Re: [PATCH V3 1/2] net: phylink: add a function to resume phy alone to fix resume issue with WoL enabled

[Paolo Abeni]

On Thu, 2023-02-02 at 16:15 +0800, Clark Wang wrote:
> Issue we met:
> On some platforms, mac cannot work after resumed from the suspend with WoL
> enabled.
> 
> The cause of the issue:
> 1. phylink_resolve() is in a workqueue which will not be executed immediately.
>    This is the call sequence:
>        phylink_resolve()->phylink_link_up()->pl->mac_ops->mac_link_up()
>    For stmmac driver, mac_link_up() will set the correct speed/duplex...
>    values which are from link_state.
> 2. In stmmac_resume(), it will call stmmac_hw_setup() after called the
>    phylink_resume(), because mac need phy rx_clk to do the reset.
>    stmmac_core_init() is called in function stmmac_hw_setup(), which will
>    reset the mac and set the speed/duplex... to default value.
> Conclusion: Because phylink_resolve() cannot determine when it is called, it
>             cannot be guaranteed to be called after stmmac_core_init().
> 	    Once stmmac_core_init() is called after phylink_resolve(),
> 	    the mac will be misconfigured and cannot be used.
> 
> In order to avoid this problem, add a function called phylink_phy_resume()
> to resume phy separately. This eliminates the need to call phylink_resume()
> before stmmac_hw_setup().
> 
> Add another judgement before called phy_start() in phylink_start(). This way
> phy_start() will not be called multiple times when resumes. At the same time,
> it may not affect other drivers that do not use phylink_phy_resume().
> 
> Signed-off-by: Clark Wang <xiaoning.wang@xxxxxxx>
> ---
> V2 change:
>  - add mac_resume_phy_separately flag to struct phylink to mark if the mac
>    driver uses the phylink_phy_resume() first.
> V3 change:
>  - add brace to avoid ambiguous 'else'
>    Reported-by: kernel test robot <lkp@xxxxxxxxx>
> ---
>  drivers/net/phy/phylink.c | 32 ++++++++++++++++++++++++++++++--
>  include/linux/phylink.h   |  1 +
>  2 files changed, 31 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/phy/phylink.c b/drivers/net/phy/phylink.c
> index 319790221d7f..c2fe66f0b78f 100644
> --- a/drivers/net/phy/phylink.c
> +++ b/drivers/net/phy/phylink.c
> @@ -80,6 +80,8 @@ struct phylink {
>  	DECLARE_PHY_INTERFACE_MASK(sfp_interfaces);
>  	__ETHTOOL_DECLARE_LINK_MODE_MASK(sfp_support);
>  	u8 sfp_port;
> +
> +	bool mac_resume_phy_separately;
>  };
>  
>  #define phylink_printk(level, pl, fmt, ...) \
> @@ -1509,6 +1511,7 @@ struct phylink *phylink_create(struct phylink_config *config,
>  		return ERR_PTR(-EINVAL);
>  	}
>  
> +	pl->mac_resume_phy_separately = false;
>  	pl->using_mac_select_pcs = using_mac_select_pcs;
>  	pl->phy_state.interface = iface;
>  	pl->link_interface = iface;
> @@ -1943,8 +1946,12 @@ void phylink_start(struct phylink *pl)
>  	}
>  	if (poll)
>  		mod_timer(&pl->link_poll, jiffies + HZ);
> -	if (pl->phydev)
> -		phy_start(pl->phydev);
> +	if (pl->phydev) {
> +		if (!pl->mac_resume_phy_separately)
> +			phy_start(pl->phydev);
> +		else
> +			pl->mac_resume_phy_separately = false;
> +	}
>  	if (pl->sfp_bus)
>  		sfp_upstream_start(pl->sfp_bus);
>  }
> @@ -2024,6 +2031,27 @@ void phylink_suspend(struct phylink *pl, bool mac_wol)
>  }
>  EXPORT_SYMBOL_GPL(phylink_suspend);
>  
> +/**
> + * phylink_phy_resume() - resume phy alone
> + * @pl: a pointer to a &struct phylink returned from phylink_create()
> + *
> + * In the MAC driver using phylink, if the MAC needs the clock of the phy
> + * when it resumes, can call this function to resume the phy separately.
> + * Then proceed to MAC resume operations.
> + */
> +void phylink_phy_resume(struct phylink *pl)
> +{
> +	ASSERT_RTNL();
> +
> +	if (!test_bit(PHYLINK_DISABLE_MAC_WOL, &pl->phylink_disable_state)
> +	    && pl->phydev) {
> +		phy_start(pl->phydev);
> +		pl->mac_resume_phy_separately = true;
> +	}
> +

Minor nit: the empty line here is not needed.

Cheers,

Paolo