net: dsa: qca: ar9331: fix sleeping function called from invalid context bug

With lockdep enabled, we will get following warning:

 ar9331_switch ethernet.1:10 lan0 (uninitialized): PHY [!ahb!ethernet@1a000000!mdio!switch@10:00] driver [Qualcomm Atheros AR9331 built-in PHY] (irq=13)
 BUG: sleeping function called from invalid context at kernel/locking/mutex.c:935
 in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 18, name: kworker/0:1
 INFO: lockdep is turned off.
 irq event stamp: 602
 hardirqs last  enabled at (601): [<8073fde0>] _raw_spin_unlock_irq+0x3c/0x80
 hardirqs last disabled at (602): [<8073a4f4>] __schedule+0x184/0x800
 softirqs last  enabled at (0): [<80080f60>] copy_process+0x578/0x14c8
 softirqs last disabled at (0): [<00000000>] 0x0
 CPU: 0 PID: 18 Comm: kworker/0:1 Not tainted 5.10.0-rc3-ar9331-00734-g7d644991df0c #31
 Workqueue: events deferred_probe_work_func
 Stack : 80980000 80980000 8089ef70 80890000 804b5414 80980000 00000002 80b53728
         00000000 800d1268 804b5414 ffffffde 00000017 800afe08 81943860 0f5bfc32
         00000000 00000000 8089ef70 819436c0 ffffffea 00000000 00000000 00000000
         8194390c 808e353c 0000000f 66657272 80980000 00000000 00000000 80890000
         804b5414 80980000 00000002 80b53728 00000000 00000000 00000000 80d40000
         ...
 Call Trace:
 [<80069ce0>] show_stack+0x9c/0x140
 [<800afe08>] ___might_sleep+0x220/0x244
 [<8073bfb0>] __mutex_lock+0x70/0x374
 [<8073c2e0>] mutex_lock_nested+0x2c/0x38
 [<804b5414>] regmap_update_bits_base+0x38/0x8c
 [<804ee584>] regmap_update_bits+0x1c/0x28
 [<804ee714>] ar9331_sw_unmask_irq+0x34/0x60
 [<800d91f0>] unmask_irq+0x48/0x70
 [<800d93d4>] irq_startup+0x114/0x11c
 [<800d65b4>] __setup_irq+0x4f4/0x6d0
 [<800d68a0>] request_threaded_irq+0x110/0x190
 [<804e3ef0>] phy_request_interrupt+0x4c/0xe4
 [<804df508>] phylink_bringup_phy+0x2c0/0x37c
 [<804df7bc>] phylink_of_phy_connect+0x118/0x130
 [<806c1a64>] dsa_slave_create+0x3d0/0x578
 [<806bc4ec>] dsa_register_switch+0x934/0xa20
 [<804eef98>] ar9331_sw_probe+0x34c/0x364
 [<804eb48c>] mdio_probe+0x44/0x70
 [<8049e3b4>] really_probe+0x30c/0x4f4
 [<8049ea10>] driver_probe_device+0x264/0x26c
 [<8049bc10>] bus_for_each_drv+0xb4/0xd8
 [<8049e684>] __device_attach+0xe8/0x18c
 [<8049ce58>] bus_probe_device+0x48/0xc4
 [<8049db70>] deferred_probe_work_func+0xdc/0xf8
 [<8009ff64>] process_one_work+0x2e4/0x4a0
 [<800a0770>] worker_thread+0x2a8/0x354
 [<800a774c>] kthread+0x16c/0x174
 [<8006306c>] ret_from_kernel_thread+0x14/0x1c

 ar9331_switch ethernet.1:10 lan1 (uninitialized): PHY [!ahb!ethernet@1a000000!mdio!switch@10:02] driver [Qualcomm Atheros AR9331 built-in PHY] (irq=13)
 DSA: tree 0 setup

To fix it, it is better to move access to MDIO register to the .irq_bus_sync_unlock
call back.

Fixes: ec6698c2 ("net: dsa: add support for Atheros AR9331 built-in switch")
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Link: https://lore.kernel.org/r/20201211110317.17061-1-o.rempel@pengutronix.deSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/dsa/qca/ar9331.c

@@ -159,6 +159,8 @@ struct ar9331_sw_priv {
 	struct dsa_switch ds;
 	struct dsa_switch_ops ops;
 	struct irq_domain *irqdomain;
+	u32 irq_mask;
+	struct mutex lock_irq;
 	struct mii_bus *mbus; /* mdio master */
 	struct mii_bus *sbus; /* mdio slave */
 	struct regmap *regmap;
@@ -520,32 +522,44 @@ static irqreturn_t ar9331_sw_irq(int irq, void *data)
 static void ar9331_sw_mask_irq(struct irq_data *d)
 {
 	struct ar9331_sw_priv *priv = irq_data_get_irq_chip_data(d);
-	struct regmap *regmap = priv->regmap;
-	int ret;
 
-	ret = regmap_update_bits(regmap, AR9331_SW_REG_GINT_MASK,
-				 AR9331_SW_GINT_PHY_INT, 0);
-	if (ret)
-		dev_err(priv->dev, "could not mask IRQ\n");
+	priv->irq_mask = 0;
 }
 
 static void ar9331_sw_unmask_irq(struct irq_data *d)
+{
+	struct ar9331_sw_priv *priv = irq_data_get_irq_chip_data(d);
+
+	priv->irq_mask = AR9331_SW_GINT_PHY_INT;
+}
+
+static void ar9331_sw_irq_bus_lock(struct irq_data *d)
+{
+	struct ar9331_sw_priv *priv = irq_data_get_irq_chip_data(d);
+
+	mutex_lock(&priv->lock_irq);
+}
+
+static void ar9331_sw_irq_bus_sync_unlock(struct irq_data *d)
 {
 	struct ar9331_sw_priv *priv = irq_data_get_irq_chip_data(d);
 	struct regmap *regmap = priv->regmap;
 	int ret;
 
 	ret = regmap_update_bits(regmap, AR9331_SW_REG_GINT_MASK,
-				 AR9331_SW_GINT_PHY_INT,
-				 AR9331_SW_GINT_PHY_INT);
+				 AR9331_SW_GINT_PHY_INT, priv->irq_mask);
 	if (ret)
-		dev_err(priv->dev, "could not unmask IRQ\n");
+		dev_err(priv->dev, "failed to change IRQ mask\n");
+
+	mutex_unlock(&priv->lock_irq);
 }
 
 static struct irq_chip ar9331_sw_irq_chip = {
 	.name = AR9331_SW_NAME,
 	.irq_mask = ar9331_sw_mask_irq,
 	.irq_unmask = ar9331_sw_unmask_irq,
+	.irq_bus_lock = ar9331_sw_irq_bus_lock,
+	.irq_bus_sync_unlock = ar9331_sw_irq_bus_sync_unlock,
 };
 
 static int ar9331_sw_irq_map(struct irq_domain *domain, unsigned int irq,
@@ -584,6 +598,7 @@ static int ar9331_sw_irq_init(struct ar9331_sw_priv *priv)
 		return irq ? irq : -EINVAL;
 	}
 
+	mutex_init(&priv->lock_irq);
 	ret = devm_request_threaded_irq(dev, irq, NULL, ar9331_sw_irq,
 					IRQF_ONESHOT, AR9331_SW_NAME, priv);
 	if (ret) {