Some atypical users of xhci-pci might need to manually reset their xHCI
controller before starting the HCD setup. Check if a reset controller
device is available to the PCI bus and trigger a reset.

Signed-off-by: Nicolas Saenz Julienne <redacted>

---

Changes since v2:
 - Also reset on resume

Changes since v1:
 - Use proper reset API
 - Make code simpler

 drivers/usb/host/xhci-pci.c | 10 ++++++++++
 drivers/usb/host/xhci.h     |  2 ++
 2 files changed, 12 insertions(+)

diff --git a/drivers/usb/host/xhci-pci.c b/drivers/usb/host/xhci-pci.c
index ef513c2fb843..e76b9283faa3 100644
--- a/drivers/usb/host/xhci-pci.c
+++ b/drivers/usb/host/xhci-pci.c

@@ -12,6 +12,7 @@
 #include <linux/slab.h>
 #include <linux/module.h>
 #include <linux/acpi.h>
+#include <linux/reset.h>
 
 #include "xhci.h"
 #include "xhci-trace.h"

@@ -339,6 +340,7 @@ static int xhci_pci_probe(struct pci_dev *dev, const struct pci_device_id *id)
 	struct xhci_hcd *xhci;
 	struct usb_hcd *hcd;
 	struct xhci_driver_data *driver_data;
+	struct reset_control *reset;
 
 	driver_data = (struct xhci_driver_data *)id->driver_data;
 	if (driver_data && driver_data->quirks & XHCI_RENESAS_FW_QUIRK) {

@@ -347,6 +349,11 @@ static int xhci_pci_probe(struct pci_dev *dev, const struct pci_device_id *id)
 			return retval;
 	}
 
+	reset = devm_reset_control_get_optional_exclusive(&dev->bus->dev, NULL);
+	if (IS_ERR(reset))
+		return PTR_ERR(reset);
+	reset_control_reset(reset);