kernel/drivers/usb/core/hub.h, branch linux-4.3.y

usb: hub: convert khubd into workqueue

2014-09-24T05:33:19Z

There is no need to have separate kthread for handling USB hub events. It is more elegant to use the workqueue framework. The workqueue is allocated as freezable because the original thread was freezable as well. Also it is allocated as ordered because the code is not ready for parallel processing of hub events, see choose_devnum(). struct usb_hub is passed via the work item. Therefore we do not need hub_event_list. Also hub_thread() is not longer needed. It would call only hub_event(). The rest of the code did manipulate the kthread and it is handled by the workqueue framework now. kick_khubd is renamed to kick_hub_wq() to make the function clear. And the protection against races is done another way, see below. hub_event_lock has been removed. It cannot longer be used to protect struct usb_hub between hub_event() and hub_disconnect(). Instead we need to get hub->kref already in kick_hub_wq(). The lock is not really needed for the other scenarios as well. queue_work() returns whether it succeeded. We could revert the needed operations accordingly. This is enough to avoid duplicity and inconsistencies. Yes, the removed lock causes that there is not longer such a strong synchronization between scheduling the work and manipulating hub->disconnected. But kick_hub_wq() must never be called together with hub_disconnect() otherwise even the original code would have failed. Any callers are responsible for this. Therefore the only problem is that hub_disconnect() could be called in parallel with hub_event(). But this was possible even in the past. struct usb_hub is still guarded by hub->kref and released in hub_events() when needed. Note that the source file is still full of the obsolete "khubd" strings. Let's remove them in a follow up patch. This patch already is complex enough. Thanks a lot Alan Stern for code review, many useful tips and guidance. Also thanks to Tejun Heo for hints how to allocate the workqueue. Signed-off-by: Petr Mladek Acked-by: Alan Stern Signed-off-by: Greg Kroah-Hartman

usb: force warm reset to break link re-connect livelock

2014-07-09T22:43:12Z

Resuming a powered down port sometimes results in the port state being stuck in the training sequence. hub 3-0:1.0: debounce: port 1: total 2000ms stable 0ms status 0x2e0 port1: can't get reconnection after setting port power on, status -110 hub 3-0:1.0: port 1 status 0000.02e0 after resume, -19 usb 3-1: can't resume, status -19 hub 3-0:1.0: logical disconnect on port 1 In the case above we wait for the port re-connect timeout of 2 seconds and observe that the port status is USB_SS_PORT_LS_POLLING (although it is likely toggling between this state and USB_SS_PORT_LS_RX_DETECT). This is indicative of a case where the device is failing to progress the link training state machine. It is resolved by issuing a warm reset to get the hub and device link state machines back in sync. hub 3-0:1.0: debounce: port 1: total 2000ms stable 0ms status 0x2e0 usb usb3: port1 usb_port_runtime_resume requires warm reset hub 3-0:1.0: port 1 not warm reset yet, waiting 50ms usb 3-1: reset SuperSpeed USB device number 2 using xhci_hcd After a reconnect timeout when we expect the device to be present, force a warm reset of the device. Note that we can not simply look at the link status to determine if a warm reset is required as any of the training states USB_SS_PORT_LS_POLLING, USB_SS_PORT_LS_RX_DETECT, or USB_SS_PORT_LS_COMP_MOD are valid states that do not indicate the need for warm reset by themselves. Cc: Alan Stern Cc: Kukjin Kim Cc: Vincent Palatin Cc: Lan Tianyu Cc: Ksenia Ragiadakou Cc: Vivek Gautam Cc: Douglas Anderson Cc: Felipe Balbi Cc: Sunil Joshi Cc: Hans de Goede Acked-by: Julius Werner Signed-off-by: Dan Williams Acked-by: Alan Stern Signed-off-by: Greg Kroah-Hartman

usb: fix hub-port pm_runtime_enable() vs runtime pm transitions

2014-06-18T00:04:39Z

Commit 9262c19d14c4 "usb: disable port power control if not supported in wHubCharacteristics" gated enabling runtime pm for usb_port devices on whether the parent hub supports power control, which causes a regression. The port must still be allowed to carry out runtime pm callbacks and receive a -EAGAIN or -EBUSY result. Otherwise the usb_port device will transition to the pm error state and trigger the same for the child usb_device. Prior to the offending commit usb_hub_create_port_device() arranged for runtime pm to be disabled is dev_pm_qos_expose_flags() failed. Instead, force the default state of PM_QOS_FLAG_NO_POWER_OFF flag to be set prior to enabling runtime pm. If that policy can not be set then fail registration. Report: http://marc.info/?l=linux-usb&m=140290586301336&w=2 Fixes: 9262c19d14c4 ("usb: disable port power control if not supported in wHubCharacteristics") Reported-by: Bjørn Mork Reported-by: Alan Stern Signed-off-by: Dan Williams Signed-off-by: Greg Kroah-Hartman

usb: introduce port status lock

2014-05-27T23:51:50Z

In general we do not want khubd to act on port status changes that are the result of in progress resets or USB runtime PM operations. Specifically port power control testing has been able to trigger an unintended disconnect in hub_port_connect_change(), paraphrasing: if ((portstatus & USB_PORT_STAT_CONNECTION) && udev && udev->state != USB_STATE_NOTATTACHED) { if (portstatus & USB_PORT_STAT_ENABLE) { /* Nothing to do */ } else if (udev->state == USB_STATE_SUSPENDED && udev->persist_enabled) { ... } else { /* Don't resuscitate */; } } ...by falling to the "Don't resuscitate" path or missing USB_PORT_STAT_CONNECTION because usb_port_resume() was in the middle of modifying the port status. So, we want a new lock to hold off khubd for a given port while the child device is being suspended, resumed, or reset. The lock ordering rules are now usb_lock_device() => usb_lock_port(). This is mandated by the device core which may hold the device_lock on the usb_device before invoking usb_port_{suspend|resume} which in turn take the status_lock on the usb_port. We attempt to hold the status_lock for the duration of a port_event() run, and drop/re-acquire it when needing to take the device_lock. The lock is also dropped/re-acquired during hub_port_reconnect(). This patch also deletes hub->busy_bits as all use cases are now covered by port PM runtime synchronization or the port->status_lock and it pushes down usb_device_lock() into usb_remote_wakeup(). Acked-by: Alan Stern Signed-off-by: Dan Williams Signed-off-by: Greg Kroah-Hartman

