linux-kernel - Re: [PATCH net-next 5/7] net: phy: marvell10g: Force reading of 2.5/5G PMA extended abilities

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Message-ID: <20190121132945.6e6dee23@bootlin.com>
Date:   Mon, 21 Jan 2019 13:29:45 +0100
From:   Maxime Chevallier <maxime.chevallier@...tlin.com>
To:     Russell King - ARM Linux admin <linux@...linux.org.uk>
Cc:     Andrew Lunn <andrew@...n.ch>, davem@...emloft.net,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Florian Fainelli <f.fainelli@...il.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        linux-arm-kernel@...ts.infradead.org,
        Antoine Tenart <antoine.tenart@...tlin.com>,
        thomas.petazzoni@...tlin.com, gregory.clement@...tlin.com,
        miquel.raynal@...tlin.com, nadavh@...vell.com, stefanc@...vell.com,
        mw@...ihalf.com
Subject: Re: [PATCH net-next 5/7] net: phy: marvell10g: Force reading of
 2.5/5G PMA extended abilities

Hello Russell,

On Mon, 21 Jan 2019 10:52:06 +0000
Russell King - ARM Linux admin <linux@...linux.org.uk> wrote:

>On Mon, Jan 21, 2019 at 11:35:31AM +0100, Maxime Chevallier wrote:
>> Hello Andrew,
>> 
>> On Sun, 20 Jan 2019 20:08:09 +0100
>> Andrew Lunn <andrew@...n.ch> wrote:
>>   
>> >On Fri, Jan 18, 2019 at 04:23:50PM +0100, Maxime Chevallier wrote:  
>> >> As per 802.3bz, if bit 14 of (1.11) "PMA Extended Abilities" indicates
>> >> whether or not we should read register (1.21) "2.52/5G PMA Extended
>> >> Abilities", which contains information on the support of 2.5GBASET and
>> >> 5GBASET.
>> >> 
>> >> After testing on several variants of PHYS of this family, it appears
>> >> that bit 14 in (1.11) isn't always set when it should be.
>> >> 
>> >> PHYs 88X3310 (on MacchiatoBin) and 88E2010 do support 2.5G and 5GBASET,
>> >> but don't have 1.11.14 set. Their register 1.21 is filled with the
>> >> correct values, indicating 2.5G and 5G support.
>> >> 
>> >> PHYs 88X2110 do have their 1.11.14 bit set, as it should.    
>> >
>> >Hi Maxime
>> >
>> >Is there anything about this in any Errata?  
>> 
>> I haven't seen any Errata on that unfortunately.
>> 
>> I also thought about reading (1.4) "PMA/PMD Speed Ability", but the
>> 2.5G and 5G speeds are also reported as not being supported on the
>> 88X3310.  
>
>It's entirely possible that the 3310 switches to different hardware
>blocks for 2.5G and 5G speeds, and reading _just_ the 1.4 register
>is not sufficient.

I agree with you but in that particular case, I think we are reading
from the correct device. The datasheet itself says that we should be
reading 1.4 and 1.11 as we expect, with 2.5G/5G support being set (these
registers are read-only, and the datasheet's values aren't what we
actually read).

>The 88x3310 is multiple PHY devices in one package, with a CPU that
>manages the routing between each individual device.

I also just checked register 3.4 "PCS Speed Ability", and 3.8 "PCS
Status 2" which also contains informations on 2.5G/5G abilities, but
there's the same issue here.

Maxime

-- 
Maxime Chevallier, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com