Date:   Wed, 19 Dec 2018 10:32:54 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Heiner Kallweit <hkallweit1@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        David Miller <davem@...emloft.net>
Cc:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next 1/2] net: phy: make PHY_HALTED a transition state
 to PHY_READY

On 12/18/18 10:53 PM, Heiner Kallweit wrote:
> PHY_HALTED and PHY_READY both are non-started states and quite similar.
> Major difference is that phy_start() changes from PHY_HALTED to
> PHY_RESUMING which doesn't reconfigure aneg (what PHY_UP does).
> 
> There's no guarantee that PHY registers are completely untouched when
> waking up from power-down, e.g. after system suspend. Therefore it's
> safer to reconfigure aneg also when starting from PHY_HALTED. This can
> be achieved and state machine made simpler by making PHY_HALTED going
> to PHY_READY after having stopped everything. Then the only way up is
> over PHY_UP. Also let's warn in phy_start() if it's called from a
> state other than PHY_READY.
> As part of the change PHY_HALTED is renamed to PHY_HALT to reflect that
> it is a transition state.

Sorry for being uber nitpicky here, but a state machine is supposed to
contain.. state names, PHY_HALT is more of an action.

The PHY library is not particularly optimized at the moment to avoid
disrupting the link when there is not a need to, so if somehow the
register contents are lost because of a low power mode that the PHY has
entered, the PHY driver's resume function is responsible for bringing
things back online.

