linux-kernel - Re: [PATCH v3 1/2] net: phy: Fix PHY AN done state machine for interrupt driven PHYs

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Message-ID: <42a72e93-8c10-a4b3-8c0f-d3350fc5e2c1@gmail.com>
Date:   Wed, 19 Apr 2017 09:28:00 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Roger Quadros <rogerq@...com>, andrew@...n.ch
Cc:     davem@...emloft.net, kyle.roeschley@...com, nsekhar@...com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        "stable # v4 . 9+" <stable@...r.kernel.org>,
        Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
        "Andrew F. Davis" <afd@...com>,
        Alexander Kochetkov <al.kochet@...il.com>
Subject: Re: [PATCH v3 1/2] net: phy: Fix PHY AN done state machine for
 interrupt driven PHYs

On 04/11/2017 04:17 AM, Roger Quadros wrote:
> Hi,
> 
> On 28/03/17 13:05, Roger Quadros wrote:
>> +Andrew Davis & Sekhar.
>>
>> Hi,
>>
>> Andrew Davis posted a few comments offline which I'm clarifying here.
>>
>> On 27/03/17 14:59, Roger Quadros wrote:
>>> The Ethernet link on an interrupt driven PHY was not coming up if the
>>> Ethernet cable was plugged before the Ethernet interface was brought up.
>>>
>>> The PHY state machine seems to be stuck from RUNNING to AN state
>>> with no new interrupts from the PHY. So it doesn't know when the
>>> PHY Auto-negotiation has been completed and doesn't transition to RUNNING
>>> state with ANEG done thus netif_carrier_on() is never called.
>>>
>>> NOTE: genphy_config_aneg() will not restart PHY Auto-negotiation of
>>> advertisement parameters didn't change.
>>
>> Is phy->config_aneg expected to *always* restart auto-negotiation even if
>> advertisement parameters didn't change?
>> If so then we'll need to fix genphy_config_aneg().
>>
>>>
>>> Fix this by scheduling the PHY state machine in phy_start_aneg().
>>> There is no way of knowing in phy.c whether auto-negotiation was
>>> restarted or not by the PHY driver so we just wait for the next
>>> poll/interrupt to update the PHY state machine.
>>>
>>> Fixes: 3c293f4e08b5 ("net: phy: Trigger state machine on state change and not polling.")
>>> Cc: stable <stable@...r.kernel.org> # v4.9+
>>> Signed-off-by: Roger Quadros <rogerq@...com>
>>> ---
>>> v3: Fix typo in commit message
>>>
>>>  drivers/net/phy/phy.c | 4 ++++
>>>  1 file changed, 4 insertions(+)
>>>
>>> diff --git a/drivers/net/phy/phy.c b/drivers/net/phy/phy.c
>>> index 1be69d8..49dedf8 100644
>>> --- a/drivers/net/phy/phy.c
>>> +++ b/drivers/net/phy/phy.c
>>> @@ -630,6 +630,10 @@ int phy_start_aneg(struct phy_device *phydev)
>>>  
>>>  out_unlock:
>>>  	mutex_unlock(&phydev->lock);
>>> +	if (!err && phy_interrupt_is_valid(phydev))
>>> +		queue_delayed_work(system_power_efficient_wq,
>>> +				   &phydev->state_queue, HZ);
>>> +
>>>  	return err;
>>>  }
>>>  EXPORT_SYMBOL(phy_start_aneg);
>>>
>>
>> There is still room for optimization for interrupt driven PHYs as I still
>> see a delay of 1 second between "ifconfig ethx up" and link status coming up
>> if cable was already plugged in. In fact if Auto-negotiation was already completed
>> and not required to be restarted, the PHY state machine should have move from
>> AN to RUNNING instantly without expecting a PHY interrupt.
>>
>> How can we get rid of the unnecessary delay in the case where auto-negotiation
>> is not restarted?
>> Should we check for phy_aneg_done() immediately after issuing a phy_start_aneg()
>> in phy_state_machine() and switch from PHY_AN to PHY_RUNNING?

That sounds like a good idea yes. It seems to me like Alexander's patch
actually takes care of that:

http://patchwork.ozlabs.org/patch/752288/

Let's try to merge threads/recipients so we can shoot for a fix to be
included soon.

Thanks!

>>
>> This should avoid the need to re-schedule the state machine in phy_start_angeg().
> 
> Any comments on my questions?
> 
> cheers,
> -roger
> 


-- 
Florian