[PATCH 1/2] xhci: Introduce "disable-usb3" DT property/quirk

[Sam Edwards <cfsworks@gmail.com>]

Some systems may have xHCI controllers that enumerate USB 3.0 ports, but
these ports nevertheless cannot be used. Perhaps enabling them triggers a
hardware bug, or perhaps they simply aren't connected and it would be
confusing to the user to see an unusable USB 3.0 rhub show up -- whatever
the case may be, it's reasonable to want to disable these ports.

Add a DT property (and associated quirk) to the xHCI driver that skips
over (i.e. ignores and doesn't initialize) any USB 3.0 ports discovered
during driver initialization.

Signed-off-by: Sam Edwards <CFSworks@gmail.com>
---
 Documentation/devicetree/bindings/usb/usb-xhci.yaml | 4 ++++
 drivers/usb/host/xhci-mem.c                         | 4 ++++
 drivers/usb/host/xhci-plat.c                        | 3 +++
 drivers/usb/host/xhci.h                             | 1 +
 4 files changed, 12 insertions(+)

diff --git a/Documentation/devicetree/bindings/usb/usb-xhci.yaml b/Documentation/devicetree/bindings/usb/usb-xhci.yaml
index 180a261c3e8f..8a64e747260a 100644
--- a/Documentation/devicetree/bindings/usb/usb-xhci.yaml
+++ b/Documentation/devicetree/bindings/usb/usb-xhci.yaml
@@ -25,6 +25,10 @@ properties:
     description: Set if the controller has broken port disable mechanism
     type: boolean
 
+  disable-usb3:
+    description: Ignore (don't initialize, don't use) USB3 ports
+    type: boolean
+
   imod-interval-ns:
     description: Interrupt moderation interval
     default: 5000
diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c
index 0a37f0d511cf..bf8fcab626e4 100644
--- a/drivers/usb/host/xhci-mem.c
+++ b/drivers/usb/host/xhci-mem.c
@@ -1968,6 +1968,10 @@ static void xhci_add_in_port(struct xhci_hcd *xhci, unsigned int num_ports,
 	minor_revision = XHCI_EXT_PORT_MINOR(temp);
 
 	if (major_revision == 0x03) {
+		/* Ignore USB3 ports entirely if USB3 support is disabled. */
+		if (xhci->quirks & XHCI_DISABLE_USB3)
+			return;
+
 		rhub = &xhci->usb3_rhub;
 		/*
 		 * Some hosts incorrectly use sub-minor version for minor
diff --git a/drivers/usb/host/xhci-plat.c b/drivers/usb/host/xhci-plat.c
index b93161374293..75285fb5bbbc 100644
--- a/drivers/usb/host/xhci-plat.c
+++ b/drivers/usb/host/xhci-plat.c
@@ -249,6 +249,9 @@ int xhci_plat_probe(struct platform_device *pdev, struct device *sysdev, const s
 		if (device_property_read_bool(tmpdev, "quirk-broken-port-ped"))
 			xhci->quirks |= XHCI_BROKEN_PORT_PED;
 
+		if (device_property_read_bool(tmpdev, "disable-usb3"))
+			xhci->quirks |= XHCI_DISABLE_USB3;
+
 		device_property_read_u32(tmpdev, "imod-interval-ns",
 					 &xhci->imod_interval);
 	}
diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h
index 5df370482521..c53fbeea478f 100644
--- a/drivers/usb/host/xhci.h
+++ b/drivers/usb/host/xhci.h
@@ -1906,6 +1906,7 @@ struct xhci_hcd {
 #define XHCI_RESET_TO_DEFAULT	BIT_ULL(44)
 #define XHCI_ZHAOXIN_TRB_FETCH	BIT_ULL(45)
 #define XHCI_ZHAOXIN_HOST	BIT_ULL(46)
+#define XHCI_DISABLE_USB3	BIT_ULL(47)
 
 	unsigned int		num_active_eps;
 	unsigned int		limit_active_eps;
-- 
2.41.0