linux-kernel - Re: [PATCH net v3 2/3] net: stmmac: check if MAC needs to attach to a PHY

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Message-ID: <5bb39f85-7ef0-4cbb-a06b-0d6431ab09b7@roeck-us.net>
Date:   Wed, 5 Apr 2023 10:02:16 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Michael Sit Wei Hong <michael.wei.hong.sit@...el.com>
Cc:     Giuseppe Cavallaro <peppe.cavallaro@...com>,
        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>,
        Ong Boon Leong <boon.leong.ong@...el.com>,
        netdev@...r.kernel.org, linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux@...linux.org.uk, Looi Hong Aun <hong.aun.looi@...el.com>,
        Voon Weifeng <weifeng.voon@...el.com>,
        Lai Peter Jun Ann <peter.jun.ann.lai@...el.com>
Subject: Re: [PATCH net v3 2/3] net: stmmac: check if MAC needs to attach to
 a PHY

Hi,

On Fri, Mar 24, 2023 at 04:16:55PM +0800, Michael Sit Wei Hong wrote:
> After the introduction of the fixed-link support, the MAC driver
> no longer attempt to scan for a PHY to attach to. This causes the
> non fixed-link setups to stop working.
> 
> Using the phylink_expects_phy() to check and determine if the MAC
> should expect and attach a PHY.
> 
> Fixes: ab21cf920928 ("net: stmmac: make mdio register skips PHY scanning for fixed-link")
> Signed-off-by: Michael Sit Wei Hong <michael.wei.hong.sit@...el.com>
> Signed-off-by: Lai Peter Jun Ann <peter.jun.ann.lai@...el.com>

With this patch in linux-next, the orangepi-pc qemu emulation fails to
bring up the Ethernet interface. The following error is seen.

[   12.482401] dwmac-sun8i 1c30000.ethernet eth0: Register MEM_TYPE_PAGE_POOL RxQ-0
[   12.487789] dwmac-sun8i 1c30000.ethernet eth0: PHY [mdio_mux-0.1:01] driver [Generic PHY] (irq=POLL)
[   12.488177] dwmac-sun8i 1c30000.ethernet eth0: no phy found
[   12.488295] dwmac-sun8i 1c30000.ethernet eth0: __stmmac_open: Cannot attach to PHY (error: -19)

Reverting this patch fixes the problem.

> ---
>  drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> index 8f543c3ab5c5..41f0f3b74933 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> @@ -1135,6 +1135,7 @@ static int stmmac_init_phy(struct net_device *dev)
>  {
>  	struct stmmac_priv *priv = netdev_priv(dev);
>  	struct fwnode_handle *fwnode;
> +	bool phy_needed;
>  	int ret;
>  
>  	fwnode = of_fwnode_handle(priv->plat->phylink_node);
> @@ -1144,10 +1145,11 @@ static int stmmac_init_phy(struct net_device *dev)
>  	if (fwnode)
>  		ret = phylink_fwnode_phy_connect(priv->phylink, fwnode, 0);
>  
> +	phy_needed = phylink_expects_phy(priv->phylink);
>  	/* Some DT bindings do not set-up the PHY handle. Let's try to
>  	 * manually parse it
>  	 */
> -	if (!fwnode || ret) {
> +	if (!fwnode || phy_needed || ret) {

I don't really understand this condition. It starts taking this path even if ret == 0
and fwnode != NULL if phy_needed is set. That means this path is now taken even if
phylink_fwnode_phy_connect() returned no error. That seems odd.

Guenter

>  		int addr = priv->plat->phy_addr;
>  		struct phy_device *phydev;
>  
> -- 
> 2.34.1
>