netdev - Re: [PATCH net-next] net: phy: Trigger state machine on state change and not polling.

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Date:   Wed, 12 Oct 2016 16:44:31 -0500
From:   Kyle Roeschley <kyle.roeschley@...com>
To:     Andrew Lunn <andrew@...n.ch>
CC:     David Miller <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Florian Fainelli <f.fainelli@...il.com>
Subject: Re: [PATCH net-next] net: phy: Trigger state machine on state change
 and not polling.

On Wed, Oct 12, 2016 at 10:14:53PM +0200, Andrew Lunn wrote:
> The phy_start() is used to indicate the PHY is now ready to do its
> work. The state is changed, normally to PHY_UP which means that both
> the MAC and the PHY are ready.
> 
> If the phy driver is using polling, when the next poll happens, the
> state machine notices the PHY is now in PHY_UP, and kicks off
> auto-negotiation, if needed.
> 
> If however, the PHY is using interrupts, there is no polling. The phy
> is stuck in PHY_UP until the next interrupt comes along. And there is
> no reason for the PHY to interrupt.
> 
> Have phy_start() schedule the state machine to run, which both speeds
> up the polling use case, and makes the interrupt use case actually
> work.
> 
> This problems exists whenever there is a state change which will not
> cause an interrupt. Trigger the state machine in these cases,
> e.g. phy_error().
> 
> Signed-off-by: Andrew Lunn <andrew@...n.ch>
> Cc: Kyle Roeschley <kyle.roeschley@...com>
> ---
> 
> This should be applied to stable, but i've no idea what fixes: tag to
> use. It could be phylib has been broken since interrupts were added?
> 

This patched fixed another problem had with the phy state machine which was
caused by d5c3d8465 ("net: phy: Avoid polling PHY with PHY_IGNORE_INTERRUPTS").
That might be the commit you're looking for. Also,

Tested-by: Kyle Roeschley <kyle.roeschley@...com>

>  drivers/net/phy/phy.c | 22 ++++++++++++++++++++--
>  1 file changed, 20 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/phy/phy.c b/drivers/net/phy/phy.c
> index c6f66832a1a6..f424b867f73e 100644
> --- a/drivers/net/phy/phy.c
> +++ b/drivers/net/phy/phy.c
> @@ -608,6 +608,21 @@ void phy_start_machine(struct phy_device *phydev)
>  }
>  
>  /**
> + * phy_trigger_machine - trigger the state machine to run
> + *
> + * @phydev: the phy_device struct
> + *
> + * Description: There has been a change in state which requires that the
> + *   state machine runs.
> + */
> +

You've got a bonus newline here.

> +static void phy_trigger_machine(struct phy_device *phydev)
> +{
> +	cancel_delayed_work_sync(&phydev->state_queue);
> +	queue_delayed_work(system_power_efficient_wq, &phydev->state_queue, 0);
> +}
> +
> +/**
>   * phy_stop_machine - stop the PHY state machine tracking
>   * @phydev: target phy_device struct
>   *
> @@ -639,6 +654,8 @@ static void phy_error(struct phy_device *phydev)
>  	mutex_lock(&phydev->lock);
>  	phydev->state = PHY_HALTED;
>  	mutex_unlock(&phydev->lock);
> +
> +	phy_trigger_machine(phydev);
>  }
>  
>  /**
> @@ -800,8 +817,7 @@ void phy_change(struct work_struct *work)
>  	}
>  
>  	/* reschedule state queue work to run as soon as possible */
> -	cancel_delayed_work_sync(&phydev->state_queue);
> -	queue_delayed_work(system_power_efficient_wq, &phydev->state_queue, 0);
> +	phy_trigger_machine(phydev);
>  	return;
>  
>  ignore:
> @@ -890,6 +906,8 @@ void phy_start(struct phy_device *phydev)
>  	/* if phy was suspended, bring the physical link up again */
>  	if (do_resume)
>  		phy_resume(phydev);
> +
> +	phy_trigger_machine(phydev);
>  }
>  EXPORT_SYMBOL(phy_start);
>  
> -- 
> 2.9.3
> 

-- 
Kyle Roeschley
Software Engineer
National Instruments