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authorMichal Sojka <sojka@merica.cz>2014-09-25 00:43:21 +0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-09-25 19:05:12 +0400
commit0cfbd328d60f85b0dcf66df61a3615e9a8e5d4e4 (patch)
treebae04eca569eecee711f27fd2e1d08e6f837ebbe /drivers/usb/common
parentaa923ef1aa39473b7d1f413c73a3e1d19ebde65d (diff)
downloadlinux-0cfbd328d60f85b0dcf66df61a3615e9a8e5d4e4.tar.xz
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>
Diffstat (limited to 'drivers/usb/common')
-rw-r--r--drivers/usb/common/Makefile1
-rw-r--r--drivers/usb/common/led.c57
2 files changed, 58 insertions, 0 deletions
diff --git a/drivers/usb/common/Makefile b/drivers/usb/common/Makefile
index 052c12069c24..ca2f8bd0e431 100644
--- a/drivers/usb/common/Makefile
+++ b/drivers/usb/common/Makefile
@@ -4,5 +4,6 @@
obj-$(CONFIG_USB_COMMON) += usb-common.o
usb-common-y += common.o
+usb-common-$(CONFIG_USB_LED_TRIG) += led.o
obj-$(CONFIG_USB_OTG_FSM) += usb-otg-fsm.o
diff --git a/drivers/usb/common/led.c b/drivers/usb/common/led.c
new file mode 100644
index 000000000000..df23da00a901
--- /dev/null
+++ b/drivers/usb/common/led.c
@@ -0,0 +1,57 @@
+/*
+ * 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);