Re: [PATCH net-next 3/6] net: stmmac: start phylink before setting up hardware

From: "Russell King (Oracle)" <linux@armlinux.org.uk>
To: "Clément Léger" <clement.leger@bootlin.com>
Cc: "Sergey Shtylyov" <s.shtylyov@omp.ru>,
	"David S. Miller" <davem@davemloft.net>,
	"Eric Dumazet" <edumazet@google.com>,
	"Jakub Kicinski" <kuba@kernel.org>,
	"Paolo Abeni" <pabeni@redhat.com>,
	"Rob Herring" <robh+dt@kernel.org>,
	"Krzysztof Kozlowski" <krzysztof.kozlowski+dt@linaro.org>,
	"Geert Uytterhoeven" <geert+renesas@glider.be>,
	"Magnus Damm" <magnus.damm@gmail.com>,
	"Giuseppe Cavallaro" <peppe.cavallaro@st.com>,
	"Alexandre Torgue" <alexandre.torgue@foss.st.com>,
	"Jose Abreu" <joabreu@synopsys.com>,
	"Maxime Coquelin" <mcoquelin.stm32@gmail.com>,
	"Wong Vee Khee" <veekhee@apple.com>,
	"Kurt Kanzenbach" <kurt@linutronix.de>,
	"Revanth Kumar Uppala" <ruppala@nvidia.com>,
	"Tan Tee Min" <tee.min.tan@linux.intel.com>,
	"Thomas Petazzoni" <thomas.petazzoni@bootlin.com>,
	"Herve Codina" <herve.codina@bootlin.com>,
	"Miquèl Raynal" <miquel.raynal@bootlin.com>,
	"Milan Stevanovic" <milan.stevanovic@se.com>,
	"Jimmy Lalande" <jimmy.lalande@se.com>,
	"Pascal Eberhard" <pascal.eberhard@se.com>,
	"Mohammad Athari Bin Ismail" <mohammad.athari.ismail@intel.com>,
	"Jon Hunter" <jonathanh@nvidia.com>,
	netdev@vger.kernel.org, linux-renesas-soc@vger.kernel.org,
	devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-stm32@st-md-mailman.stormreply.com,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH net-next 3/6] net: stmmac: start phylink before setting up hardware
Date: Mon, 16 Jan 2023 10:53:49 +0000	[thread overview]
Message-ID: <Y8UsvREsKOR2ejzT@shell.armlinux.org.uk> (raw)
In-Reply-To: <20230116103926.276869-4-clement.leger@bootlin.com>

On Mon, Jan 16, 2023 at 11:39:23AM +0100, Clément Léger wrote:
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> index f2247b8cf0a3..88c941003855 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> @@ -3818,6 +3818,12 @@ static int __stmmac_open(struct net_device *dev,
>  		}
>  	}
>  
> +	/* We need to setup the phy & PCS before accessing the stmmac registers
> +	 * because in some cases (RZ/N1), if the stmmac IP is not clocked by the
> +	 * PCS, hardware init will fail because it lacks a RGMII RX clock.
> +	 */
> +	phylink_start(priv->phylink);

So what happens if you end up with the mac_link_up method being called
at this point in the driver, before the hardware has been setup ?

If you use a fixed-link, that's a real possibility.

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