diff options
| author | Alan Stern <stern@rowland.harvard.edu> | 2012-07-11 11:22:35 -0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2012-07-16 16:54:25 -0700 |
| commit | 55934eb3b9fa52eb53b9d7342267fc73c38206aa (patch) | |
| tree | 66666fa4f08121a53152cb956a6ef36026edc057 /drivers/usb/host/ehci.h | |
| parent | bf6387bcd16975ba8952b094f262a359d74e1c8a (diff) | |
USB: EHCI: use hrtimer for (s)iTD deallocation
This patch (as1579) adds an hrtimer event to handle deallocation of
iTDs and siTDs in ehci-hcd.
Because of the frame-oriented approach used by the EHCI periodic
schedule, the hardware can continue to access the Transfer Descriptor
for isochronous (or split-isochronous) transactions for up to a
millisecond after the transaction completes. The iTD (or siTD) must
not be reused before then.
The strategy currently used involves putting completed iTDs on a list
of cached entries and every so often returning them to the endpoint's
free list. The new strategy reduces overhead by putting completed
iTDs back on the free list immediately, although they are not reused
until it is safe to do so.
When the isochronous endpoint stops (its queue becomes empty), the
iTDs on its free list get moved to a global list, from which they will
be deallocated after a minimum of 2 ms. This delay is what the new
hrtimer event is for.
Overall this may not be a tremendous improvement over the current
code, but to me it seems a lot more clear and logical. In addition,
it removes the need for each iTD to keep a reference to the
ehci_iso_stream it belongs to, since the iTD never needs to be moved
back to the stream's free list from the global list.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/usb/host/ehci.h')
| -rw-r--r-- | drivers/usb/host/ehci.h | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/drivers/usb/host/ehci.h b/drivers/usb/host/ehci.h index 6874d89b0b64..bcfbb175e2b4 100644 --- a/drivers/usb/host/ehci.h +++ b/drivers/usb/host/ehci.h @@ -83,6 +83,7 @@ enum ehci_hrtimer_event { EHCI_HRTIMER_POLL_PSS, /* Poll for periodic schedule off */ EHCI_HRTIMER_POLL_DEAD, /* Wait for dead controller to stop */ EHCI_HRTIMER_UNLINK_INTR, /* Wait for interrupt QH unlink */ + EHCI_HRTIMER_FREE_ITDS, /* Wait for unused iTDs and siTDs */ 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 */ @@ -139,7 +140,9 @@ struct ehci_hcd { /* one per controller */ /* list of itds & sitds completed while clock_frame was still active */ struct list_head cached_itd_list; + struct ehci_itd *last_itd_to_free; struct list_head cached_sitd_list; + struct ehci_sitd *last_sitd_to_free; unsigned clock_frame; /* per root hub port */ @@ -250,8 +253,6 @@ timer_action_done (struct ehci_hcd *ehci, enum ehci_timer_action action) clear_bit (action, &ehci->actions); } -static void free_cached_lists(struct ehci_hcd *ehci); - /*-------------------------------------------------------------------------*/ #include <linux/usb/ehci_def.h> |