netdev - Re: [PATCH] net: phy: Trigger link_change_notify on PHY

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Date:   Tue, 5 Jan 2021 17:58:21 +0100
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Marek Vasut <marex@...x.de>, netdev@...r.kernel.org,
        Russell King - ARM Linux <linux@...linux.org.uk>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     Andrew Lunn <andrew@...n.ch>,
        "David S . Miller" <davem@...emloft.net>
Subject: Re: [PATCH] net: phy: Trigger link_change_notify on PHY_HALTED

On 05.01.2021 17:11, Marek Vasut wrote:
> In case the PHY transitions to PHY_HALTED state in phy_stop(), the
> link_change_notify callback is not triggered. That's because the
> phydev->state = PHY_HALTED in phy_stop() is assigned first, and
> phy_state_machine() is called afterward. For phy_state_machine(),
> no state transition happens, because old_state = PHY_HALTED and
> phy_dev->state = PHY_HALTED.
> 

There are a few formal issues with this patch:
- It misses a net/net-next annotation. If it's meant to be a fix,
  then the Fixes tag is missing. I just checked the existing
  link_change_notify handlers and nobody is interested in state
  transitions to PHY_HALTED. Therefore I think it's more of an
  improvement. However AFAICS net-next is still closed.

- The maintainers should be in To: and the list(s) on cc.
- Seems that Russell and Jakub are missing as maintainers.


> Signed-off-by: Marek Vasut <marex@...x.de>
> Cc: Andrew Lunn <andrew@...n.ch>
> Cc: David S. Miller <davem@...emloft.net>
> Cc: Heiner Kallweit <hkallweit1@...il.com>
> ---
>  drivers/net/phy/phy.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/net/phy/phy.c b/drivers/net/phy/phy.c
> index 45f75533c47c..fca8c3eebc5d 100644
> --- a/drivers/net/phy/phy.c
> +++ b/drivers/net/phy/phy.c
> @@ -1004,6 +1004,7 @@ EXPORT_SYMBOL(phy_free_interrupt);
>  void phy_stop(struct phy_device *phydev)
>  {
>  	struct net_device *dev = phydev->attached_dev;
> +	enum phy_state old_state;
>  
>  	if (!phy_is_started(phydev) && phydev->state != PHY_DOWN) {
>  		WARN(1, "called from state %s\n",
> @@ -1021,8 +1022,17 @@ void phy_stop(struct phy_device *phydev)
>  	if (phydev->sfp_bus)
>  		sfp_upstream_stop(phydev->sfp_bus);
>  
> +	old_state = phydev->state;
>  	phydev->state = PHY_HALTED;
>  
> +	if (old_state != phydev->state) {

This check shouldn't be needed because it shouldn't happen that
phy_stop() is called from status PHY_HALTED. In this case the
WARN() a few lines above would have fired already.

> +		phydev_err(phydev, "PHY state change %s -> %s\n",
> +			   phy_state_to_str(old_state),
> +			   phy_state_to_str(phydev->state));
> +		if (phydev->drv && phydev->drv->link_change_notify)
> +			phydev->drv->link_change_notify(phydev);

Instead of duplicating this code it could be factored out into
a small helper that is used by phy_stop() and phy_state_machine().

> +	}
> +
>  	mutex_unlock(&phydev->lock);
>  
>  	phy_state_machine(&phydev->state_queue.work);
>