usb: block suspension of superspeed port while hispeed peer is active

2014-05-27T23:38:53Z

ClearPortFeature(PORT_POWER) on a usb3 port places the port in either a DSPORT.Powered-off-detect / DSPORT.Powered-off-reset loop, or the DSPORT.Powered-off state. There is no way to ensure that RX terminations will persist in this state, so it is possible a device will degrade to its usb2 connection. Prevent this by blocking power-off of a usb3 port while its usb2 peer is active, and powering on a usb3 port before its usb2 peer. By default the latency between peer power-on events is 0. In order for the device to not see usb2 active while usb3 is still powering up inject the hub recommended power_on_good delay. In support of satisfying the power_on_good delay outside of hub_power_on() refactor the places where the delay is consumed to call a new hub_power_on_good_delay() helper. Finally, because this introduces several new checks for whether a port is_superspeed, cache that disctinction at port creation so that we don't need to keep looking up the parent hub device. Acked-by: Alan Stern [alan]: add a 'superspeed' flag to the port Signed-off-by: Dan Williams Signed-off-by: Greg Kroah-Hartman

usb: make usb_port flags atomic, rename did_runtime_put to child_usage

2014-05-27T23:38:53Z

We want to manipulate ->did_runtime_put in usb_port_runtime_resume(), but we don't want that to collide with other updates. Move usb_port flags to new port-bitmap fields in usb_hub. "did_runtime_put" is renamed "child_usage_bits" to reflect that it is strictly standing in for the fact that usb_devices are not the device_model children of their parent port. Signed-off-by: Dan Williams Acked-by: Alan Stern Signed-off-by: Greg Kroah-Hartman

usb: find internal hub tier mismatch via acpi

2014-05-27T23:38:52Z

ACPI identifies peer ports by setting their 'group_token' and 'group_position' _PLD data to the same value. If a platform has tier mismatch [1] , ACPI can override the default (USB3 defined) peer port association for internal hubs. External hubs follow the default peer association scheme. Location data is cached as an opaque cookie in usb_port_location data. Note that we only consider the group_token and group_position attributes from the _PLD data as ACPI specifies that group_token is a unique identifier. When we find port location data for a port then we assume that the firmware will also describe its peer port. This allows the implementation to only ever set the peer once. This leads to a question about what happens when a pm runtime event occurs while the peer associations are still resolving. Since we only ever set the peer information once, a USB3 port needs to be prevented from suspending while its ->peer pointer is NULL (implemented in a subsequent patch). There is always the possibility that firmware mis-identifies the ports, but there is not much the kernel can do in that case. [1]: xhci 1.1 appendix D figure 131 [2]: acpi 5 section 6.1.8 [alan]: don't do default peering when acpi data present Suggested-by: Alan Stern Acked-by: Alan Stern Signed-off-by: Dan Williams Signed-off-by: Greg Kroah-Hartman

usb: assign default peer ports for root hubs

2014-05-27T23:38:52Z

Assume that the peer of a superspeed port is the port with the same id on the shared_hcd root hub. This identification scheme is required of external hubs by the USB3 spec [1]. However, for root hubs, tier mismatch may be in effect [2]. Tier mismatch can only be enumerated via platform firmware. For now, simply perform the nominal association. A new lock 'usb_port_peer_mutex' is introduced to synchronize port device add/remove with peer lookups. It protects peering against changes to hcd->shared_hcd, hcd->self.root_hub, hdev->maxchild, and port_dev->child pointers. [1]: usb 3.1 section 10.3.3 [2]: xhci 1.1 appendix D Cc: Alan Stern [alan: usb_port_peer_mutex locking scheme] Acked-by: Alan Stern Signed-off-by: Dan Williams Signed-off-by: Greg Kroah-Hartman

usb: disable port power control if not supported in wHubCharacteristics

2014-05-27T23:35:09Z

A hub indicates whether it supports per-port power control via the wHubCharacteristics field in its descriptor. If it is not supported a hub will still emulate ClearPortPower(PORT_POWER) requests by stopping the link state machine. However, since this does not save power do not bother suspending. This also consolidates support checks into a hub_is_port_power_switchable() helper. Acked-by: Alan Stern Signed-off-by: Dan Williams Signed-off-by: Greg Kroah-Hartman

USB: mutual exclusion for resetting a hub and power-managing a port

2014-05-27T23:28:03Z

The USB core doesn't properly handle mutual exclusion between resetting a hub and changing the power states of the hub's ports. We need to avoid sending port-power requests to the hub while it is being reset, because such requests cannot succeed. This patch fixes the problem by keeping track of when a reset is in progress. At such times, attempts to suspend (power-off) a port will fail immediately with -EBUSY, and calls to usb_port_runtime_resume() will update the power_is_on flag and return immediately. When the reset is complete, hub_activate() will automatically restore each port to the proper power state. Signed-off-by: Alan Stern Signed-off-by: Dan Williams Signed-off-by: Greg Kroah-Hartman