Re: Regression: mv88e6xxx packet loss after 4.18's PHYLINK merge

[Andrew Lunn <andrew@lunn.ch>]

> Hi Andrew,
> 
> I tested the patch and it has an issue that prevents the carrier from turning
> on. I think it's caused by the change from using link_state to phy->phy_state,
> as later in the same function the link_state attributes are read when
> deciding if the carrier needs to be turned on.
 
Hi Samu

This version has had better testing. So i'm a bit more confident about
it.

	Andrew

From d093492f9aba75cb4844d15148e0efd014f193bb Mon Sep 17 00:00:00 2001
From: Andrew Lunn <andrew@lunn.ch>
Date: Wed, 16 Jan 2019 20:22:04 -0600
Subject: [PATCH] net: phy: phylink: Only change mac when fixed link changes
 state

phylink polls the fixed-link once per second to see if the GPIO has
changed state, or if the callback indicates if there has been a change
in state. It then calls the MAC to reconfigure itself to the current
state.

For some MACs, reconfiguration can result in packets being dropped.
Hence only reconfigure the MAC if the link state differs from the
netdev carrier state.

Reported-by: Samu Nuutamo <samu.nuutamo@vincit.fi>
Fixes: 9cd00a8aa42e ("net: phy: phylink: Poll link GPIOs")
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
---
 drivers/net/phy/phylink.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/phy/phylink.c b/drivers/net/phy/phylink.c
index e7becc7379d7..394b1eb5b55a 100644
--- a/drivers/net/phy/phylink.c
+++ b/drivers/net/phy/phylink.c
@@ -409,7 +409,8 @@ static void phylink_resolve(struct work_struct *w)
 
 		case MLO_AN_FIXED:
 			phylink_get_fixed_state(pl, &link_state);
-			phylink_mac_config(pl, &link_state);
+			if (link_state.link != netif_carrier_ok(ndev))
+				phylink_mac_config(pl, &link_state);
 			break;
 
 		case MLO_AN_INBAND:
-- 
2.20.1