can: mcp251x: Fix resume from sleep before interface was brought up

Since 8ce8c0a the driver queues work via priv->restart_work when
resuming after suspend, even when the interface was not previously
enabled. This causes a null dereference error as the workqueue is
only allocated and initialized in mcp251x_open().

To fix this we move the workqueue init to mcp251x_can_probe() as
there is no reason to do it later and repeat it whenever
mcp251x_open() is called.

Fixes: 8ce8c0a ("can: mcp251x: only reset hardware as required")
Cc: stable@vger.kernel.org
Signed-off-by: Frieder Schrempf <frieder.schrempf@kontron.de>

drivers/net/can/spi/mcp251x.c

@@ -956,8 +956,6 @@ static int mcp251x_stop(struct net_device *net)
 
 	priv->force_quit = 1;
 	free_irq(spi->irq, priv);
-	destroy_workqueue(priv->wq);
-	priv->wq = NULL;
 
 	mutex_lock(&priv->mcp_lock);
 
@@ -1224,15 +1222,6 @@ static int mcp251x_open(struct net_device *net)
 		goto out_close;
 	}
 
-	priv->wq = alloc_workqueue("mcp251x_wq", WQ_FREEZABLE | WQ_MEM_RECLAIM,
-				   0);
-	if (!priv->wq) {
-		ret = -ENOMEM;
-		goto out_clean;
-	}
-	INIT_WORK(&priv->tx_work, mcp251x_tx_work_handler);
-	INIT_WORK(&priv->restart_work, mcp251x_restart_work_handler);
-
 	ret = mcp251x_hw_wake(spi);
 	if (ret)
 		goto out_free_wq;
@@ -1373,6 +1362,15 @@ static int mcp251x_can_probe(struct spi_device *spi)
 	if (ret)
 		goto out_clk;
 
+	priv->wq = alloc_workqueue("mcp251x_wq", WQ_FREEZABLE | WQ_MEM_RECLAIM,
+				   0);
+	if (!priv->wq) {
+		ret = -ENOMEM;
+		goto out_clk;
+	}
+	INIT_WORK(&priv->tx_work, mcp251x_tx_work_handler);
+	INIT_WORK(&priv->restart_work, mcp251x_restart_work_handler);
+
 	priv->spi = spi;
 	mutex_init(&priv->mcp_lock);
 
@@ -1417,6 +1415,8 @@ static int mcp251x_can_probe(struct spi_device *spi)
 	return 0;
 
 error_probe:
+	destroy_workqueue(priv->wq);
+	priv->wq = NULL;
 	mcp251x_power_enable(priv->power, 0);
 
 out_clk:
@@ -1438,6 +1438,9 @@ static int mcp251x_can_remove(struct spi_device *spi)
 
 	mcp251x_power_enable(priv->power, 0);
 
+	destroy_workqueue(priv->wq);
+	priv->wq = NULL;
+
 	clk_disable_unprepare(priv->clk);
 
 	free_candev(net);