From 0cfbd328d60f85b0dcf66df61a3615e9a8e5d4e4 Mon Sep 17 00:00:00 2001 From: Michal Sojka Date: Wed, 24 Sep 2014 22:43:21 +0200 Subject: usb: Add LED triggers for USB activity MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit With this patch, USB activity can be signaled by blinking a LED. There are two triggers, one for activity on USB host and one for USB gadget. Both triggers should work with all host/device controllers. Tested only with musb. Performace: I measured performance overheads on ARM Cortex-A8 (TI AM335x) running on 600 MHz. Duration of usb_led_activity(): - with no LED attached to the trigger: 2 ± 1 µs - with one GPIO LED attached to the trigger: 2 ± 1 µs or 8 ± 2 µs (two peaks in histogram) Duration of functions calling usb_led_activity() (with this patch applied and no LED attached to the trigger): - __usb_hcd_giveback_urb(): 10 - 25 µs - usb_gadget_giveback_request(): 2 - 6 µs Signed-off-by: Michal Sojka Acked-by: Felipe Balbi Tested-by: Felipe Balbi Signed-off-by: Greg Kroah-Hartman --- drivers/usb/core/hcd.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'drivers/usb/core') diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c index d3fe161..bcb96ff 100644 --- a/drivers/usb/core/hcd.c +++ b/drivers/usb/core/hcd.c @@ -1664,6 +1664,8 @@ static void __usb_hcd_giveback_urb(struct urb *urb) usbmon_urb_complete(&hcd->self, urb, status); usb_anchor_suspend_wakeups(anchor); usb_unanchor_urb(urb); + if (likely(status == 0)) + usb_led_activity(USB_LED_EVENT_HOST); /* pass ownership to the completion handler */ urb->status = status; -- cgit v1.1