linux-kernel - Re: [PATCH 1/3] ARM: dts: NSP: Enable SFP on bcm958625hr

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Message-ID: <455621d9-5021-5d54-12d6-661dfe152bde@gmail.com>
Date:   Mon, 27 Aug 2018 14:09:20 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     linux-arm-kernel@...ts.infradead.org,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Ray Jui <rjui@...adcom.com>,
        Scott Branden <sbranden@...adcom.com>,
        Jon Mason <jonmason@...adcom.com>,
        "maintainer:BROADCOM IPROC ARM ARCHITECTURE" 
        <bcm-kernel-feedback-list@...adcom.com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        rmk+kernel@...linux.org.uk
Subject: Re: [PATCH 1/3] ARM: dts: NSP: Enable SFP on bcm958625hr

On 08/27/2018 01:52 PM, Florian Fainelli wrote:
> On 08/27/2018 01:35 PM, Andrew Lunn wrote:
>>> @@ -210,6 +228,17 @@
>>>  			reg = <4>;
>>>  		};
>>>  
>>> +		port@5 {
>>> +			label = "sfp";
>>> +			phy-mode = "sgmii";
>>> +			reg = <5>;
>>> +			sfp = <&sfp>;
>>> +			fixed-link {
>>> +				speed = <1000>;
>>> +				full-duplex;
>>> +			};
>>
>> Hi Florian
>>
>> You might want to add a comment about why you are using fixed-link and
>> sgmii, which seems very odd. Is it even correct?
> 
> Probably not, this is kind of left over from before adding the sfp
> phandle, but if I do remove it, and I can see the DSA slave network
> device fail to initialize, likely because we destroy the PHYLINK instance.
> 
> AFAIR, when we talked about this with Russell, I did not see why we had
> to comment out the following:
> 
> diff --git a/net/dsa/slave.c b/net/dsa/slave.c
> index 962c4fd338ba..f3ae16dbf8d8 100644
> --- a/net/dsa/slave.c
> +++ b/net/dsa/slave.c
> @@ -1227,7 +1227,7 @@ static int dsa_slave_phy_setup(struct net_device
> *slave_dev)
>                         netdev_err(slave_dev,
>                                    "failed to connect to port %d: %d\n",
>                                    dp->index, ret);
> -                       phylink_destroy(dp->pl);
> +                       //phylink_destroy(dp->pl);
>                         return ret;
>                 }
>         }
> 
> maybe you know?

Stupid question, if we have a "sfp" phandle, must one also specify a
managed = "in-band-status" property? Under what circumstances are not
these two things implying one another (SFF maybe)?

That would explain why the code path taken from phylink_of_phy_connect()
would not return 0 and we would indeed fail to connect to the built-in
DSA MDIO bus.
-- 
Florian