From 2dc3753997f3c80ce8b950242ab9bb3fb936acfd Mon Sep 17 00:00:00 2001 From: Sarah Sharp Date: Fri, 2 Sep 2011 11:05:40 -0700 Subject: [PATCH] xhci: If no endpoints changed, don't issue BW command. Some alternate interface settings have no endpoints associated with them. This shows up in some USB webcams, particularly the Logitech HD 1080p, which uses the uvcvideo driver. If a driver switches between two alt settings with no endpoints, there is no need to issue a configure endpoint command, because there is no endpoint information to update. The only time a configure endpoint command with just the add slot flag set makes sense is when the driver is updating hub characteristics in the slot context. However, that code never calls xhci_check_bandwidth, so we should be safe not issuing a command if only the slot context add flag is set. Signed-off-by: Sarah Sharp Signed-off-by: Greg Kroah-Hartman --- drivers/usb/host/xhci.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c index f647d918a886..fcc5821a27f3 100644 --- a/drivers/usb/host/xhci.c +++ b/drivers/usb/host/xhci.c @@ -1888,6 +1888,12 @@ int xhci_check_bandwidth(struct usb_hcd *hcd, struct usb_device *udev) ctrl_ctx->add_flags |= cpu_to_le32(SLOT_FLAG); ctrl_ctx->add_flags &= cpu_to_le32(~EP0_FLAG); ctrl_ctx->drop_flags &= cpu_to_le32(~(SLOT_FLAG | EP0_FLAG)); + + /* Don't issue the command if there's no endpoints to update. */ + if (ctrl_ctx->add_flags == cpu_to_le32(SLOT_FLAG) && + ctrl_ctx->drop_flags == 0) + return 0; + xhci_dbg(xhci, "New Input Control Context:\n"); slot_ctx = xhci_get_slot_ctx(xhci, virt_dev->in_ctx); xhci_dbg_ctx(xhci, virt_dev->in_ctx, -- 2.20.1