[PATCH AUTOSEL 5.4 270/350] net: dsa: sja1105: Disallow management xmit during switch reset

[Sasha Levin]

From: Vladimir Oltean <olteanv@xxxxxxxxx>

[ Upstream commit af580ae2dcb250719857b4b7024bd4bb0c2e05fb ]

The purpose here is to avoid ptp4l fail due to this condition:

  timed out while polling for tx timestamp
  increasing tx_timestamp_timeout may correct this issue, but it is likely caused by a driver bug
  port 1: send peer delay request failed

So either reset the switch before the management frame was sent, or
after it was timestamped as well, but not in the middle.

The condition may arise either due to a true timeout (i.e. because
re-uploading the static config takes time), or due to the TX timestamp
actually getting lost due to reset. For the former we can increase
tx_timestamp_timeout in userspace, for the latter we need this patch.

Locking all traffic during switch reset does not make sense at all,
though. Forcing all CPU-originated traffic to potentially block waiting
for a sleepable context to send > 800 bytes over SPI is not a good idea.
Flows that are autonomously forwarded by the switch will get dropped
anyway during switch reset no matter what. So just let all other
CPU-originated traffic be dropped as well.

Signed-off-by: Vladimir Oltean <olteanv@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/net/dsa/sja1105/sja1105_main.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/net/dsa/sja1105/sja1105_main.c b/drivers/net/dsa/sja1105/sja1105_main.c
index aa140662c7c20..4e5a428ab1a4c 100644
--- a/drivers/net/dsa/sja1105/sja1105_main.c
+++ b/drivers/net/dsa/sja1105/sja1105_main.c
@@ -1389,6 +1389,8 @@ int sja1105_static_config_reload(struct sja1105_private *priv)
 	int speed_mbps[SJA1105_NUM_PORTS];
 	int rc, i;
 
+	mutex_lock(&priv->mgmt_lock);
+
 	mac = priv->static_config.tables[BLK_IDX_MAC_CONFIG].entries;
 
 	/* Back up the dynamic link speed changed by sja1105_adjust_port_config
@@ -1420,6 +1422,8 @@ int sja1105_static_config_reload(struct sja1105_private *priv)
 			goto out;
 	}
 out:
+	mutex_unlock(&priv->mgmt_lock);
+
 	return rc;
 }
 
-- 
2.20.1