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USB: EHCI: use hrtimer for interrupt QH unlink 

This patch (as1577) adds hrtimer support for unlinking interrupt QHs
in ehci-hcd.  The current code relies on a fixed delay of either 2 or
55 us, which is not always adequate and in any case is totally bogus.
Thanks to internal caching, the EHCI hardware may continue to access
an interrupt QH for more than a millisecond after it has been unlinked.

In fact, the EHCI spec doesn't say how long to wait before using an
unlinked interrupt QH.  The patch sets the delay to 9 microframes
minimum, which ought to be adequate.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Alan Stern 2012-07-11 11:22:26 -04:00 committed by Greg Kroah-Hartman
parent 314466101c
commit df2022553d
5 changed files with 96 additions and 30 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
drivers/usb/host/ehci-hcd.c
View File

@ -309,6 +309,8 @@ static void ehci_quiesce (struct ehci_hcd *ehci)
static void end_unlink_async(struct ehci_hcd *ehci);
static void ehci_work(struct ehci_hcd *ehci);
static void start_unlink_intr(struct ehci_hcd *ehci, struct ehci_qh *qh);
static void end_unlink_intr(struct ehci_hcd *ehci, struct ehci_qh *qh);
#include "ehci-timer.c"
#include "ehci-hub.c"
@ -1034,7 +1036,7 @@ static int ehci_urb_dequeue(struct usb_hcd *hcd, struct urb *urb, int status)
switch (qh->qh_state) {
case QH_STATE_LINKED:
case QH_STATE_COMPLETING:
intr_deschedule (ehci, qh);
start_unlink_intr(ehci, qh);
break;
case QH_STATE_IDLE:
qh_completions (ehci, qh);
@ -1164,7 +1166,7 @@ ehci_endpoint_reset(struct usb_hcd *hcd, struct usb_host_endpoint *ep)
if (eptype == USB_ENDPOINT_XFER_BULK)
unlink_async(ehci, qh);
else
intr_deschedule(ehci, qh);
start_unlink_intr(ehci, qh);
}
}
spin_unlock_irqrestore(&ehci->lock, flags);

1
drivers/usb/host/ehci-hub.c
View File

@ -302,6 +302,7 @@ static int ehci_bus_suspend (struct usb_hcd *hcd)
if (ehci->async_unlink)
end_unlink_async(ehci);
ehci_handle_intr_unlinks(ehci);
/* allow remote wakeup */
mask = INTR_MASK;

75
drivers/usb/host/ehci-sched.c
View File

@ -578,12 +578,20 @@ static void qh_unlink_periodic(struct ehci_hcd *ehci, struct ehci_qh *qh)
unsigned i;
unsigned period;
// FIXME:
// IF this isn't high speed
// and this qh is active in the current uframe
// (and overlay token SplitXstate is false?)
// THEN
// qh->hw_info1 |= cpu_to_hc32(1 << 7 /* "ignore" */);
/*
* If qh is for a low/full-speed device, simply unlinking it
* could interfere with an ongoing split transaction. To unlink
* it safely would require setting the QH_INACTIVATE bit and
* waiting at least one frame, as described in EHCI 4.12.2.5.
*
* We won't bother with any of this. Instead, we assume that the
* only reason for unlinking an interrupt QH while the current URB
* is still active is to dequeue all the URBs (flush the whole
* endpoint queue).
*
* If rebalancing the periodic schedule is ever implemented, this
* approach will no longer be valid.
*/
/* high bandwidth, or otherwise part of every microframe */
if ((period = qh->period) == 0)
@ -608,12 +616,8 @@ static void qh_unlink_periodic(struct ehci_hcd *ehci, struct ehci_qh *qh)
qh->qh_next.ptr = NULL;
}
static void intr_deschedule (struct ehci_hcd *ehci, struct ehci_qh *qh)
static void start_unlink_intr(struct ehci_hcd *ehci, struct ehci_qh *qh)
{
unsigned wait;
struct ehci_qh_hw *hw = qh->hw;
int rc;
/* If the QH isn't linked then there's nothing we can do
* unless we were called during a giveback, in which case
* qh_completions() has to deal with it.
@ -626,28 +630,45 @@ static void intr_deschedule (struct ehci_hcd *ehci, struct ehci_qh *qh)
qh_unlink_periodic (ehci, qh);
/* simple/paranoid: always delay, expecting the HC needs to read
* qh->hw_next or finish a writeback after SPLIT/CSPLIT ... and
* expect khubd to clean up after any CSPLITs we won't issue.
* active high speed queues may need bigger delays...
*/
if (list_empty (&qh->qtd_list)
|| (cpu_to_hc32(ehci, QH_CMASK)
& hw->hw_info2) != 0)
wait = 2;
else
wait = 55; /* worst case: 3 * 1024 */
/* Make sure the unlinks are visible before starting the timer */
wmb();
/*
* The EHCI spec doesn't say how long it takes the controller to
* stop accessing an unlinked interrupt QH. The timer delay is
* 9 uframes; presumably that will be long enough.
*/
qh->unlink_cycle = ehci->intr_unlink_cycle;
/* New entries go at the end of the intr_unlink list */
if (ehci->intr_unlink)
ehci->intr_unlink_last->unlink_next = qh;
else
ehci->intr_unlink = qh;
ehci->intr_unlink_last = qh;
if (ehci->intr_unlinking)
; /* Avoid recursive calls */
else if (ehci->rh_state < EHCI_RH_RUNNING)
ehci_handle_intr_unlinks(ehci);
else if (ehci->intr_unlink == qh) {
ehci_enable_event(ehci, EHCI_HRTIMER_UNLINK_INTR, true);
++ehci->intr_unlink_cycle;
}
}
static void end_unlink_intr(struct ehci_hcd *ehci, struct ehci_qh *qh)
{
struct ehci_qh_hw *hw = qh->hw;
int rc;
udelay (wait);
qh->qh_state = QH_STATE_IDLE;
hw->hw_next = EHCI_LIST_END(ehci);
wmb ();
qh_completions(ehci, qh);
/* reschedule QH iff another request is queued */
if (!list_empty(&qh->qtd_list) &&
ehci->rh_state == EHCI_RH_RUNNING) {
if (!list_empty(&qh->qtd_list) && ehci->rh_state == EHCI_RH_RUNNING) {
rc = qh_schedule(ehci, qh);
/* An error here likely indicates handshake failure
@ -2302,7 +2323,7 @@ restart:
temp.qh->stamp = ehci->periodic_stamp;
if (unlikely(list_empty(&temp.qh->qtd_list) ||
temp.qh->needs_rescan))
intr_deschedule(ehci, temp.qh);
start_unlink_intr(ehci, temp.qh);
}
break;
case Q_TYPE_FSTN:

