linux-kernel - Re: [PATCH] net: stmmac: linkup phy after enabled mac when system resume

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Message-ID: <Y0/yWHvHs6NHdB8W@shell.armlinux.org.uk>
Date:   Wed, 19 Oct 2022 13:49:28 +0100
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Clark Wang <xiaoning.wang@....com>
Cc:     peppe.cavallaro@...com, alexandre.torgue@...s.st.com,
        joabreu@...opsys.com, davem@...emloft.net, edumazet@...gle.com,
        kuba@...nel.org, pabeni@...hat.com, mcoquelin.stm32@...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] net: stmmac: linkup phy after enabled mac when system
 resume

On Wed, Oct 19, 2022 at 08:36:43PM +0800, Clark Wang wrote:
> +	mutex_unlock(&priv->lock);
> +	if (device_may_wakeup(priv->device) && priv->plat->pmt) {
> +		phylink_resume(priv->phylink);
> +	} else {
> +		phylink_resume(priv->phylink);
> +		if (device_may_wakeup(priv->device))
> +			phylink_speed_up(priv->phylink);
> +	}
> +	mutex_lock(&priv->lock);

First, is there a reason this isn't coded as:

	mutex_unlock(&priv->lock);
	phylink_resume(priv->phylink);

	if (!priv->plat->pmt && device_may_wakeup(priv->device))
		phylink_speed_up(priv->phylink);

	mutex_lock(&priv->lock);

And secondly, is it really safe to drop this lock? What specifically
is the lock protecting? I see this isn't documented in the driver...

-- 
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