On 29/07/2024 11:47, Russell King (Oracle) wrote: ...
Apologies for not following up before on this and now that is has been a year I am not sure if it is even appropriate to dig this up as opposed to starting a new thread completely. However, I want to resume this conversation because we have found that this change does resolve a long-standing issue where we occasionally see our ethernet controller fail to get an IP address. I understand that your objection to the above change is that (per Revanth's feedback) this change assumes interface has the link. However, looking at the aqr107_read_status() function where this change is made the function has the following ... static int aqr107_read_status(struct phy_device *phydev) { int val, ret; ret = aqr_read_status(phydev); if (ret) return ret; if (!phydev->link || phydev->autoneg == AUTONEG_DISABLE) return 0; So my understanding is that if we don't have the link, then the above test will return before we attempt to poll the TX ready status. If that is the case, then would the change being proposed be OK?Here, phydev->link will be the _media_ side link. This is fine - if the media link is down, there's no point doing anything further. However, if the link is up, then we need the PHY to update phydev->interface _and_ report that the link was up (phydev->link is true). When that happens, the layers above (e.g. phylib, phylink, MAC driver) then know that the _media_ side interface has come up, and they also know the parameters that were negotiated. They also know what interface mode the PHY is wanting to use. At that point, the MAC driver can then reconfigure its PHY facing interface according to what the PHY is using. Until that point, there is a very real chance that the PHY <--> MAC connection will remain _down_. The patch adds up to a _two_ _second_ wait for the PHY <--> MAC connection to come up before aqr107_read_status() will return. This is total nonsense - because waiting here means that the MAC won't get the notification of which interface mode the PHY is expecting to use, therefore the MAC won't configure its PHY facing hardware for that interface mode, and therefore the PHY <--> MAC connection will _not_ _come_ _up_. You can not wait for the PHY <--> MAC connection to come up in the phylib read_status method. Ever. This is non-negotiable because it is just totally wrong to do this and leads to pointless two second delays.
Thanks for the feedback! We will go away, review this and see if we can figure out a good/correct way to resolve our ethernet issue.
Jon -- nvpublic
