usb: xhci: Correct last context entry calculation for Configure Endpoint

The current XHCI driver recalculates the Context Entries field in the
Slot Context on every add_endpoint() and drop_endpoint() call. In the
case of drop_endpoint(), it seems to assume that the add_flags will
always contain every endpoint for the new configuration, which is not
necessarily correct if you don't make assumptions about how the USB core
uses the add_endpoint/drop_endpoint interface (add_flags only contains
endpoints that are new additions in the new configuration).

Furthermore, EP0_FLAG is not consistently set in add_flags throughout
the lifetime of a device. This means that when all endpoints are
dropped, the Context Entries field can be set to 0 (which is invalid and
may cause a Parameter Error) or -1 (which is interpreted as 31 and
causes the driver to keep using the old, incorrect value).

The only surefire way to set this field right is to also take all
existing endpoints into account, and to force the value to 1 (meaning
only EP0 is active) if no other endpoint is found. This patch implements
that as a single step in the final check_bandwidth() call and removes
the intermediary calculations from add_endpoint() and drop_endpoint().

Signed-off-by: Julius Werner <jwerner@chromium.org>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/xhci.c

@@ -1582,12 +1582,10 @@ int xhci_drop_endpoint(struct usb_hcd *hcd, struct usb_device *udev,
 	struct xhci_hcd *xhci;
 	struct xhci_container_ctx *in_ctx, *out_ctx;
 	struct xhci_input_control_ctx *ctrl_ctx;
-	struct xhci_slot_ctx *slot_ctx;
-	unsigned int last_ctx;
 	unsigned int ep_index;
 	struct xhci_ep_ctx *ep_ctx;
 	u32 drop_flag;
-	u32 new_add_flags, new_drop_flags, new_slot_info;
+	u32 new_add_flags, new_drop_flags;
 	int ret;
 
 	ret = xhci_check_args(hcd, udev, ep, 1, true, __func__);
@@ -1634,24 +1632,13 @@ int xhci_drop_endpoint(struct usb_hcd *hcd, struct usb_device *udev,
 	ctrl_ctx->add_flags &= cpu_to_le32(~drop_flag);
 	new_add_flags = le32_to_cpu(ctrl_ctx->add_flags);
 
-	last_ctx = xhci_last_valid_endpoint(le32_to_cpu(ctrl_ctx->add_flags));
-	slot_ctx = xhci_get_slot_ctx(xhci, in_ctx);
-	/* Update the last valid endpoint context, if we deleted the last one */
-	if ((le32_to_cpu(slot_ctx->dev_info) & LAST_CTX_MASK) >
-	    LAST_CTX(last_ctx)) {
-		slot_ctx->dev_info &= cpu_to_le32(~LAST_CTX_MASK);
-		slot_ctx->dev_info |= cpu_to_le32(LAST_CTX(last_ctx));
-	}
-	new_slot_info = le32_to_cpu(slot_ctx->dev_info);
-
 	xhci_endpoint_zero(xhci, xhci->devs[udev->slot_id], ep);
 
-	xhci_dbg(xhci, "drop ep 0x%x, slot id %d, new drop flags = %#x, new add flags = %#x, new slot info = %#x\n",
+	xhci_dbg(xhci, "drop ep 0x%x, slot id %d, new drop flags = %#x, new add flags = %#x\n",
 			(unsigned int) ep->desc.bEndpointAddress,
 			udev->slot_id,
 			(unsigned int) new_drop_flags,
-			(unsigned int) new_add_flags,
-			(unsigned int) new_slot_info);
+			(unsigned int) new_add_flags);
 	return 0;
 }
 
@@ -1674,11 +1661,9 @@ int xhci_add_endpoint(struct usb_hcd *hcd, struct usb_device *udev,
 	struct xhci_hcd *xhci;
 	struct xhci_container_ctx *in_ctx, *out_ctx;
 	unsigned int ep_index;
-	struct xhci_slot_ctx *slot_ctx;
 	struct xhci_input_control_ctx *ctrl_ctx;
 	u32 added_ctxs;
-	unsigned int last_ctx;
-	u32 new_add_flags, new_drop_flags, new_slot_info;
+	u32 new_add_flags, new_drop_flags;
 	struct xhci_virt_device *virt_dev;
 	int ret = 0;
 
@@ -1693,7 +1678,6 @@ int xhci_add_endpoint(struct usb_hcd *hcd, struct usb_device *udev,
 		return -ENODEV;
 
 	added_ctxs = xhci_get_endpoint_flag(&ep->desc);
-	last_ctx = xhci_last_valid_endpoint(added_ctxs);
 	if (added_ctxs == SLOT_FLAG || added_ctxs == EP0_FLAG) {
 		/* FIXME when we have to issue an evaluate endpoint command to
 		 * deal with ep0 max packet size changing once we get the
@@ -1759,24 +1743,14 @@ int xhci_add_endpoint(struct usb_hcd *hcd, struct usb_device *udev,
 	 */
 	new_drop_flags = le32_to_cpu(ctrl_ctx->drop_flags);
 
-	slot_ctx = xhci_get_slot_ctx(xhci, in_ctx);
-	/* Update the last valid endpoint context, if we just added one past */
-	if ((le32_to_cpu(slot_ctx->dev_info) & LAST_CTX_MASK) <
-	    LAST_CTX(last_ctx)) {
-		slot_ctx->dev_info &= cpu_to_le32(~LAST_CTX_MASK);
-		slot_ctx->dev_info |= cpu_to_le32(LAST_CTX(last_ctx));
-	}
-	new_slot_info = le32_to_cpu(slot_ctx->dev_info);
-
 	/* Store the usb_device pointer for later use */
 	ep->hcpriv = udev;
 
-	xhci_dbg(xhci, "add ep 0x%x, slot id %d, new drop flags = %#x, new add flags = %#x, new slot info = %#x\n",
+	xhci_dbg(xhci, "add ep 0x%x, slot id %d, new drop flags = %#x, new add flags = %#x\n",
 			(unsigned int) ep->desc.bEndpointAddress,
 			udev->slot_id,
 			(unsigned int) new_drop_flags,
-			(unsigned int) new_add_flags,
-			(unsigned int) new_slot_info);
+			(unsigned int) new_add_flags);
 	return 0;
 }
 
@@ -2746,8 +2720,19 @@ int xhci_check_bandwidth(struct usb_hcd *hcd, struct usb_device *udev)
 		ret = 0;
 		goto command_cleanup;
 	}
-	xhci_dbg(xhci, "New Input Control Context:\n");
+	/* Fix up Context Entries field. Minimum value is EP0 == BIT(1). */
 	slot_ctx = xhci_get_slot_ctx(xhci, virt_dev->in_ctx);
+	for (i = 31; i >= 1; i--) {
+		__le32 le32 = cpu_to_le32(BIT(i));
+
+		if ((virt_dev->eps[i-1].ring && !(ctrl_ctx->drop_flags & le32))
+		    || (ctrl_ctx->add_flags & le32) || i == 1) {
+			slot_ctx->dev_info &= cpu_to_le32(~LAST_CTX_MASK);
+			slot_ctx->dev_info |= cpu_to_le32(LAST_CTX(i));
+			break;
+		}
+	}
+	xhci_dbg(xhci, "New Input Control Context:\n");
 	xhci_dbg_ctx(xhci, virt_dev->in_ctx,
 		     LAST_CTX_TO_EP_NUM(le32_to_cpu(slot_ctx->dev_info)));