 AM, Andrew Lunn wrote:
>>> Hi Dan
>>>
>>> Having it required with PHY_INTERFACE_MODE_RGMII_ID or
>>> PHY_INTERFACE_MODE_RGMII_RXID is pretty unusual. Normally these
>>> properties are used to fine tune the delay, if the default of 2ns does
>>> not work.
>> Also if the MAC phy-mode is configured with RGMII-ID and no internal delay
>> values defined wouldn't that be counter intuitive?
> Most PHYs don't allow the delay to be fine tuned. You just pass for
> example PHY_INTERFACE_MODE_RGMII_ID to the PHY driver and it enables a
> 2ns delay. That is what people expect, and is documented.

> Being able to tune the delay is an optional extra, which some PHYs
> support, but that is always above and beyond
> PHY_INTERFACE_MODE_RGMII_ID.

I am interested in knowing where that is documented.  I want to RTM I 
grepped for a few different words but came up empty

Since this is a tuneable phy we need to program the ID.  2ns is the 
default value

Maybe I can change it from Required to Configurable or Used.

Dan


>       Andrew