usb: gadget: tegra-xudc: fix PM use count underflow

Upon resume from system suspend, the PM runtime core issues the
following warning:

tegra-xudc 3550000.usb: Runtime PM usage count underflow!

This is because tegra_xudc_resume() unconditionally calls
schedule_work(&xudc->usb_role_sw_work) whether or not anything has
changed, which causes tegra_xudc_device_mode_off() to be called
even when we're already in that mode.

Keep track of the current state of "device_mode", and only schedule
this work if it has changed from the hardware state on resume.

Signed-off-by: "Russell King (Oracle)" <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: Russell King (Oracle)

drivers/usb/gadget/udc/tegra-xudc.c

@@ -502,6 +502,7 @@ struct tegra_xudc {
 	struct clk_bulk_data *clks;
 
 	bool device_mode;
+	bool current_device_mode;
 	struct work_struct usb_role_sw_work;
 
 	struct phy **usb3_phy;
@@ -715,6 +716,8 @@ static void tegra_xudc_device_mode_on(struct tegra_xudc *xudc)
 
 	phy_set_mode_ext(xudc->curr_utmi_phy, PHY_MODE_USB_OTG,
 			 USB_ROLE_DEVICE);
+
+	xudc->current_device_mode = true;
 }
 
 static void tegra_xudc_device_mode_off(struct tegra_xudc *xudc)
@@ -725,6 +728,8 @@ static void tegra_xudc_device_mode_off(struct tegra_xudc *xudc)
 
 	dev_dbg(xudc->dev, "device mode off\n");
 
+	xudc->current_device_mode = false;
+
 	connected = !!(xudc_readl(xudc, PORTSC) & PORTSC_CCS);
 
 	reinit_completion(&xudc->disconnect_complete);
@@ -4044,10 +4049,10 @@ static int __maybe_unused tegra_xudc_resume(struct device *dev)
 
 	spin_lock_irqsave(&xudc->lock, flags);
 	xudc->suspended = false;
+	if (xudc->device_mode != xudc->current_device_mode)
+		schedule_work(&xudc->usb_role_sw_work);
 	spin_unlock_irqrestore(&xudc->lock, flags);
 
-	schedule_work(&xudc->usb_role_sw_work);
-
 	pm_runtime_enable(dev);
 
 	return 0;