Subject: [[PATCH,net]] net: dsa: mt7530: Change the LINK bit to reflect the link status

From: René van Dorst <[email-masked]>
Date: Thu, 19 Mar 2020 14:47:56 +0100

Andrew reported:

After a number of network port link up/down changes, sometimes the switch
port gets stuck in a state where it thinks it is still transmitting packets
but the cpu port is not actually transmitting anymore. In this state you
will see a message on the console
"mtk_soc_eth 1e100000.ethernet eth0: transmit timed out" and the Tx counter
in ifconfig will be incrementing on virtual port, but not incrementing on
cpu port.

The issue is that MAC TX/RX status has no impact on the link status or
queue manager of the switch. So the queue manager just queues up packets
of a disabled port and sends out pause frames when the queue is full.

Change the LINK bit to reflect the link status.

Fixes: b8f126a8d543 ("net-next: dsa: add dsa support for Mediatek MT7530 switch")
Reported-by: Andrew Smith <[email-masked]>
Signed-off-by: René van Dorst <[email-masked]>
---
 drivers/net/dsa/mt7530.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/dsa/mt7530.c b/drivers/net/dsa/mt7530.c
index 9ee3f263d529..d422d3d6a129 100644
--- a/drivers/net/dsa/mt7530.c
+++ b/drivers/net/dsa/mt7530.c
@@ -566,7 +566,7 @@ mt7530_mib_reset(struct dsa_switch *ds)
 static void
 mt7530_port_set_status(struct mt7530_priv *priv, int port, int enable)
 {
-	u32 mask = PMCR_TX_EN | PMCR_RX_EN;
+	u32 mask = PMCR_TX_EN | PMCR_RX_EN | PMCR_FORCE_LNK;
 
 	if (enable)
 		mt7530_set(priv, MT7530_PMCR_P(port), mask);
@@ -1512,7 +1512,7 @@ static void mt7530_phylink_mac_config(struct dsa_switch *ds, int port,
 	mcr_new &= ~(PMCR_FORCE_SPEED_1000 | PMCR_FORCE_SPEED_100 |
 		     PMCR_FORCE_FDX | PMCR_TX_FC_EN | PMCR_RX_FC_EN);
 	mcr_new |= PMCR_IFG_XMIT(1) | PMCR_MAC_MODE | PMCR_BACKOFF_EN |
-		   PMCR_BACKPR_EN | PMCR_FORCE_MODE | PMCR_FORCE_LNK;
+		   PMCR_BACKPR_EN | PMCR_FORCE_MODE;
 
 	/* Are we connected to external phy */
 	if (port == 5 && dsa_is_user_port(ds, 5))
-- 
2.25.1