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path: root/drivers/usb/host/xhci-ring.c
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2009-09-23USB: xhci: Support interrupt transfers.Sarah Sharp
Interrupt transfers are submitted to the xHCI hardware using the same TRB type as bulk transfers. Re-use the bulk transfer enqueueing code to enqueue interrupt transfers. Interrupt transfers are a bit different than bulk transfers. When the interrupt endpoint is to be serviced, the xHC will consume (at most) one TD. A TD (comprised of sg list entries) can take several service intervals to transmit. The important thing for device drivers to note is that if they use the scatter gather interface to submit interrupt requests, they will not get data sent from two different scatter gather lists in the same service interval. For now, the xHCI driver will use the service interval from the endpoint's descriptor (bInterval). Drivers will need a hook to poll at a more frequent interval. Set urb->interval to the interval that the xHCI hardware will use. Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com> Cc: stable <stable@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2009-09-23USB: xhci: Set -EREMOTEIO when xHC gives bad transfer length.Sarah Sharp
The xHCI hardware reports the number of bytes untransferred for a given transfer buffer. If the hardware reports a bytes untransferred value greater than the submitted buffer size, we want to play it safe and say no data was transferred. If the driver considers a short packet to be an error, remember to set -EREMOTEIO. Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com> Cc: stable <stable@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2009-09-23USB: xhci: Check URB_SHORT_NOT_OK before setting short packet status.Sarah Sharp
Make sure that the driver that submitted the URB considers a short packet an error before setting -EREMOTEIO during a short control transfer. Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com> Cc: stable <stable@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2009-09-23USB: xhci: Check URB's actual transfer buffer size.Sarah Sharp
Make sure that the amount of data the xHC says was transmitted is less than or equal to the size of the requested transfer buffer. Before, if the host controller erroneously reported that the number of bytes untransferred was bigger than the buffer in the URB, urb->actual_length could be set to a very large size. Make sure urb->actual_length <= urb->transfer_buffer_length. Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com> Cc: stable <stable@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2009-09-23USB: xhci: Don't touch xhci_td after it's freed.Sarah Sharp
On a successful transfer, urb->td is freed before the URB is ready to be given back to the driver. Don't touch urb->td after it's freed. This bug would have only shown up when xHCI debugging was turned on, and the freed memory was quickly reused for something else. Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com> Cc: stable <stable@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2009-09-23USB: xhci: Handle babbling endpoints correctly.Sarah Sharp
The 0.95 xHCI spec says that non-control endpoints will be halted if a babble is detected on a transfer. The 0.96 xHCI spec says all types of endpoints will be halted when a babble is detected. Some hardware that claims to be 0.95 compliant halts the control endpoint anyway. When a babble is detected on a control endpoint, check the hardware's output endpoint context to see if the endpoint is marked as halted. If the control endpoint is halted, a reset endpoint command must be issued and the transfer ring dequeue pointer needs to be moved past the stopped transfer. Basically, we treat it as if the control endpoint had stalled. Handle bulk babbling endpoints as if we got a completion event with a stall completion code. Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com> Cc: stable <stable@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2009-09-23USB: xhci: Make TRB completion code comparison readable.Sarah Sharp
Use trb_comp_code instead of getting the completion code from the transfer event every time. Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com> Cc: stable <stable@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2009-09-23USB: xhci: Add quirk for Fresco Logic xHCI hardware.Sarah Sharp
This Fresco Logic xHCI host controller chip revision puts bad data into the output endpoint context after a Reset Endpoint command. It needs a Configure Endpoint command (instead of a Set TR Dequeue Pointer command) after the reset endpoint command. Set up the input context before issuing the Reset Endpoint command so we don't copy bad data from the output endpoint context. The HW also can't handle two commands queued at once, so submit the TRB for the Configure Endpoint command in the event handler for the Reset Endpoint command. Devices that stall on control endpoints before a configuration is selected will not work under this Fresco Logic xHCI host controller revision. This patch is for prototype hardware that will be given to other companies for evaluation purposes only, and should not reach consumer hands. Fresco Logic's next chip rev should have this bug fixed. Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com> Cc: stable <stable@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2009-09-23USB: xhci: Handle stalled control endpoints.Sarah Sharp
