usb: xhci-pci: Add support for reset controllers

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.
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Acked-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Link: https://lore.kernel.org/r/20200629161845.6021-6-nsaenzjulienne@suse.deSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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"
@@ -346,6 +347,7 @@ 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) {
@@ -354,6 +356,11 @@ 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->dev, NULL);
+	if (IS_ERR(reset))
+		return PTR_ERR(reset);
+	reset_control_reset(reset);
+
 	/* Prevent runtime suspending between USB-2 and USB-3 initialization */
 	pm_runtime_get_noresume(&dev->dev);
 
@@ -371,6 +378,7 @@ static int xhci_pci_probe(struct pci_dev *dev, const struct pci_device_id *id)
 	/* USB 2.0 roothub is stored in the PCI device now. */
 	hcd = dev_get_drvdata(&dev->dev);
 	xhci = hcd_to_xhci(hcd);
+	xhci->reset = reset;
 	xhci->shared_hcd = usb_create_shared_hcd(&xhci_pci_hc_driver, &dev->dev,
 						 pci_name(dev), hcd);
 	if (!xhci->shared_hcd) {
@@ -522,6 +530,8 @@ static int xhci_pci_resume(struct usb_hcd *hcd, bool hibernated)
 	struct pci_dev		*pdev = to_pci_dev(hcd->self.controller);
 	int			retval = 0;
 
+	reset_control_reset(xhci->reset);
+
 	/* The BIOS on systems with the Intel Panther Point chipset may or may
 	 * not support xHCI natively.  That means that during system resume, it
 	 * may switch the ports back to EHCI so that users can use their

drivers/usb/host/xhci.h

@@ -1770,6 +1770,8 @@ struct xhci_hcd {
 	/* optional clocks */
 	struct clk		*clk;
 	struct clk		*reg_clk;
+	/* optional reset controller */
+	struct reset_control *reset;
 	/* data structures */
 	struct xhci_device_context_array *dcbaa;
 	struct xhci_ring	*cmd_ring;