usb: hcd: add OTG ID signal sensing

On the Renesas R8A7791 SoC based boards there's MAX3355 USB OTG chip and mini-AB USB connector corresponding to USB port 0 driven either by EHCI/OHCI or Renesas USBHS gadget controller. And we'd like the host/gadget drivers to work based on the cable type connected. An 'extcon' driver for MAX3355 has been written, so we only need to bind to it via device tree which I'm doing in this patch.

I wasn't able to find a solution better than checking the cable type at the host driver probe time and refusing to drive a host if B-cable is connected.

Signed-off-by Sergei Shtylyov <[email protected]>

---
The patch is against the 'usb-next' branch of Greg KH's 'usb.git' repo. It needs the recent 'extcon' core in order to properly handle probe deferral.

 drivers/usb/core/hcd.c |   18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

Index: usb/drivers/usb/core/hcd.c
==============================
===> --- usb.orig/drivers/usb/core/hcd.c
+++ usb/drivers/usb/core/hcd.c

(quoted diff) +18 -0

@@ -42,6 +42,7 @@
 #include <linux/pm_runtime.h>
 #include <linux/types.h>
 
+#include <linux/extcon.h>
 #include <linux/phy/phy.h>
 #include <linux/usb.h>
 #include <linux/usb/hcd.h>

@@ -2632,6 +2633,23 @@ int usb_add_hcd(struct usb_hcd *hcd,
 	int retval;
 	struct usb_device *rhdev;
 
+	if (IS_ENABLED(CONFIG_EXTCON) &&
+	    of_property_read_bool(hcd->self.controller->of_node, "extcon")) {
+		struct extcon_dev *edev;
+
+		edev = extcon_get_edev_by_phandle(hcd->self.controller, 0);
+		if (IS_ERR(edev))
+			return PTR_ERR(edev);
+
+		retval = extcon_get_cable_state(edev, "USB-HOST");
+		if (!retval) {
+			dev_err(hcd->self.controller,
+				"OTG B-cable plugged in, host driver won't
 load\n");
+			return -EINVAL;
+		} else if (retval < 0)
+			return retval;
+	}
+
 	if (IS_ENABLED(CONFIG_USB_PHY) && !hcd->usb_phy) {
 		struct usb_phy *phy = usb_get_phy_dev(hcd->self.controller,

0);

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Quoted 6 lines

On the Renesas R8A7791 SoC based boards there's MAX3355 USB OTG chip and mini-AB USB connector corresponding to USB port 0 driven either by EHCI/OHCI or Renesas USBHS gadget controller. And we'd like the host/gadget drivers to work based on the cable type connected. An 'extcon' driver for MAX3355 has been written, so we only need to bind to it via device tree which I'm doing in this patch.

Quoted 2 lines

I wasn't able to find a solution better than checking the cable type at the host driver probe time and refusing to drive a host if B-cable is connected.

You may need a dual-role/otg driver to do it, which can enable host/device function according to ID pin.