phy: rcar-gen3-usb2: fix mutex_lock calling in interrupt

This patch fixes an issue that the extcon_set_cable_state_() is possible
to cause "BUG: scheduling while atomic" because this driver calls
extcon_set_cable_state_() in the interrupt handler and mutex_lock()
is possible to be called by like the following call trace.
So, this patch adds a workqueue function to resolve this issue.

[    9.706504] BUG: scheduling while atomic: systemd-journal/25893/0x00010303
[    9.714569] Modules linked in:
[    9.717629] CPU: 0 PID: 25893 Comm: systemd-journal Not tainted 4.7.0-rc4+ #86
[    9.724844] Hardware name: Renesas Salvator-X board based on r8a7795 (DT)
[    9.731624] Call trace:
[    9.734077] [<ffff0000080889f0>] dump_backtrace+0x0/0x1a8
[    9.739470] [<ffff000008088bac>] show_stack+0x14/0x20
[    9.744520] [<ffff000008348ab4>] dump_stack+0x94/0xb8
[    9.749568] [<ffff0000080da18c>] __schedule_bug+0x44/0x58
[    9.754966] [<ffff0000087c6394>] __schedule+0x4e4/0x598
[    9.760185] [<ffff0000087c6484>] schedule+0x3c/0xa8
[    9.765057] [<ffff0000087c6928>] schedule_preempt_disabled+0x20/0x38
[    9.771408] [<ffff0000080f20dc>] mutex_optimistic_spin+0x18c/0x1d0
[    9.777583] [<ffff0000087c7ef0>] __mutex_lock_slowpath+0x38/0x140
[    9.783669] [<ffff0000087c803c>] mutex_lock+0x44/0x60
[    9.788717] [<ffff00000834ca48>] kobject_uevent_env+0x250/0x500
[    9.794634] [<ffff0000086ae8c0>] extcon_update_state+0x220/0x298
[    9.800634] [<ffff0000086ae9d8>] extcon_set_cable_state_+0x78/0x88
[    9.806812] [<ffff000008376004>] rcar_gen3_device_recognition+0x5c/0xe0
[    9.813420] [<ffff0000083761bc>] rcar_gen3_phy_usb2_irq+0x3c/0x48
[    9.819509] [<ffff0000080fae94>] handle_irq_event_percpu+0x94/0x140
[    9.825769] [<ffff0000080faf88>] handle_irq_event+0x48/0x78
[    9.831334] [<ffff0000080fe620>] handle_fasteoi_irq+0xb8/0x1b0
[    9.837162] [<ffff0000080fa3c4>] generic_handle_irq+0x24/0x38
[    9.842900] [<ffff0000080fa6fc>] __handle_domain_irq+0x5c/0xb8
[    9.848727] [<ffff000008081520>] gic_handle_irq+0x58/0xb0

Reported-by: Simon Horman <horms@verge.net.au>
Fixes: 2b38543c8db1 ("phy: rcar-gen3-usb2: add extcon support")
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>

drivers/phy/phy-rcar-gen3-usb2.c

@@ -21,6 +21,7 @@
 #include <linux/phy/phy.h>
 #include <linux/platform_device.h>
 #include <linux/regulator/consumer.h>
+#include <linux/workqueue.h>
 
 /******* USB2.0 Host registers (original offset is +0x200) *******/
 #define USB2_INT_ENABLE		0x000
@@ -81,9 +82,25 @@ struct rcar_gen3_chan {
 	struct extcon_dev *extcon;
 	struct phy *phy;
 	struct regulator *vbus;
+	struct work_struct work;
+	bool extcon_host;
 	bool has_otg;
 };
 
+static void rcar_gen3_phy_usb2_work(struct work_struct *work)
+{
+	struct rcar_gen3_chan *ch = container_of(work, struct rcar_gen3_chan,
+						 work);
+
+	if (ch->extcon_host) {
+		extcon_set_cable_state_(ch->extcon, EXTCON_USB_HOST, true);
+		extcon_set_cable_state_(ch->extcon, EXTCON_USB, false);
+	} else {
+		extcon_set_cable_state_(ch->extcon, EXTCON_USB_HOST, false);
+		extcon_set_cable_state_(ch->extcon, EXTCON_USB, true);
+	}
+}
+
 static void rcar_gen3_set_host_mode(struct rcar_gen3_chan *ch, int host)
 {
 	void __iomem *usb2_base = ch->base;
@@ -130,8 +147,8 @@ static void rcar_gen3_init_for_host(struct rcar_gen3_chan *ch)
 	rcar_gen3_set_host_mode(ch, 1);
 	rcar_gen3_enable_vbus_ctrl(ch, 1);
 
-	extcon_set_cable_state_(ch->extcon, EXTCON_USB_HOST, true);
-	extcon_set_cable_state_(ch->extcon, EXTCON_USB, false);
+	ch->extcon_host = true;
+	schedule_work(&ch->work);
 }
 
 static void rcar_gen3_init_for_peri(struct rcar_gen3_chan *ch)
@@ -140,8 +157,8 @@ static void rcar_gen3_init_for_peri(struct rcar_gen3_chan *ch)
 	rcar_gen3_set_host_mode(ch, 0);
 	rcar_gen3_enable_vbus_ctrl(ch, 0);
 
-	extcon_set_cable_state_(ch->extcon, EXTCON_USB_HOST, false);
-	extcon_set_cable_state_(ch->extcon, EXTCON_USB, true);
+	ch->extcon_host = false;
+	schedule_work(&ch->work);
 }
 
 static bool rcar_gen3_check_id(struct rcar_gen3_chan *ch)
@@ -301,6 +318,7 @@ static int rcar_gen3_phy_usb2_probe(struct platform_device *pdev)
 	if (irq >= 0) {
 		int ret;
 
+		INIT_WORK(&channel->work, rcar_gen3_phy_usb2_work);
 		irq = devm_request_irq(dev, irq, rcar_gen3_phy_usb2_irq,
 				       IRQF_SHARED, dev_name(dev), channel);
 		if (irq < 0)