netdev - Re: [PATCH net v3] net: phy: smsc: fix printing too many logs

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Date:   Sat, 20 Jun 2020 17:41:16 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Dejin Zheng <zhengdejin5@...il.com>
Cc:     f.fainelli@...il.com, hkallweit1@...il.com, linux@...linux.org.uk,
        davem@...emloft.net, kuba@...nel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Kevin Groeneveld <kgroeneveld@...il.com>
Subject: Re: [PATCH net v3] net: phy: smsc: fix printing too many logs

On Sat, Jun 20, 2020 at 10:55:34PM +0800, Dejin Zheng wrote:
> Commit 7ae7ad2f11ef47 ("net: phy: smsc: use phy_read_poll_timeout()
> to simplify the code") will print a lot of logs as follows when Ethernet
> cable is not connected:
> 
> [    4.473105] SMSC LAN8710/LAN8720 2188000.ethernet-1:00: lan87xx_read_status failed: -110
> 
> When wait 640 ms for check ENERGYON bit, the timeout should not be
> regarded as an actual error and an error message also should not be
> printed. due to a hardware bug in LAN87XX device, it leads to unstable
> detection of plugging in Ethernet cable when LAN87xx is in Energy Detect
> Power-Down mode. 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 and this commit was modified to prints an error message. it is an
> inappropriate conversion by used phy_read_poll_timeout() to introduce
> this bug. so fix this issue by use read_poll_timeout() to replace
> phy_read_poll_timeout().
> 
> Fixes: 7ae7ad2f11ef47 ("net: phy: smsc: use phy_read_poll_timeout() to simplify the code")
> Reported-by: Kevin Groeneveld <kgroeneveld@...il.com>
> Signed-off-by: Dejin Zheng <zhengdejin5@...il.com>

Reviewed-by: Andrew Lunn <andrew@...n.ch>

    Andrew