[PATCH 2/2] usb: dwc3: drd: Fix lock-up on ID change during system suspend/resume

[Roger Quadros]

Adding/removing host/gadget controller before .pm_complete()
causes a lock-up. Let's prevent any dual-role state change
between .pm_prepare() and .pm_complete() to fix this.

Signed-off-by: Roger Quadros <rogerq@xxxxxx>
---
 drivers/usb/dwc3/core.c | 31 +++++++++++++++++++++++++++++++
 drivers/usb/dwc3/core.h |  5 +++++
 drivers/usb/dwc3/drd.c  | 10 ++++++----
 3 files changed, 42 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
index 42379cc..85388dd 100644
--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -1414,6 +1414,33 @@ static int dwc3_runtime_idle(struct device *dev)
 #endif /* CONFIG_PM */
 
 #ifdef CONFIG_PM_SLEEP
+static int dwc3_prepare(struct device *dev)
+{
+	struct dwc3	*dwc = dev_get_drvdata(dev);
+	unsigned long	flags;
+
+	if (dwc->dr_mode == USB_DR_MODE_OTG) {
+		spin_lock_irqsave(&dwc->lock, flags);
+		dwc->dr_keep_role = true;
+		spin_unlock_irqrestore(&dwc->lock, flags);
+	}
+
+	return 0;
+}
+
+static void dwc3_complete(struct device *dev)
+{
+	struct dwc3	*dwc = dev_get_drvdata(dev);
+	unsigned long	flags;
+
+	if (dwc->dr_mode == USB_DR_MODE_OTG) {
+		spin_lock_irqsave(&dwc->lock, flags);
+		dwc->dr_keep_role = false;
+		spin_unlock_irqrestore(&dwc->lock, flags);
+		dwc3_drd_update(dwc);
+	}
+}
+
 static int dwc3_suspend(struct device *dev)
 {
 	struct dwc3	*dwc = dev_get_drvdata(dev);
@@ -1451,6 +1478,10 @@ static const struct dev_pm_ops dwc3_dev_pm_ops = {
 	SET_SYSTEM_SLEEP_PM_OPS(dwc3_suspend, dwc3_resume)
 	SET_RUNTIME_PM_OPS(dwc3_runtime_suspend, dwc3_runtime_resume,
 			dwc3_runtime_idle)
+#ifdef CONFIG_PM_SLEEP
+	.prepare = dwc3_prepare,
+	.complete = dwc3_complete,
+#endif
 };
 
 #ifdef CONFIG_OF
diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
index 4a4a4c9..f5eb474 100644
--- a/drivers/usb/dwc3/core.h
+++ b/drivers/usb/dwc3/core.h
@@ -786,6 +786,7 @@ struct dwc3_scratchpad_array {
  * @dr_mode: requested mode of operation
  * @current_dr_role: current role of operation when in dual-role mode
  * @desired_dr_role: desired role of operation when in dual-role mode
+ * @dr_keep_role: keep the current dual-role irrespective of ID changes
  * @edev: extcon handle
  * @edev_nb: extcon notifier
  * @hsphy_mode: UTMI phy mode, one of following:
@@ -901,6 +902,7 @@ struct dwc3 {
 	enum usb_dr_mode	dr_mode;
 	u32			current_dr_role;
 	u32			desired_dr_role;
+	bool			dr_keep_role;
 	struct extcon_dev	*edev;
 	struct notifier_block	edev_nb;
 	enum usb_phy_interface	hsphy_mode;
@@ -1227,11 +1229,14 @@ static inline int dwc3_send_gadget_generic_command(struct dwc3 *dwc,
 #if IS_ENABLED(CONFIG_USB_DWC3_DUAL_ROLE)
 int dwc3_drd_init(struct dwc3 *dwc);
 void dwc3_drd_exit(struct dwc3 *dwc);
+void dwc3_drd_update(struct dwc3 *dwc);
 #else
 static inline int dwc3_drd_init(struct dwc3 *dwc)
 { return 0; }
 static inline void dwc3_drd_exit(struct dwc3 *dwc)
 { }
+static inline void dwc3_drd_update(struct dwc3 *dwc);
+{ }
 #endif
 
 /* power management interface */
diff --git a/drivers/usb/dwc3/drd.c b/drivers/usb/dwc3/drd.c
index cc8ab9a..177a8be 100644
--- a/drivers/usb/dwc3/drd.c
+++ b/drivers/usb/dwc3/drd.c
@@ -13,7 +13,7 @@
 #include "core.h"
 #include "gadget.h"
 
-static void dwc3_drd_update(struct dwc3 *dwc)
+void dwc3_drd_update(struct dwc3 *dwc)
 {
 	int id;
 
@@ -31,9 +31,11 @@ static int dwc3_drd_notifier(struct notifier_block *nb,
 {
 	struct dwc3 *dwc = container_of(nb, struct dwc3, edev_nb);
 
-	dwc3_set_mode(dwc, event ?
-		      DWC3_GCTL_PRTCAP_HOST :
-		      DWC3_GCTL_PRTCAP_DEVICE);
+	if (!dwc->dr_keep_role) {
+		dwc3_set_mode(dwc, event ?
+			      DWC3_GCTL_PRTCAP_HOST :
+			      DWC3_GCTL_PRTCAP_DEVICE);
+	}
 
 	return NOTIFY_DONE;
 }
-- 
cheers,
-roger

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