linux-kernel - Re: [PATCH] net: phy: genphy_loopback: fix loopback failed when speed is unknown

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Date:   Thu, 31 Mar 2022 14:23:42 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Guangbin Huang <huangguangbin2@...wei.com>
Cc:     davem@...emloft.net, kuba@...nel.org, o.rempel@...gutronix.de,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        lipeng321@...wei.com, chenhao288@...ilicon.com
Subject: Re: [PATCH] net: phy: genphy_loopback: fix loopback failed when
 speed is unknown

On Thu, Mar 31, 2022 at 07:48:19PM +0800, Guangbin Huang wrote:
> If phy link status is down because link partner goes down, the phy speed
> will be updated to SPEED_UNKNOWN when autoneg on with general phy driver.
> If test loopback in this case, the phy speed will be set to 10M. However,
> the speed of mac may not be 10M, it causes loopback test failed.
> 
> To fix this problem, if speed is SPEED_UNKNOWN, don't configure link speed.

I don't think this explanation is correct.

If speed is UNKNOWN, ctl is just going to have BMCR_LOOPBACK set. That
is very similar to what you are doing. The code then waits for the
link to establish. This is where i guess your problem is. Are you
seeing ETIMEDOUT? Does the link not establish?

Thanks
	Andrew