When a control endpoint stalls, the next control transfer will clear the stall. The USB core doesn't call down to the host controller driver's endpoint_reset() method when control endpoints stall, so the xHCI driver has to do all its stall handling for internal state in its interrupt handler. When the host stalls on a control endpoint, it may stop on the data phase or status phase of the control transfer. Like other stalled endpoints, the xHCI driver needs to queue a Reset Endpoint command and move the hardware's control endpoint ring dequeue pointer past the failed control transfer (with a Set TR Dequeue Pointer or a Configure Endpoint command). Since the USB core doesn't call usb_hcd_reset_endpoint() for control endpoints, we need to do this in interrupt context when we get notified of the stalled transfer. URBs may be queued to the hardware before these two commands complete. The endpoint queue will be restarted once both commands complete. Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com> Cc: stable <stable@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2009-09-23USB: xhci: Support full speed devices.Sarah Sharp
Full speed devices have varying max packet sizes (8, 16, 32, or 64) for endpoint 0. The xHCI hardware needs to know the real max packet size that the USB core discovers after it fetches the first 8 bytes of the device descriptor. In order to fix this without adding a new hook to host controller drivers, the xHCI driver looks for an updated max packet size for control endpoints. If it finds an updated size, it issues an evaluate context command and waits for that command to finish. This should only happen in the initialization and device descriptor fetching steps in the khubd thread, so blocking should be fine. Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com> Cc: stable <stable@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2009-09-23USB: xhci: Configure endpoint code refactoring.Sarah Sharp
Refactor out the code issue, wait for, and parse the event completion code for a configure endpoint command. Modify it to support the evaluate context command, which has a very similar submission process. Add functions to copy parts of the output context into the input context (which will be used in the evaluate context command). Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com> Cc: stable <stable@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2009-09-23USB: xhci: Work around for chain bit in link TRBs.Sarah Sharp
Different sections of the xHCI 0.95 specification had opposing requirements for the chain bit in a link transaction request buffer (TRB). The chain bit is used to designate that adjacent TRBs are all part of the same scatter gather list that should be sent to the device. Link TRBs can be in the middle, or at the beginning or end of these chained TRBs. Sections 4.11.5.1 and 6.4.4.1 both stated the link TRB "shall have the chain bit set to 1", meaning it is always chained to the next TRB. However, section 4.6.9 on the stop endpoint command has specific cases for what the hardware must do for a link TRB with the chain bit set to 0. The 0.96 specification errata later cleared up this issue by fixing the 4.11.5.1 and 6.4.4.1 sections to state that a link TRB can have the chain bit set to 1 or 0. The problem is that the xHCI cancellation code depends on the chain bit of the link TRB being cleared when it's at the end of a TD, and some 0.95 xHCI hardware simply stops processing the ring when it encounters a link TRB with the chain bit cleared. Allow users who are testing 0.95 xHCI prototypes to set a module parameter (link_quirk) to turn on this link TRB work around. Cancellation may not work if the ring is stopped exactly on a link TRB with chain bit set, but cancellation should be a relatively uncommon case. Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com> Cc: stable <stable@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2009-07-28USB: xhci: Stall handling bug fixes.Sarah Sharp
Correct the xHCI code to handle stalls on USB endpoints. We need to move the endpoint ring's dequeue pointer past the stalled transfer, or the HW will try to restart the transfer the next time the doorbell is rung. Don't attempt to clear a halt on an endpoint if we haven't seen a stalled transfer for it. The USB core will attempt to clear a halt on all endpoints when it selects a new configuration. Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2009-07-28USB: xhci: Support for 64-byte contextsJohn Youn
