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

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Date:   Thu, 2 Feb 2023 21:24:38 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Clark Wang <xiaoning.wang@....com>
Cc:     peppe.cavallaro@...com, alexandre.torgue@...s.st.com,
        joabreu@...opsys.com, davem@...emloft.net, edumazet@...gle.com,
        pabeni@...hat.com, mcoquelin.stm32@...il.com,
        linux@...linux.org.uk, andrew@...n.ch, hkallweit1@...il.com,
        netdev@...r.kernel.org, linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-imx@....com
Subject: Re: [PATCH V3 1/2] net: phylink: add a function to resume phy alone
 to fix resume issue with WoL enabled

On Thu,  2 Feb 2023 16:15:59 +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@....com>

Patch 2/2 never made it to the list. You'll need to repost.
While I have you - some minor nit picks:

> +/**
> + * 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

You use MAC in capital letters buy phy in lower case, be consistent.

> + * when it resumes, can call this function to resume the phy separately.

missing "it" ? Otherwise the sentence is missing a subject.

> + * 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) {

&& goes at the end of the line, not start

> +		phy_start(pl->phydev);
> +		pl->mac_resume_phy_separately = true;
> +	}
> +
> +}
> +EXPORT_SYMBOL_GPL(phylink_phy_resume);