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0cfbd328d6
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>
58 lines
1.3 KiB
C
58 lines
1.3 KiB
C
/*
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* LED Triggers for USB Activity
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*
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* Copyright 2014 Michal Sojka <sojka@merica.cz>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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*/
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#include <linux/module.h>
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#include <linux/kernel.h>
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#include <linux/init.h>
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#include <linux/leds.h>
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#include <linux/usb.h>
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#define BLINK_DELAY 30
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static unsigned long usb_blink_delay = BLINK_DELAY;
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DEFINE_LED_TRIGGER(ledtrig_usb_gadget);
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DEFINE_LED_TRIGGER(ledtrig_usb_host);
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void usb_led_activity(enum usb_led_event ev)
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{
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struct led_trigger *trig = NULL;
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switch (ev) {
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case USB_LED_EVENT_GADGET:
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trig = ledtrig_usb_gadget;
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break;
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case USB_LED_EVENT_HOST:
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trig = ledtrig_usb_host;
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break;
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}
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/* led_trigger_blink_oneshot() handles trig == NULL gracefully */
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led_trigger_blink_oneshot(trig, &usb_blink_delay, &usb_blink_delay, 0);
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}
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EXPORT_SYMBOL_GPL(usb_led_activity);
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static int __init ledtrig_usb_init(void)
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{
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led_trigger_register_simple("usb-gadget", &ledtrig_usb_gadget);
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led_trigger_register_simple("usb-host", &ledtrig_usb_host);
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return 0;
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}
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static void __exit ledtrig_usb_exit(void)
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{
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led_trigger_unregister_simple(ledtrig_usb_gadget);
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led_trigger_unregister_simple(ledtrig_usb_host);
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}
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module_init(ledtrig_usb_init);
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module_exit(ledtrig_usb_exit);
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