Re: [PATCH net 2/2] net: phy: Check harder for errors in get_phy_id()

Florian Fainelli
2020-06-19T18:42:21Z

On 6/19/2020 6:30 AM, Russell King - ARM Linux admin wrote:
> On Fri, Jun 19, 2020 at 03:26:59PM +0200, Andrew Lunn wrote:
>> On Thu, Jun 18, 2020 at 09:47:59PM -0700, Florian Fainelli wrote:
>>> Commit 02a6efcab675 ("net: phy: allow scanning busses with missing
>>> phys") added a special condition to return -ENODEV in case -ENODEV or
>>> -EIO was returned from the first read of the MII_PHYSID1 register.
>>>
>>> In case the MDIO bus data line pull-up is not strong enough, the MDIO
>>> bus controller will not flag this as a read error. This can happen when
>>> a pluggable daughter card is not connected and weak internal pull-ups
>>> are used (since that is the only option, otherwise the pins are
>>> floating).
>>>
>>> The second read of MII_PHYSID2 will be correctly flagged an error
>>> though, but now we will return -EIO which will be treated as a hard
>>> error, thus preventing MDIO bus scanning loops to continue succesfully.
>>>
>>> Apply the same logic to both register reads, thus allowing the scanning
>>> logic to proceed.
>>
>> Hi Florian
>>
>> Maybe extend the kerneldoc for this function to document the return
>> values and there special meanings?
>
> You mean like the patch I sent yesterday?
>
>> BTW: Did you look at get_phy_c45_ids()? Is it using the correct return
>> value? Given the current work being done to extend scanning to C45,
>> maybe it needs reviewing for issues like this.
>
> And the updates I sent for this yesterday? ;)

When Russell's patches land, they will address this correctly and
because I did not want to introduce any conflicts, this is not addressed
by this two patch series.
--
Florian