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When the system suspends and a host controller's power is lost, the USB
core attempts to revive any USB devices that had the persist_enabled flag
set. For non-SuperSpeed devices, it will disable the port, and then set
the udev->reset_resume flag. This will cause the USB core to reset the
device, verify the device descriptors to make sure it's the same device,
and re-install any non-default configurations or alternate interface
settings.
However, we can't disable SuperSpeed root hub ports because that turns off
SuperSpeed terminations, which will inhibit any devices connecting at USB
3.0 speeds. (Plus external hubs don't allow SuperSpeed ports to be
disabled.)
Because of this logic in hub_activate():
/* We can forget about a "removed" device when there's a
* physical disconnect or the connect status changes.
*/
if (!(portstatus & USB_PORT_STAT_CONNECTION) ||
(portchange & USB_PORT_STAT_C_CONNECTION))
clear_bit(port1, hub->removed_bits);
if (!udev || udev->state == USB_STATE_NOTATTACHED) {
/* Tell khubd to disconnect the device or
* check for a new connection
*/
if (udev || (portstatus & USB_PORT_STAT_CONNECTION))
set_bit(port1, hub->change_bits);
} else if (portstatus & USB_PORT_STAT_ENABLE) {
/* The power session apparently survived the resume.
* If there was an overcurrent or suspend change
* (i.e., remote wakeup request), have khubd
* take care of it.
*/
if (portchange)
set_bit(port1, hub->change_bits);
} else if (udev->persist_enabled) {
udev->reset_resume = 1;
set_bit(port1, hub->change_bits);
} else {
/* The power session is gone; tell khubd */
usb_set_device_state(udev, USB_STATE_NOTATTACHED);
set_bit(port1, hub->change_bits);
}
a SuperSpeed device after a resume with a loss of power will never get the
reset_resume flag set. Instead the core will assume the power session
survived and that the device still has the same address, configuration,
and alternate interface settings. The xHCI host controller will have no
knowledge of the device (since all xhci_virt_devices were destroyed when
power loss was discovered, and xhci_discover_or_reset_device() has not
been called), and all URBs to the device will fail.
If the device driver responds by resetting the device, everything will
continue smoothly. However, if lsusb is used before the device driver
resets the device (or there is no driver), then all lsusb descriptor
fetches will fail.
The quick fix is to pretend the port is disabled in hub_activate(), by
clearing the local variable. But I'm not sure what other parts of the hub
driver need to be changed because they have assumptions about when ports
will be disabled.
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Signed-off-by: Andiry Xu <andiry.xu@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
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|---|---|---|
| .. | ||
| atm | ||
| c67x00 | ||
| class | ||
| core | ||
| early | ||
| gadget | ||
| host | ||
| image | ||
| misc | ||
| mon | ||
| musb | ||
| otg | ||
| serial | ||
| storage | ||
| wusbcore | ||
| Kconfig | ||
| Makefile | ||
| README | ||
| usb-skeleton.c | ||
To understand all the Linux-USB framework, you'll use these resources:
* This source code. This is necessarily an evolving work, and
includes kerneldoc that should help you get a current overview.
("make pdfdocs", and then look at "usb.pdf" for host side and
"gadget.pdf" for peripheral side.) Also, Documentation/usb has
more information.
* The USB 2.0 specification (from www.usb.org), with supplements
such as those for USB OTG and the various device classes.
The USB specification has a good overview chapter, and USB
peripherals conform to the widely known "Chapter 9".
* Chip specifications for USB controllers. Examples include
host controllers (on PCs, servers, and more); peripheral
controllers (in devices with Linux firmware, like printers or
cell phones); and hard-wired peripherals like Ethernet adapters.
* Specifications for other protocols implemented by USB peripheral
functions. Some are vendor-specific; others are vendor-neutral
but just standardized outside of the www.usb.org team.
Here is a list of what each subdirectory here is, and what is contained in
them.
core/ - This is for the core USB host code, including the
usbfs files and the hub class driver ("khubd").
host/ - This is for USB host controller drivers. This
includes UHCI, OHCI, EHCI, and others that might
be used with more specialized "embedded" systems.
gadget/ - This is for USB peripheral controller drivers and
the various gadget drivers which talk to them.
Individual USB driver directories. A new driver should be added to the
first subdirectory in the list below that it fits into.
image/ - This is for still image drivers, like scanners or
digital cameras.
../input/ - This is for any driver that uses the input subsystem,
like keyboard, mice, touchscreens, tablets, etc.
../media/ - This is for multimedia drivers, like video cameras,
radios, and any other drivers that talk to the v4l
subsystem.
../net/ - This is for network drivers.
serial/ - This is for USB to serial drivers.
storage/ - This is for USB mass-storage drivers.
class/ - This is for all USB device drivers that do not fit
into any of the above categories, and work for a range
of USB Class specified devices.
misc/ - This is for all USB device drivers that do not fit
into any of the above categories.