Adds support for controllers that use 64-byte contexts. The following context data structures are affected by this: Device, Input, Input Control, Endpoint, and Slot. To accommodate the use of either 32 or 64-byte contexts, a Device or Input context can only be accessed through functions which look-up and return pointers to their contained contexts. Signed-off-by: John Youn <johnyoun@synopsys.com> Acked-by: Sarah Sharp <sarah.a.sharp@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2009-07-28USB: xhci: Handle babble errors on transfers.Sarah Sharp
Pass back a babble error when this error code is seen in the transfer event TRB. Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2009-07-28USB: xhci: Make debugging more verbose.Sarah Sharp
Add more debugging to the irq handler, slot context initialization, ring operations, URB cancellation, and MMIO writes. Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2009-07-28USB: xhci: Correct Event Handler Busy flag usage.Sarah Sharp
The Event Handler Busy bit in the event ring dequeue pointer is write 1 to clear. Fix the interrupt service routine to clear that bit after the event handler has run. xhci_set_hc_event_deq() is designed to update the event ring dequeue pointer without changing any of the four reserved bits in the lower nibble. The event handler busy (EHB) bit is write one to clear, so the new value must always contain a zero in that bit in order to preserve the EHB value. Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2009-07-28USB: xhci: Handle short control packets correctly.Sarah Sharp
When there is a short packet on a control transfer, the xHCI host controller hardware will generate two events. The first event will be for the data stage TD with a completion code for a short packet. The second event will be for the status stage with a successful completion code. Before this patch, the xHCI driver would giveback the short control URB when it received the event for the data stage TD. Then it would become confused when it saw a status stage event for the endpoint for an URB it had already finished processing. Change the xHCI host controller driver to wait for the status stage event when it receives a short transfer completion code for a data stage TD. Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2009-07-28USB: xhci: Represent 64-bit addresses with one u64.Sarah Sharp
There are several xHCI data structures that use two 32-bit fields to represent a 64-bit address. Since some architectures don't support 64-bit PCI writes, the fields need to be written in two 32-bit writes. The xHCI specification says that if a platform is incapable of generating 64-bit writes, software must write the low 32-bits first, then the high 32-bits. Hardware that supports 64-bit addressing will wait for the high 32-bit write before reading the revised value, and hardware that only supports 32-bit writes will ignore the high 32-bit write. Previous xHCI code represented 64-bit addresses with two u32 values. This lead to buggy code that would write the 32-bits in the wrong order, or forget to write the upper 32-bits. Change the two u32s to one u64 and create a function call to write all 64-bit addresses in the proper order. This new function could be modified in the future if all platforms support 64-bit writes. Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2009-07-28USB: xhci: Deal with stalled endpoints.Sarah Sharp
When an endpoint on a device under an xHCI host controller stalls, the host controller driver must let the hardware know that the USB core has successfully cleared the halt condition. The HCD submits a Reset Endpoint Command, which will clear the toggle bit for USB 2.0 devices, and set the sequence number to zero for USB 3.0 devices. The xHCI urb_enqueue will accept new URBs while the endpoint is halted, and will queue them to the hardware rings. However, the endpoint doorbell will not be rung until the Reset Endpoint Command completes. Don't queue a reset endpoint command for root hubs. khubd clears halt conditions on the roothub during the initialization process, but the roothub isn't a real device, so the xHCI host controller doesn't need to know about the cleared halt. Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2009-07-28USB: xhci: Set TD size in transfer TRB.Sarah Sharp
The 0.95 xHCI specification requires software to set the "TD size" field in each transaction request block (TRB). This field gives the host controller an indication of how much data is remaining in the TD (including the buffer in the current TRB). Set this field in bulk TRBs and data stage TRBs for control transfers. Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2009-06-15usb; xhci: Fix TRB offset calculations.Sarah Sharp
Greg KH introduced a bug into xhci_trb_virt_to_dma() when he changed the type of offset to dma_addr_t from unsigned int and dropped the casts to unsigned int around the virtual address pointer subtraction. trb and seg->trbs are both valid pointers to virtual addresses, so the compiler will mod the subtraction by the size of union trb (16 bytes). segment_offset is an unsigned long, which is guaranteed to be at least as big as a void *. Drop the void * casts in the first if statement because trb and seg->trbs are both pointers of the same type (pointers to union trb). Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2009-06-15USB: xhci: Avoid compiler reordering in Link TRB giveback.Sarah Sharp
