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usb: Add LED triggers for USB activity

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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>
This commit is contained in:
Michal Sojka
2014-09-24 22:43:21 +02:00
committed by Greg Kroah-Hartman
parent aa923ef1aa
commit 0cfbd328d6
6 changed files with 86 additions and 0 deletions
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57
drivers/usb/common/led.c Normal file
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/*
* LED Triggers for USB Activity
*
* Copyright 2014 Michal Sojka <sojka@merica.cz>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
*/
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/leds.h>
#include <linux/usb.h>
#define BLINK_DELAY 30
static unsigned long usb_blink_delay = BLINK_DELAY;
DEFINE_LED_TRIGGER(ledtrig_usb_gadget);
DEFINE_LED_TRIGGER(ledtrig_usb_host);
void usb_led_activity(enum usb_led_event ev)
{
struct led_trigger *trig = NULL;
switch (ev) {
case USB_LED_EVENT_GADGET:
trig = ledtrig_usb_gadget;
break;
case USB_LED_EVENT_HOST:
trig = ledtrig_usb_host;
break;
}
/* led_trigger_blink_oneshot() handles trig == NULL gracefully */
led_trigger_blink_oneshot(trig, &usb_blink_delay, &usb_blink_delay, 0);
}
EXPORT_SYMBOL_GPL(usb_led_activity);
static int __init ledtrig_usb_init(void)
{
led_trigger_register_simple("usb-gadget", &ledtrig_usb_gadget);
led_trigger_register_simple("usb-host", &ledtrig_usb_host);
return 0;
}
static void __exit ledtrig_usb_exit(void)
{
led_trigger_unregister_simple(ledtrig_usb_gadget);
led_trigger_unregister_simple(ledtrig_usb_host);
}
module_init(ledtrig_usb_init);
module_exit(ledtrig_usb_exit);