Subject: Re: [PATCH net-next 3/4] net: ethernet: introduce phy_set_pause

From: Russell King - ARM Linux admin <[email-masked]>
Date: Wed, 13 May 2020 10:42:39 +0100

On Mon, May 11, 2020 at 05:24:09PM -0700, Doug Berger wrote:
> This commit introduces the phy_set_pause function to the phylib as
> a helper to support the set_pauseparam ethtool method.
> 
> It is hoped that the new behavior introduced by this function will
> be widely embraced and the phy_set_sym_pause and phy_set_asym_pause
> functions can be deprecated. Those functions are retained for all
> existing users and for any desenting opinions on my interpretation
> of the functionality.
> 
> Signed-off-by: Doug Berger <[email-masked]>
> ---
>  drivers/net/phy/phy_device.c | 31 +++++++++++++++++++++++++++++++
>  include/linux/phy.h          |  1 +
>  2 files changed, 32 insertions(+)
> 
> diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
> index 48ab9efa0166..e6dafb3c3e5f 100644
> --- a/drivers/net/phy/phy_device.c
> +++ b/drivers/net/phy/phy_device.c
> @@ -2614,6 +2614,37 @@ void phy_set_asym_pause(struct phy_device *phydev, bool rx, bool tx)
>  EXPORT_SYMBOL(phy_set_asym_pause);
>  
>  /**
> + * phy_set_pause - Configure Pause and Asym Pause with autoneg
> + * @phydev: target phy_device struct
> + * @rx: Receiver Pause is supported
> + * @tx: Transmit Pause is supported
> + * @autoneg: Auto neg should be used
> + *
> + * Description: Configure advertised Pause support depending on if
> + * receiver pause and pause auto neg is supported. Generally called
> + * from the set_pauseparam ethtool_ops.
> + *
> + * Note: Since pause is really a MAC level function it should be
> + * notified via adjust_link to update its pause functions.
> + */
> +void phy_set_pause(struct phy_device *phydev, bool rx, bool tx, bool autoneg)
> +{
> +	linkmode_set_pause(phydev->advertising, tx, rx, autoneg);
> +
> +	/* Reset the state of an already running link to force a new
> +	 * link up event when advertising doesn't change or when PHY
> +	 * autoneg is disabled.
> +	 */
> +	mutex_lock(&phydev->lock);
> +	if (phydev->state == PHY_RUNNING)
> +		phydev->state = PHY_UP;
> +	mutex_unlock(&phydev->lock);

I wonder about this - will drivers cope with having two link-up events
via adjust_link without a corresponding link-down event?  What if they
touch registers that are only supposed to be touched while the link is
down?  Obviously, drivers have to opt-in to this interface, so it may
be okay provided we don't get wholesale changes.

> +
> +	phy_start_aneg(phydev);

Should we be making that conditional on something changing and autoneg
being enabled, like phy_set_asym_pause() does?  There is no point
interrupting an established link if the advertisement didn't change.

> +}
> +EXPORT_SYMBOL(phy_set_pause);
> +
> +/**
>   * phy_validate_pause - Test if the PHY/MAC support the pause configuration
>   * @phydev: phy_device struct
>   * @pp: requested pause configuration
> diff --git a/include/linux/phy.h b/include/linux/phy.h
> index 5d8ff5428010..71e484424e68 100644
> --- a/include/linux/phy.h
> +++ b/include/linux/phy.h
> @@ -1403,6 +1403,7 @@ void phy_support_asym_pause(struct phy_device *phydev);
>  void phy_set_sym_pause(struct phy_device *phydev, bool rx, bool tx,
>  		       bool autoneg);
>  void phy_set_asym_pause(struct phy_device *phydev, bool rx, bool tx);
> +void phy_set_pause(struct phy_device *phydev, bool rx, bool tx, bool autoneg);
>  bool phy_validate_pause(struct phy_device *phydev,
>  			struct ethtool_pauseparam *pp);
>  void phy_get_pause(struct phy_device *phydev, bool *tx_pause, bool *rx_pause);
> -- 
> 2.7.4
> 
> 

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