2014-04-24 22:53 GMT-07:00 Balakumaran Kannan [off-list ref]:

On Fri, Apr 25, 2014 at 12:23 AM, Florian Fainelli [off-list ref] wrote:

quoted

2014-04-23 19:52 GMT-07:00 Balakumaran Kannan [off-list ref]:

quoted

phy_state_machine should check whether auto-negotiatin is completed
before changing phydev->state from PHY_NOLINK to PHY_RUNNING. If
auto-negotiation is not completed phydev->state should be set to
PHY_AN.

I need some time to review this. Just out of curiosity, is this fixing
a bug you have encountered or was this found by state machine
inspection?

Actually I encountered a problem that Linux-3.4 sends Neighbor Solicitation (NS)
before hardware completes auto-negotiation. The driver being used for
my hardware
is smsc911x.

While investigation on this, I came to know that state of phydev
follows this sequence
PHY_READY --> PHY_UP (in phy_start)
PHY_UP --> PHY_AN (in phy_start_aneg called by phy_state_machine)
PHY_AN --> PHY_NOLINK (in phy_state_machine. Link is down)
PHY_NOLINK --> PHY_RUNNING (in phy_state_machine. Link becomes ready)

So I felt that the sequence of PHY_AN --> PHY_RUNNING while link is up and
PHY_NOLINK --> PHY_RUNNING are different. In the earlier case aneg completion
is taken into account but not in later.

I see, we should indeed go back to PHY_AN

But this patch doesn't fix my problem. I made the smsc driver's open function to
poll on phy_aneg_done until auto-negotiation completes.

Here I have a doubt.
 * Linux network initialization and phy_state_machine runs in separate threads.
 * And driver doesn't bother about state of phydev.
Is it correct?

That is correct, once your driver calls phy_start(), the PHY state
machine executes in the background within the context of a separate
workqueue.

Doesn't driver need to confirm phydev is ready(PHY_RUNNING) before
returning to kernel?

phy_start() really starts the PHY state machine, but does not block
until the PHY is in the PHY_RUNNING state, which is something that
might never happen if e.g: the cable is disconnected.

What really tells the network stack whether the link is ready, is when
the PHY state machine calls netif_carrier_on().
-- 
Florian