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

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Message-ID: <DB8PR04MB6795663DB5336C8BDB16A159E69F9@DB8PR04MB6795.eurprd04.prod.outlook.com>
Date:   Wed, 24 Feb 2021 02:13:05 +0000
From:   Joakim Zhang <qiangqing.zhang@....com>
To:     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: Jakub Kicinski <kuba@...nel.org>
> Sent: 2021年2月24日 9:55
> To: Joakim Zhang <qiangqing.zhang@....com>
> Cc: 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
> 
> On Wed, 24 Feb 2021 01:45:40 +0000 Joakim Zhang wrote:
> > > I'm not an expert on this stuff, but is there a reason you're not
> > > integrating this functionality with the power management subsystem?
> >
> > Do you mean that implement runtime power management for driver? If
> > yes, I think that is another feature, we can support later.
> 
> Runtime is a strong word, IIUC you can just implement the PM callbacks, and
> always resume in .open and always suspend in .close. Pretty much what you
> have already.
> 
> > > I don't think it'd change the functionality, but it'd feel more
> > > idiomatic to fit in the standard Linux framework.
> >
> > Yes, there is no functionality change, this patch set just adds clocks
> management.
> > In the driver now, we manage clocks at two point side:
> > 1. enable clocks when probe driver, disable clocks when remove driver.
> > 2. disable clocks when system suspend, enable clocks when system resume
> back.
> >
> > This should not be enough, such as, even we close the NIC, the clocks still
> enabled. So this patch improve below:
> > Keep clocks disabled after driver probe, enable clocks when NIC up, and then
> disable clocks when NIC down.
> > The aim is to enable clocks when it needs, others keep clocks disabled.
> 
> Understood. Please double check ethtool callbacks work fine. People often
> forget about those when disabling clocks in .close.

Hi Jakub,

If NIC is open then clocks are always enabled, so all ethtool callbacks should be okay.

Could you point me which ethtool callbacks could be invoked when NIC is closed? I'm not very familiar with ethtool use case. Thanks.

Best Regards,
Joakim Zhang