netdev - RE: [PATCH V1 net-next 0/3] net: stmmac: implement clocks

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Message-ID: <DB8PR04MB67954D68397236C56A0DB2DBE69E9@DB8PR04MB6795.eurprd04.prod.outlook.com>
Date:   Thu, 25 Feb 2021 02:15:24 +0000
From:   Joakim Zhang <qiangqing.zhang@....com>
To:     Andrew Lunn <andrew@...n.ch>, Jakub Kicinski <kuba@...nel.org>
CC:     "peppe.cavallaro@...com" <peppe.cavallaro@...com>,
        "alexandre.torgue@...com" <alexandre.torgue@...com>,
        "joabreu@...opsys.com" <joabreu@...opsys.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>
Subject: RE: [PATCH V1 net-next 0/3] net: stmmac: implement clocks


> -----Original Message-----
> From: Andrew Lunn <andrew@...n.ch>
> Sent: 2021年2月24日 21:02
> To: Jakub Kicinski <kuba@...nel.org>
> Cc: Joakim Zhang <qiangqing.zhang@....com>; peppe.cavallaro@...com;
> alexandre.torgue@...com; joabreu@...opsys.com; davem@...emloft.net;
> netdev@...r.kernel.org; dl-linux-imx <linux-imx@....com>
> Subject: Re: [PATCH V1 net-next 0/3] net: stmmac: implement clocks
> 
> > Understood. Please double check ethtool callbacks work fine. People
> > often forget about those when disabling clocks in .close.
> 
> The MDIO bus can also be used at any time, not just when the interface is open.
> For example the MAC could be connected to an Ethernet switch, which is
> managed by the MDIO bus. Or some PHYs have a temperature sensor which is
> registered with HWMON when the PHY is probed.

Hi Andrew,

I don't have experience with Ethernet switch, according to your points, you mean we can connect STMMAC to an Ethernet switch, and then Ethernet switch managed STMMAC by the MDIO bus but without checking whether STMMAC interface is opened or not, so STMMAC needs clocks for MDIO even interface is closed, right?

> You said you copied the FEC driver. Take a look at that, it was initially broken in
> this way, and i needed to extend it when i got a board with an Ethernet switch
> attached to the FEC.

Could you point me how to implement clocks management to cover above Ethernet switch case? Or can we upstream this first and then fix it later for such case?

Best Regards,
Joakim Zhang
> 
>       Andrew