linux-kernel - Re: [PATCH net 1/1] net: stmmac: fix MAC and phylink mismatch issue after resume with STMMAC_FLAG_USE_PHY

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Message-ID: <ZUyjOEQHHnnbzwrV@shell.armlinux.org.uk>
Date:   Thu, 9 Nov 2023 09:15:36 +0000
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Gan Yi Fang <yi.fang.gan@...el.com>
Cc:     Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Jose Abreu <joabreu@...opsys.com>,
        "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Joakim Zhang <qiangqing.zhang@....com>, netdev@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Looi Hong Aun <hong.aun.looi@...el.com>,
        Voon Weifeng <weifeng.voon@...el.com>,
        Song Yoong Siang <yoong.siang.song@...el.com>
Subject: Re: [PATCH net 1/1] net: stmmac: fix MAC and phylink mismatch issue
 after resume with STMMAC_FLAG_USE_PHY_WOL enabled

On Thu, Nov 09, 2023 at 01:00:27PM +0800, Gan Yi Fang wrote:
> From: "Gan, Yi Fang" <yi.fang.gan@...el.com>
> 
> The issue happened when flag STMMAC_FLAG_USE_PHY_WOL is enabled.
> It can be reproduced with steps below:
> 1. Advertise only one speed on the host
> 2. Enable the WoL on the host
> 3. Suspend the host
> 4. Wake up the host
> 
> When the WoL is disabled, both the PHY and MAC will suspend and wake up
> with everything configured well. When WoL is enabled, the PHY needs to be
> stay awake to receive the signal from remote client but MAC will enter
> suspend mode.
> 
> When the MAC resumes from suspend, phylink_resume() will call
> phylink_start() to start the phylink instance which will trigger the
> phylink machine to invoke the mac_link_up callback function. The
> stmmac_mac_link_up() will configure the MAC_CTRL_REG based on the current
> link state. Then the stmmac_hw_setup() will be called to configure the MAC.
> 
> This sequence might cause mismatch of the link state between MAC and
> phylink. This patch moves the phylink_resume() after stmamc_hw_setup() to
> ensure the MAC is initialized before phylink is being configured.

Isn't this going to cause problems?

stmamc_hw_setup() calls stmmac_init_dma_engine(), which then calls
stmmac_reset() - and stmmac_reset() can fail if the PHY clock isn't
running, which is why phylink_resume() gets called before this.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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