linux-kernel - Re: [PATCH 1/1] Revert "drivers/net/ftgmac100: fix DHCP potential failure with systemd"

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Message-ID: <4a639a86-37e2-4b3d-b870-f85f2c86cb81@lunn.ch>
Date: Fri, 12 Sep 2025 22:24:58 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Jian Zhang <zhangjian.3032@...edance.com>
Cc: netdev@...r.kernel.org, davem@...emloft.net, andrew+netdev@...n.ch,
	guoheyi@...ux.alibaba.com, Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Jacky Chou <jacky_chou@...eedtech.com>,
	Simon Horman <horms@...nel.org>,
	Heiner Kallweit <hkallweit1@...il.com>,
	Uwe Kleine-König <u.kleine-koenig@...libre.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] Revert "drivers/net/ftgmac100: fix DHCP potential
 failure with systemd"

On Fri, Sep 12, 2025 at 11:45:38AM +0800, Jian Zhang wrote:
> This reverts commit 1baf2e50e48f10f0ea07d53e13381fd0da1546d2.

> * rtnetlink is setting the link down
> * the PHY state_queue is triggered and calls ftgmac100_adjust_link
> -	/* Release phy lock to allow ftgmac100_reset to acquire it, keeping lock
> -	 * order consistent to prevent dead lock.
> -	 */
> -	if (netdev->phydev)
> -		mutex_unlock(&netdev->phydev->lock);
> -
> -	ftgmac100_reset(priv);
> -
> -	if (netdev->phydev)
> -		mutex_lock(&netdev->phydev->lock);
> -
> +	/* Reset the adapter asynchronously */
> +	schedule_work(&priv->reset_task);
>  }

So we are swapping one set of bugs for another set of bugs.

No other adjust_link callback messes with locks like this.  Have you
investigated what actually needs to be done by adjust_link?

Determining maccr in ftgmac100_reset_and_config_mac() look relevant.
Does it actually need a reset, or is it sufficient to just set the
bits in FTGMAC100_OFFSET_MACCR?

ftgmac100_config_pause() is called from ftgmac100_set_pauseparam()
suggesting it can be called at any time.

So i think the crux of the problem is what needs to happen to set bits
in MACCR.

	Andrew