netdev - Re: [EXTERNAL] Re: [PATCH v3 1/2] dt-bindings: net: Add ICSSG Ethernet Driver bindings

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Date:   Mon, 30 Jan 2023 12:32:53 +0530
From:   Md Danish Anwar <a0501179@...com>
To:     Roger Quadros <rogerq@...nel.org>, Andrew Lunn <andrew@...n.ch>,
        "Md Danish Anwar" <danishanwar@...com>
CC:     "Andrew F. Davis" <afd@...com>, Tero Kristo <t-kristo@...com>,
        Suman Anna <s-anna@...com>, YueHaibing <yuehaibing@...wei.com>,
        Vignesh Raghavendra <vigneshr@...com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        "Jakub Kicinski" <kuba@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        "David S. Miller" <davem@...emloft.net>, <nm@...com>,
        <ssantosh@...nel.org>, <srk@...com>,
        <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <netdev@...r.kernel.org>, <linux-omap@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [EXTERNAL] Re: [PATCH v3 1/2] dt-bindings: net: Add ICSSG
 Ethernet Driver bindings

Hi Roger,

On 05/01/23 17:03, Roger Quadros wrote:
> On 02/01/2023 20:34, Andrew Lunn wrote:
>> On Mon, Jan 02, 2023 at 03:04:19PM +0200, Roger Quadros wrote:
>>>
>>>
>>> On 23/12/2022 16:28, Andrew Lunn wrote:
>>>>> +        ethernet-ports {
>>>>> +            #address-cells = <1>;
>>>>> +            #size-cells = <0>;
>>>>> +            pruss2_emac0: port@0 {
>>>>> +                reg = <0>;
>>>>> +                phy-handle = <&pruss2_eth0_phy>;
>>>>> +                phy-mode = "rgmii-rxid";
>>>>
>>>> That is unusual. Where are the TX delays coming from?
>>>
>>> >From the below property
>>>
>>> +                ti,syscon-rgmii-delay = <&scm_conf 0x4120>;
>>>
>>> The TX delay can be enabled/disabled from within the ICSSG block.
>>>
>>> If this property exists and PHY mode is neither PHY_INTERFACE_MODE_RGMII_ID
>>> nor PHY_INTERFACE_MODE_RGMII_TXID then the internal delay is enabled.
>>>
>>> This logic is in prueth_config_rgmiidelay() function in the introduced driver.
>>
>> What nearly every other MAC driver does is pass the phy-mode to the
>> PHY and lets the PHY add the delays. I would recommend you do that,
>> rather than be special and different.
> 
> 
> If I remember right we couldn't disable MAC TX delay on some earlier silicon
> so had to take this route. I don't remember why we couldn't disable it though.
> 
> In more recent Silicon Manuals I do see that MAC TX delay can be enabled/disabled.
> If this really is the case then we should change to
> 
>  phy-mode = "rgmii-id";
> 
> And let PHY handle the TX+RX delays.
> 
> Danish,
> could you please make the change and test if it works on current silicon?
> 

I changed the phy-mode to "rgmii-id" instead of "rgmii-rxid". I did the testing
on current silicon (AM654x SR 2.0) and it is working fine.

> cheers,
> -roger

Thanks and Regards,
Danish.