Force the compiler to write the cycle bit of the Link TRB last. This ensures that the hardware doesn't think it owns the Link TRB before we set the chain bit. Reported by Oliver in this thread: http://marc.info/?l=linux-usb&m=124091532410219&w=2 Reported-by: Oliver Neukum <oliver@neukum.org> Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2009-06-15USB: xhci: Avoid global namespace pollution.Sarah Sharp
Make all globally visible functions start with xhci_ and mark functions as static if they're only called within the same C file. Fix some long lines while we're at it. Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2009-06-15USB: xhci: Fix Link TRB handoff bit twiddling.Sarah Sharp
Make sure to preserve all bits *except* the TRB_CHAIN bit when giving a Link TRB to the hardware. We need to save things like TRB type and the toggle bit in the control dword. Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2009-06-15USB: xhci: fix lots of compiler warnings.Greg Kroah-Hartman
Turns out someone never built this code on a 64bit platform. Someone owes me a beer... Reported-by: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Sarah Sharp <sarah.a.sharp@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2009-06-15USB: xhci: use xhci_handle_event instead of handle_eventStephen Rothwell
The former is way to generic for a global symbol. Fixes this build error: drivers/usb/built-in.o: In function `.handle_event': (.text+0x67dd0): multiple definition of `.handle_event' drivers/pcmcia/built-in.o:(.text+0xcfcc): first defined here drivers/usb/built-in.o: In function `handle_event': (.opd+0x5bc8): multiple definition of `handle_event' drivers/pcmcia/built-in.o:(.opd+0xed0): first defined here Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Sarah Sharp <sarah.a.sharp@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2009-06-15USB: xhci: URB cancellation support.Sarah Sharp
Add URB cancellation support to the xHCI host controller driver. This currently supports cancellation for endpoints that do not have streams enabled. An URB is represented by a number of Transaction Request Buffers (TRBs), that are chained together to make one (or more) Transaction Descriptors (TDs) on an endpoint ring. The ring is comprised of contiguous segments, linked together with Link TRBs (which may or may not be chained into a TD). To cancel an URB, we must stop the endpoint ring, make the hardware skip over the TDs in the URB (either by turning them into No-op TDs, or by moving the hardware's ring dequeue pointer past the last TRB in the last TD), and then restart the ring. There are times when we must drop the xHCI lock during this process, like when we need to complete cancelled URBs. We must ensure that additional URBs can be marked as cancelled, and that new URBs can be enqueued (since the URB completion handlers can do either). The new endpoint ring variables cancels_pending and state (which can only be modified while holding the xHCI lock) ensure that future cancellation and enqueueing do not interrupt any pending cancellation code. To facilitate cancellation, we must keep track of the starting ring segment, first TRB, and last TRB for each URB. We also need to keep track of the list of TDs that have been marked as cancelled, separate from the list of TDs that are queued for this endpoint. The new variables and cancellation list are stored in the xhci_td structure. Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2009-06-15USB: xhci: Scatter gather list support for bulk transfers.Sarah Sharp
Add support for bulk URBs that pass scatter gather lists to xHCI. This allows xHCI to more efficiently enqueue these transfers, and allows the host controller to take advantage of USB 3.0 "bursts" for bulk endpoints. Use requested length to calculate the number of TRBs needed for a scatter gather list transfer, instead of using the number of sglist entries. The application can pass down a scatter gather list that is bigger than it needs for the requested transfer. Scatter gather entries can cross 64KB boundaries, so be careful to setup TRBs such that no buffer crosses a 64KB boundary. Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2009-06-15USB: xhci: Bulk transfer supportSarah Sharp
Allow device drivers to submit URBs to bulk endpoints on devices under an xHCI host controller. Share code between the control and bulk enqueueing functions when it makes sense. To get the best performance out of bulk transfers, SuperSpeed devices must have the bMaxBurst size copied from their endpoint companion controller into the xHCI device context. This allows the host controller to "burst" up to 16 packets before it has to wait for the device to acknowledge the first packet. The buffers in Transfer Request Blocks (TRBs) can cross page boundaries, but they cannot cross 64KB boundaries. The buffer must be broken into multiple TRBs if a 64KB boundary is crossed. The sum of buffer lengths in all the TRBs in a Transfer Descriptor (TD) cannot exceed 64MB. To work around this, the enqueueing code must enqueue multiple TDs. The transfer event handler may incorrectly give back the URB in this case, if it gets a transfer event that points somewhere in the first TD. FIXME later. Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2009-06-15USB: xhci: Bandwidth allocation supportSarah Sharp
