usb: dwc3: pci: Runtime resume child device from wq

Driver currently resumes and increments pm usage_count
of its child device (dwc3 main) from its runtime_resume
handler. This requires dwc3 runtime_resume to perform
pm_runtime_put to decrement the pm usage_count. However
runtime_put from dwc3 happens for non pci drivers
(e.g. dwc3-if-simple.c) as well which results in dwc3
pm usage_count becoming negative after couple of
runtime suspend resume iterations. Fix this by
performing runtime_get/put from dwc3-pci driver only
using workqueue.

Signed-off-by: Manu Gautam <mgautam@codeaurora.org>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/dwc3/core.c

@@ -1391,7 +1391,6 @@ static int dwc3_runtime_resume(struct device *dev)
 	}
 
 	pm_runtime_mark_last_busy(dev);
-	pm_runtime_put(dev);
 
 	return 0;
 }

drivers/usb/dwc3/dwc3-pci.c

@@ -20,6 +20,7 @@
 #include <linux/module.h>
 #include <linux/slab.h>
 #include <linux/pci.h>
+#include <linux/workqueue.h>
 #include <linux/pm_runtime.h>
 #include <linux/platform_device.h>
 #include <linux/gpio/consumer.h>
@@ -61,6 +62,7 @@ struct dwc3_pci {
 	guid_t guid;
 
 	unsigned int has_dsm_for_pm:1;
+	struct work_struct wakeup_work;
 };
 
 static const struct acpi_gpio_params reset_gpios = { 0, 0, false };
@@ -174,6 +176,22 @@ static int dwc3_pci_quirks(struct dwc3_pci *dwc)
 	return 0;
 }
 
+#ifdef CONFIG_PM
+static void dwc3_pci_resume_work(struct work_struct *work)
+{
+	struct dwc3_pci *dwc = container_of(work, struct dwc3_pci, wakeup_work);
+	struct platform_device *dwc3 = dwc->dwc3;
+	int ret;
+
+	ret = pm_runtime_get_sync(&dwc3->dev);
+	if (ret)
+		return;
+
+	pm_runtime_mark_last_busy(&dwc3->dev);
+	pm_runtime_put_sync_autosuspend(&dwc3->dev);
+}
+#endif
+
 static int dwc3_pci_probe(struct pci_dev *pci,
 		const struct pci_device_id *id)
 {
@@ -232,6 +250,9 @@ static int dwc3_pci_probe(struct pci_dev *pci,
 	device_init_wakeup(dev, true);
 	pci_set_drvdata(pci, dwc);
 	pm_runtime_put(dev);
+#ifdef CONFIG_PM
+	INIT_WORK(&dwc->wakeup_work, dwc3_pci_resume_work);
+#endif
 
 	return 0;
 err:
@@ -243,6 +264,9 @@ static void dwc3_pci_remove(struct pci_dev *pci)
 {
 	struct dwc3_pci		*dwc = pci_get_drvdata(pci);
 
+#ifdef CONFIG_PM
+	cancel_work_sync(&dwc->wakeup_work);
+#endif
 	device_init_wakeup(&pci->dev, false);
 	pm_runtime_get(&pci->dev);
 	platform_device_unregister(dwc->dwc3);
@@ -318,14 +342,15 @@ static int dwc3_pci_runtime_suspend(struct device *dev)
 static int dwc3_pci_runtime_resume(struct device *dev)
 {
 	struct dwc3_pci		*dwc = dev_get_drvdata(dev);
-	struct platform_device	*dwc3 = dwc->dwc3;
 	int			ret;
 
 	ret = dwc3_pci_dsm(dwc, PCI_INTEL_BXT_STATE_D0);
 	if (ret)
 		return ret;
 
-	return pm_runtime_get(&dwc3->dev);
+	queue_work(pm_wq, &dwc->wakeup_work);
+
+	return 0;
 }
 #endif /* CONFIG_PM */