netdev - Re: [PATCH v2 02/15] net: phy: adin: hook genphy_read_abilities() to get

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Date:   Thu, 8 Aug 2019 21:32:57 +0200
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Andrew Lunn <andrew@...n.ch>,
        Alexandru Ardelean <alexandru.ardelean@...log.com>
Cc:     netdev@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, davem@...emloft.net,
        robh+dt@...nel.org, mark.rutland@....com, f.fainelli@...il.com
Subject: Re: [PATCH v2 02/15] net: phy: adin: hook genphy_read_abilities() to
 get_features

On 08.08.2019 17:24, Andrew Lunn wrote:
> On Thu, Aug 08, 2019 at 03:30:13PM +0300, Alexandru Ardelean wrote:
>> The ADIN PHYs can operate with Clause 45, however they are not typical for
>> how phylib considers Clause 45 PHYs.
>>
>> If the `features` field & the `get_features` hook are unspecified, and the
>> device wants to operate via Clause 45, it would also try to read features
>> via the `genphy_c45_pma_read_abilities()`, which will try to read PMA regs
>> that are unsupported.
>>
>> Hooking the `genphy_read_abilities()` function to the `get_features` hook
>> will ensure that this does not happen and the PHY features are read
>> correctly regardless of Clause 22 or Clause 45 operation.
> 
> I think we need to stop and think about a PHY which supports both C22
> and C45.
> 
> How does bus enumeration work? Is it discovered twice?  I've always
> considered phydev->is_c45 means everything is c45, not that some
> registers can be accessed via c45. But the driver is mixing c22 and
> c45. Does the driver actually require c45? Are some features which are
> only accessibly via C45? What does C45 actually bring us for this
> device?
> 
genphy_c45_pma_read_abilities() is only called if phydev->is_c45 is set.
And this flag means that the PHY complies with Clause 45 incl. all the
standard devices like PMA. In the case here only some vendor-specific
registers can be accessed via Clause 45 and therefore is_c45 shouldn't
bet set. As a consequence this patch isn't needed.

>      Andrew
> 
Heiner