34
drivers/usb/host/ehci-timer.c
View File

@ -69,6 +69,7 @@ static void ehci_clear_command_bit(struct ehci_hcd *ehci, u32 bit)
static unsigned event_delays_ns[] = {
1 * NSEC_PER_MSEC, /* EHCI_HRTIMER_POLL_ASS */
1 * NSEC_PER_MSEC, /* EHCI_HRTIMER_POLL_PSS */
1125 * NSEC_PER_USEC, /* EHCI_HRTIMER_UNLINK_INTR */
10 * NSEC_PER_MSEC, /* EHCI_HRTIMER_DISABLE_PERIODIC */
15 * NSEC_PER_MSEC, /* EHCI_HRTIMER_DISABLE_ASYNC */
};
@ -192,6 +193,38 @@ static void ehci_disable_PSE(struct ehci_hcd *ehci)
}
/* Handle unlinked interrupt QHs once they are gone from the hardware */
static void ehci_handle_intr_unlinks(struct ehci_hcd *ehci)
{
bool stopped = (ehci->rh_state < EHCI_RH_RUNNING);
/*
* Process all the QHs on the intr_unlink list that were added
* before the current unlink cycle began. The list is in
* temporal order, so stop when we reach the first entry in the
* current cycle. But if the root hub isn't running then
* process all the QHs on the list.
*/
ehci->intr_unlinking = true;
while (ehci->intr_unlink) {
struct ehci_qh *qh = ehci->intr_unlink;
if (!stopped && qh->unlink_cycle == ehci->intr_unlink_cycle)
break;
ehci->intr_unlink = qh->unlink_next;
qh->unlink_next = NULL;
end_unlink_intr(ehci, qh);
}
/* Handle remaining entries later */
if (ehci->intr_unlink) {
ehci_enable_event(ehci, EHCI_HRTIMER_UNLINK_INTR, true);
++ehci->intr_unlink_cycle;
}
ehci->intr_unlinking = false;
}
/*
* Handler functions for the hrtimer event types.
* Keep this array in the same order as the event types indexed by
@ -200,6 +233,7 @@ static void ehci_disable_PSE(struct ehci_hcd *ehci)
static void (*event_handlers[])(struct ehci_hcd *) = {
ehci_poll_ASS, /* EHCI_HRTIMER_POLL_ASS */
ehci_poll_PSS, /* EHCI_HRTIMER_POLL_PSS */
ehci_handle_intr_unlinks, /* EHCI_HRTIMER_UNLINK_INTR */
ehci_disable_PSE, /* EHCI_HRTIMER_DISABLE_PERIODIC */
ehci_disable_ASE, /* EHCI_HRTIMER_DISABLE_ASYNC */
};

10
drivers/usb/host/ehci.h
View File

@ -81,6 +81,7 @@ enum ehci_rh_state {
enum ehci_hrtimer_event {
EHCI_HRTIMER_POLL_ASS, /* Poll for async schedule off */
EHCI_HRTIMER_POLL_PSS, /* Poll for periodic schedule off */
EHCI_HRTIMER_UNLINK_INTR, /* Wait for interrupt QH unlink */
EHCI_HRTIMER_DISABLE_PERIODIC, /* Wait to disable periodic sched */
EHCI_HRTIMER_DISABLE_ASYNC, /* Wait to disable async sched */
EHCI_HRTIMER_NUM_EVENTS /* Must come last */
@ -106,13 +107,16 @@ struct ehci_hcd { /* one per controller */
spinlock_t lock;
enum ehci_rh_state rh_state;
/* general schedule support */
unsigned scanning:1;
bool intr_unlinking:1;
/* async schedule support */
struct ehci_qh *async;
struct ehci_qh *dummy; /* For AMD quirk use */
struct ehci_qh *async_unlink;
struct ehci_qh *async_unlink_last;
struct ehci_qh *qh_scan_next;
unsigned scanning : 1;
unsigned async_count; /* async activity count */
/* periodic schedule support */
@ -123,6 +127,9 @@ struct ehci_hcd { /* one per controller */
unsigned i_thresh; /* uframes HC might cache */
union ehci_shadow *pshadow; /* mirror hw periodic table */
struct ehci_qh *intr_unlink;
struct ehci_qh *intr_unlink_last;
unsigned intr_unlink_cycle;
int next_uframe; /* scan periodic, start here */
unsigned periodic_count; /* periodic activity count */
unsigned uframe_periodic_max; /* max periodic time per uframe */
@ -385,6 +392,7 @@ struct ehci_qh {
struct ehci_qh *unlink_next; /* next on unlink list */
unsigned long unlink_time;
unsigned unlink_cycle;
unsigned stamp;
u8 needs_rescan; /* Dequeue during giveback */