linux-kernel - Re: [PATCH net 2/2] net: phy: Use C45 Helpers in PHY

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Date:   Mon, 4 Mar 2019 19:10:28 +0100
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Andrew Lunn <andrew@...n.ch>, Jose Abreu <jose.abreu@...opsys.com>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Joao Pinto <joao.pinto@...opsys.com>
Subject: Re: [PATCH net 2/2] net: phy: Use C45 Helpers in PHY_FORCING state

On 04.03.2019 16:44, Andrew Lunn wrote:
> On Mon, Mar 04, 2019 at 03:07:24PM +0000, Jose Abreu wrote:
>> Hi Andrew,
>>
>> On 3/1/2019 1:53 PM, Andrew Lunn wrote:
>>> On Fri, Mar 01, 2019 at 11:54:24AM +0100, Jose Abreu wrote:
>>>> +static inline int phy_update_link(struct phy_device *phydev)
>>>> +{
>>>> +	if (!phydev->drv)
>>>> +		return -EIO;
>>>> +
>>>> +	if (phydev->drv->read_status)
>>>> +		return phydev->drv->read_status(phydev);
>>>> +	else if (phydev->is_c45)
>>>> +		return gen10g_read_status(phydev);
>>>> +	else
>>>> +		return genphy_update_link(phydev);
>>>> +}
>>>
>>> Hi Jose
>>>
>>> The asymmetry here could be an issue.  We might fall into the trap
>>> that a c45 PHY has the full state in phydev updated, were as a c22
>>> only has the link updated. Somebody testing on C45 might miss a bug
>>> for a C22 device.
>>
>> Notice that this phy_update_link() is called from PHY_FORCING
>> state which in my case happens when autoneg is not enabled / is
>> not supported.
>>
>> I think it makes sense, in this case, to only update link status,
>> no ?
>  
> Hi Jose
> 
> It is actually quite difficult to determine when the link is up. I
> personally would not trust gen10g_read_status() to get this right, and
> would always implement the read_status callback.
> 
Not to forget that we just stopped exporting gen10g_read_status().
genphy_c45_read_link() seems to be the right function to be used
in phy_update_link().

> Which PHY driver are you using, which does not support
> read_status(). All the mainline PHY drivers do seem to have
> read_status implemented.
> 
>     Andrew
> 
Heiner