linux-kernel - Re: [PATCH net v1] net: phy: smsc: fix printing too many logs

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Date:   Wed, 17 Jun 2020 23:36:42 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Russell King - ARM Linux admin <linux@...linux.org.uk>
Cc:     Dejin Zheng <zhengdejin5@...il.com>, f.fainelli@...il.com,
        hkallweit1@...il.com, davem@...emloft.net, kuba@...nel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Kevin Groeneveld <kgroeneveld@...il.com>
Subject: Re: [PATCH net v1] net: phy: smsc: fix printing too many logs

On Wed, Jun 17, 2020 at 09:24:50PM +0100, Russell King - ARM Linux admin wrote:
> On Wed, Jun 17, 2020 at 08:43:34PM +0200, Andrew Lunn wrote:
> > You have explained what the change does. But not why it is
> > needed. What exactly is happening. To me, the key thing is
> > understanding why we get -110, and why it is not an actual error we
> > should be reporting as an error. That is what needs explaining.
> 
> The patch author really ought to be explaining this... but let me
> have a go.  It's worth pointing out that the comments in the file
> aren't good English either, so don't really describe what is going
> on.
> 
> When this PHY is in EDPD mode, it doesn't always detect a connected
> cable.  The workaround for it involves, when the link is down, and
> at each read_status() call:
> 
> - disable EDPD mode, forcing the PHY out of low-power mode
> - waiting 640ms to see if we have any energy detected from the media
> - re-enable entry to EDPD mode
> 
> This is presumably enough to allow the PHY to notice that a cable is
> connected, and resume normal operations to negotiate with the partner.
> 
> The problem is that when no media is detected, the 640ms wait times
> out (as it should, we don't want to wait forever) and the kernel
> prints a warning.

Hi Russell

Yes, that is what i was thinking. 

There probably should be a comment added just to prevent somebody
swapping it back to phy_read_poll_timeout(). It is not clear that
-ETIMEOUT is expected under some conditions.

	  Andrew