net: dsa: sja1105: Really fix panic on unregistering PTP clock

The IS_ERR_OR_NULL(priv->clock) check inside
sja1105_ptp_clock_unregister() is preventing cancel_delayed_work_sync
from actually being run.

Additionally, sja1105_ptp_clock_unregister() does not actually get run,
when placed in sja1105_remove(). The DSA switch gets torn down, but the
sja1105 module does not get unregistered. So sja1105_ptp_clock_unregister
needs to be moved to sja1105_teardown, to be symmetrical with
sja1105_ptp_clock_register which is called from the DSA sja1105_setup.

It is strange to fix a "fixes" patch, but the probe failure can only be
seen when the attached PHY does not respond to MDIO (issue which I can't
pinpoint the reason to) and it goes away after I power-cycle the board.
This time the patch was validated on a failing board, and the kernel
panic from the fixed commit's message can no longer be seen.

Fixes: 29dd908d ("net: dsa: sja1105: Cancel PTP delayed work on unregister")
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/sja1105/sja1105_main.c

@@ -1728,6 +1728,8 @@ static void sja1105_teardown(struct dsa_switch *ds)
 
 	cancel_work_sync(&priv->tagger_data.rxtstamp_work);
 	skb_queue_purge(&priv->tagger_data.skb_rxtstamp_queue);
+	sja1105_ptp_clock_unregister(priv);
+	sja1105_static_config_free(&priv->static_config);
 }
 
 static int sja1105_mgmt_xmit(struct dsa_switch *ds, int port, int slot,
@@ -2185,9 +2187,7 @@ static int sja1105_remove(struct spi_device *spi)
 {
 	struct sja1105_private *priv = spi_get_drvdata(spi);
 
-	sja1105_ptp_clock_unregister(priv);
 	dsa_unregister_switch(priv->ds);
-	sja1105_static_config_free(&priv->static_config);
 	return 0;
 }
 

drivers/net/dsa/sja1105/sja1105_ptp.c

@@ -369,16 +369,15 @@ int sja1105_ptp_clock_register(struct sja1105_private *priv)
 		.mult = SJA1105_CC_MULT,
 	};
 	mutex_init(&priv->ptp_lock);
-	INIT_DELAYED_WORK(&priv->refresh_work, sja1105_ptp_overflow_check);
-
-	schedule_delayed_work(&priv->refresh_work, SJA1105_REFRESH_INTERVAL);
-
 	priv->ptp_caps = sja1105_ptp_caps;
 
 	priv->clock = ptp_clock_register(&priv->ptp_caps, ds->dev);
 	if (IS_ERR_OR_NULL(priv->clock))
 		return PTR_ERR(priv->clock);
 
+	INIT_DELAYED_WORK(&priv->refresh_work, sja1105_ptp_overflow_check);
+	schedule_delayed_work(&priv->refresh_work, SJA1105_REFRESH_INTERVAL);
+
 	return sja1105_ptp_reset(priv);
 }