Commit 1cbd53c8 authored by Richard Leitner's avatar Richard Leitner Committed by Greg Kroah-Hartman
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usb: core: introduce per-port over-current counters 



For some userspace applications information on the number of
over-current conditions at specific USB hub ports is relevant.

In our case we have a series of USB hardware (using the cp210x driver)
which communicates using a proprietary protocol. These devices sometimes
trigger an over-current situation on some hubs. In case of such an
over-current situation the USB devices offer an interface for reducing
the max used power. As these conditions are quite rare and imply
performance reductions of the device we don't want to reduce the max
power always.

Therefore give user-space applications the possibility to react
adequately by introducing an over_current_counter in the usb port struct
which is exported via sysfs.

Signed-off-by: default avatarRichard Leitner <richard.leitner@skidata.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent e3cb7bde

Documentation/ABI/testing/sysfs-bus-usb

+10 −0
Original line number Diff line number Diff line
@@ -189,6 +189,16 @@ Description: 
		The file will read "hotplug", "wired" and "not used" if the

		information is available, and "unknown" otherwise.



What:		/sys/bus/usb/devices/.../(hub interface)/portX/over_current_count

Date:		February 2018

Contact:	Richard Leitner <richard.leitner@skidata.com>

Description:

		Most hubs are able to detect over-current situations on their

		ports and report them to the kernel. This attribute is to expose

		the number of over-current situation occurred on a specific port

		to user space. This file will contain an unsigned 32 bit value

		which wraps to 0 after its maximum is reached.



What:		/sys/bus/usb/devices/.../(hub interface)/portX/usb3_lpm_permit

Date:		November 2015

Contact:	Lu Baolu <baolu.lu@linux.intel.com>

drivers/usb/core/hub.c

+3 −1
Original line number Diff line number Diff line
@@ -5104,8 +5104,10 @@ static void port_event(struct usb_hub *hub, int port1) 


	if (portchange & USB_PORT_STAT_C_OVERCURRENT) {

		u16 status = 0, unused;

		port_dev->over_current_count++;



		dev_dbg(&port_dev->dev, "over-current change\n");

		dev_dbg(&port_dev->dev, "over-current change #%u\n",

			port_dev->over_current_count);

		usb_clear_port_feature(hdev, port1,

				USB_PORT_FEAT_C_OVER_CURRENT);

		msleep(100);	/* Cool down */

drivers/usb/core/hub.h

+1 −0
Original line number Diff line number Diff line
@@ -96,6 +96,7 @@ struct usb_port { 
	enum usb_port_connect_type connect_type;

	usb_port_location_t location;

	struct mutex status_lock;

	u32 over_current_count;

	u8 portnum;

	unsigned int is_superspeed:1;

	unsigned int usb3_lpm_u1_permit:1;

drivers/usb/core/port.c

+10 −0
Original line number Diff line number Diff line
@@ -41,6 +41,15 @@ static ssize_t connect_type_show(struct device *dev, 
}

static DEVICE_ATTR_RO(connect_type);



static ssize_t over_current_count_show(struct device *dev,

				       struct device_attribute *attr, char *buf)

{

	struct usb_port *port_dev = to_usb_port(dev);



	return sprintf(buf, "%u\n", port_dev->over_current_count);

}

static DEVICE_ATTR_RO(over_current_count);



static ssize_t usb3_lpm_permit_show(struct device *dev,

			      struct device_attribute *attr, char *buf)

{
@@ -109,6 +118,7 @@ static DEVICE_ATTR_RW(usb3_lpm_permit); 


static struct attribute *port_dev_attrs[] = {

	&dev_attr_connect_type.attr,

	&dev_attr_over_current_count.attr,

	NULL,

};

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