> 
> Signed-off-by: Heiner Kallweit <hkallweit1@...il.com>
> ---
>  drivers/net/phy/phy.c | 41 +++++++++++++++++------------------------
>  include/linux/phy.h   | 16 ++++++++--------
>  2 files changed, 25 insertions(+), 32 deletions(-)
> 
> diff --git a/drivers/net/phy/phy.c b/drivers/net/phy/phy.c
> index d33e7b3ca..2a69d947e 100644
> --- a/drivers/net/phy/phy.c
> +++ b/drivers/net/phy/phy.c
> @@ -47,12 +47,12 @@ static const char *phy_state_to_str(enum phy_state st)
>  	switch (st) {
>  	PHY_STATE_STR(DOWN)
>  	PHY_STATE_STR(READY)
> +	PHY_STATE_STR(HALT)
>  	PHY_STATE_STR(UP)
>  	PHY_STATE_STR(RUNNING)
>  	PHY_STATE_STR(NOLINK)
>  	PHY_STATE_STR(FORCING)
>  	PHY_STATE_STR(CHANGELINK)
> -	PHY_STATE_STR(HALTED)
>  	PHY_STATE_STR(RESUMING)
>  	}
>  
> @@ -733,7 +733,7 @@ static void phy_error(struct phy_device *phydev)
>  	WARN_ON(1);
>  
>  	mutex_lock(&phydev->lock);
> -	phydev->state = PHY_HALTED;
> +	phydev->state = PHY_HALT;
>  	mutex_unlock(&phydev->lock);
>  
>  	phy_trigger_machine(phydev);
> @@ -859,16 +859,11 @@ void phy_stop(struct phy_device *phydev)
>  	if (phy_interrupt_is_valid(phydev))
>  		phy_disable_interrupts(phydev);
>  
> -	phydev->state = PHY_HALTED;
> +	phydev->state = PHY_HALT;
>  
>  	mutex_unlock(&phydev->lock);
>  
>  	phy_state_machine(&phydev->state_queue.work);
> -
> -	/* Cannot call flush_scheduled_work() here as desired because
> -	 * of rtnl_lock(), but PHY_HALTED shall guarantee irq handler
> -	 * will not reenable interrupts.
> -	 */
>  }
>  EXPORT_SYMBOL(phy_stop);
>  
> @@ -888,29 +883,26 @@ void phy_start(struct phy_device *phydev)
>  
>  	mutex_lock(&phydev->lock);
>  
> -	switch (phydev->state) {
> -	case PHY_READY:
> -		phydev->state = PHY_UP;
> -		break;
> -	case PHY_HALTED:
> +	if (phydev->state == PHY_READY) {
>  		/* if phy was suspended, bring the physical link up again */
>  		__phy_resume(phydev);
>  
>  		/* make sure interrupts are re-enabled for the PHY */
>  		if (phy_interrupt_is_valid(phydev)) {
>  			err = phy_enable_interrupts(phydev);
> -			if (err < 0)
> -				break;
> +			if (err < 0) {
> +				WARN_ON(1);
> +				goto out;
> +			}
>  		}
> -
> -		phydev->state = PHY_RESUMING;
> -		break;
> -	default:
> -		break;
> +		phydev->state = PHY_UP;
> +		phy_trigger_machine(phydev);
> +	} else {
> +		WARN(1, "called from state %s\n",
> +		     phy_state_to_str(phydev->state));
>  	}
> +out:
>  	mutex_unlock(&phydev->lock);
> -
> -	phy_trigger_machine(phydev);
>  }
>  EXPORT_SYMBOL(phy_start);
>  
> @@ -962,12 +954,13 @@ void phy_state_machine(struct work_struct *work)
>  			phy_link_down(phydev, false);
>  		}
>  		break;
> -	case PHY_HALTED:
> +	case PHY_HALT:
>  		if (phydev->link) {
>  			phydev->link = 0;
>  			phy_link_down(phydev, true);
>  			do_suspend = true;
>  		}
> +		phydev->state = PHY_READY;
>  		break;
>  	}
>  
> @@ -990,7 +983,7 @@ void phy_state_machine(struct work_struct *work)
>  	 * PHY, if PHY_IGNORE_INTERRUPT is set, then we will be moving
>  	 * between states from phy_mac_interrupt().
>  	 *
> -	 * In state PHY_HALTED the PHY gets suspended, so rescheduling the
> +	 * In state PHY_HALT the PHY gets suspended, so rescheduling the
>  	 * state machine would be pointless and possibly error prone when
>  	 * called from phy_disconnect() synchronously.
>  	 */
> diff --git a/include/linux/phy.h b/include/linux/phy.h
> index da039f211..21e553f51 100644
> --- a/include/linux/phy.h
> +++ b/include/linux/phy.h
> @@ -288,38 +288,38 @@ struct phy_device *mdiobus_scan(struct mii_bus *bus, int addr);
>   *
>   * NOLINK: PHY is up, but not currently plugged in.
>   * - irq or timer will set RUNNING if link comes back
> - * - phy_stop moves to HALTED
> + * - phy_stop moves to HALT
>   *
>   * FORCING: PHY is being configured with forced settings
>   * - if link is up, move to RUNNING
>   * - If link is down, we drop to the next highest setting, and
>   *   retry (FORCING) after a timeout
> - * - phy_stop moves to HALTED
> + * - phy_stop moves to HALT
>   *
>   * RUNNING: PHY is currently up, running, and possibly sending
>   * and/or receiving packets
>   * - irq or timer will set NOLINK if link goes down
> - * - phy_stop moves to HALTED
> + * - phy_stop moves to HALT
>   *
>   * CHANGELINK: PHY experienced a change in link state
>   * - timer moves to RUNNING if link
>   * - timer moves to NOLINK if the link is down
> - * - phy_stop moves to HALTED
> + * - phy_stop moves to HALT
>   *
> - * HALTED: PHY is up, but no polling or interrupts are done. Or
> + * HALT: PHY is up, but no polling or interrupts are done. Or
>   * PHY is in an error state.
>   *
> - * - phy_start moves to RESUMING
> + * - moves to READY
>   *
>   * RESUMING: PHY was halted, but now wants to run again.
>   * - If we are forcing, or aneg is done, timer moves to RUNNING
>   * - If aneg is not done, timer moves to AN
> - * - phy_stop moves to HALTED
> + * - phy_stop moves to HALT
>   */
>  enum phy_state {
>  	PHY_DOWN = 0,
>  	PHY_READY,
> -	PHY_HALTED,
> +	PHY_HALT,
>  	PHY_UP,
>  	PHY_RUNNING,
>  	PHY_NOLINK,
> 


-- 
Florian

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