usb: Add LED triggers for USB activity

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 <sojka@merica.cz>
Acked-by: Felipe Balbi <balbi@ti.com>
Tested-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 4 insertions, 0 deletions

diff --git a/drivers/usb/gadget/udc/udc-core.c b/drivers/usb/gadget/udc/udc-core.c
index 16d3f6f..f107bb6 100644
--- a/drivers/usb/gadget/udc/udc-core.c
+++ b/drivers/usb/gadget/udc/udc-core.c
@@ -27,6 +27,7 @@
 
 #include <linux/usb/ch9.h>
 #include <linux/usb/gadget.h>
+#include <linux/usb.h>
 
 /**
  * struct usb_udc - describes one usb device controller
@@ -116,6 +117,9 @@ EXPORT_SYMBOL_GPL(usb_gadget_unmap_request);
 void usb_gadget_giveback_request(struct usb_ep *ep,
 		struct usb_request *req)
 {
+	if (likely(req->status == 0))
+		usb_led_activity(USB_LED_EVENT_GADGET);
+
 	req->complete(ep, req);
 }
 EXPORT_SYMBOL_GPL(usb_gadget_giveback_request);