linux-kernel - Re: [PATCH net-next] net: stmmac: Fix the case when PHY handle is not present

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Date:   Wed, 26 Jun 2019 00:26:58 +0900
From:   Katsuhiro Suzuki <katsuhiro@...suster.net>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Jose Abreu <Jose.Abreu@...opsys.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Joao Pinto <Joao.Pinto@...opsys.com>,
        "David S . Miller" <davem@...emloft.net>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...com>
Subject: Re: [PATCH net-next] net: stmmac: Fix the case when PHY handle is not
 present

Hello Andrew,

On 2019/06/25 23:51, Andrew Lunn wrote:
> On Tue, Jun 25, 2019 at 11:40:00PM +0900, Katsuhiro Suzuki wrote:
>> Hello Jose,
>>
>> This patch works fine with my Tinker Board. Thanks a lot!
>>
>> Tested-by: Katsuhiro Suzuki <katsuhiro@...suster.net>
>>
>>
>> BTW, from network guys point of view, is it better to add a phy node
>> into device trees that have no phy node such as the Tinker Board?
> 
> Hi Katsuhiro
> 
> It makes it less ambiguous if there is a phy-handle. It is then very
> clear which PHY should be used. For a development board, which people
> can be tinkering around with, there is a chance they add a second PHY
> to the MDIO bus, or an Ethernet switch, etc. Without explicitly
> listing the PHY, it might get the wrong one. However this is generally
> a problem if phy_find_first() is used. I think in this case, something
> is setting priv->plat->phy_addr, so it is also clearly defined which
> PHY to use.
> 
> 	  Andrew
> 

Hmm, I see. This stmmac driver can choose PHY by the kernel module
parameter 'phyaddr' (if no one set this parameter, priv->plat->phy_addr
goes to 0). So there is no ambiguous in this case and need no changes
for device tree.

Thank you for your comment.

Best Regards,
Katsuhiro Suzuki