Since the xHCI host controller hardware (xHC) has an internal schedule, it needs a better representation of what devices are consuming bandwidth on the bus. Each device is represented by a device context, with data about the device, endpoints, and pointers to each endpoint ring. We need to update the endpoint information for a device context before a new configuration or alternate interface setting is selected. We setup an input device context with modified endpoint information and newly allocated endpoint rings, and then submit a Configure Endpoint Command to the hardware. The host controller can reject the new configuration if it exceeds the bus bandwidth, or the host controller doesn't have enough internal resources for the configuration. If the command fails, we still have the older device context with the previous configuration. If the command succeeds, we free the old endpoint rings. The root hub isn't a real device, so always say yes to any bandwidth changes for it. The USB core will enable, disable, and then enable endpoint 0 several times during the initialization sequence. The device will always have an endpoint ring for endpoint 0 and bandwidth allocated for that, unless the device is disconnected or gets a SetAddress 0 request. So we don't pay attention for when xhci_check_bandwidth() is called for a re-add of endpoint 0. Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2009-06-15USB: xhci: Control transfer support.Sarah Sharp
Allow device drivers to enqueue URBs to control endpoints on devices under an xHCI host controller. Each control transfer is represented by a series of Transfer Descriptors (TDs) written to an endpoint ring. There is one TD for the Setup phase, (optionally) one TD for the Data phase, and one TD for the Status phase. Enqueue these TDs onto the endpoint ring that represents the control endpoint. The host controller hardware will return an event on the event ring that points to the (DMA) address of one of the TDs on the endpoint ring. If the transfer was successful, the transfer event TRB will have a completion code of success, and it will point to the Status phase TD. Anything else is considered an error. This should work for control endpoints besides the default endpoint, but that hasn't been tested. Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2009-06-15USB: xhci: Allocate and address USB devicesSarah Sharp
xHCI needs to get a "Slot ID" from the host controller and allocate other data structures for every USB device. Make usb_alloc_dev() and usb_release_dev() allocate and free these device structures. After setting up the xHC device structures, usb_alloc_dev() must wait for the hardware to respond to an Enable Slot command. usb_alloc_dev() fires off a Disable Slot command and does not wait for it to complete. When the USB core wants to choose an address for the device, the xHCI driver must issue a Set Address command and wait for an event for that command. Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2009-06-15USB: xhci: Root hub support.Sarah Sharp
Add functionality for getting port status and hub descriptor for xHCI root hubs. This is WIP because the USB 3.0 hub descriptor is different from the USB 2.0 hub descriptor. For now, we lie about the root hub descriptor because the changes won't effect how the core talks to the root hub. Later we will need to add the USB 3.0 hub descriptor for real hubs, and this code might change. Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2009-06-15USB: xhci: No-op command queueing and irq handler.Sarah Sharp
xHCI host controllers can optionally implement a no-op test. This simple test ensures the OS has correctly setup all basic data structures and can correctly respond to interrupts from the host controller hardware. There are two rings exercised by the no-op test: the command ring, and the event ring. The host controller driver writes a no-op command TRB to the command ring, and rings the doorbell for the command ring (the first entry in the doorbell array). The hardware receives this event, places a command completion event on the event ring, and fires an interrupt. The host controller driver sees the interrupt, and checks the event ring for TRBs it can process, and sees the command completion event. (See the rules in xhci-ring.c for who "owns" a TRB. This is a simplified set of rules, and may not contain all the details that are in the xHCI 0.95 spec.) A timer fires every 60 seconds to debug the state of the hardware and command and event rings. This timer only runs if CONFIG_USB_XHCI_HCD_DEBUGGING is 'y'. Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>