path: root/drivers/usb/host/ehci-timer.c
diff options
authorAlan Stern <stern@rowland.harvard.edu>2012-07-11 11:23:00 -0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2012-07-16 16:56:47 -0700
commit569b394f53f0abd177cc665c9b4ace89e3f4c7fb (patch)
tree030ce9c94e724f713155ffacc7caab7f459e9b96 /drivers/usb/host/ehci-timer.c
parent361aabf395e4a23cf554cf4ec0c0c6963b8beb01 (diff)
USB: EHCI: always scan each interrupt QH
This patch (as1585) fixes a bug in ehci-hcd's scheme for scanning interrupt QHs. Currently a single routine takes care of scanning everything on the periodic schedule. Whenever an interrupt occurs, it scans all isochronous and interrupt URBs scheduled for frames that have elapsed since the last scan. This has two disadvantages. The first is relatively minor: An interrupt QH is likely to end up getting scanned multiple times, particularly if the last scan was not fairly recent. (The current code avoids this by maintaining a periodic_stamp in each interrupt QH.) The second is more serious. The periodic schedule wraps around. If the last scan occurred during frame N, and the next scan occurs when the schedule has gone through an entire cycle and is back at frame N, the scanning code won't look at any frames other than N. Consequently it won't see any QHs that completed during frame N-1 or earlier. The patch replaces the entire frame-based approach for scanning interrupt QHs with a new routine using a list-based approach, the same as for async QHs. This has a slight disadvantage, because it means that all interrupt QHs have to be scanned every time. But it is more robust than the current approach. 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-timer.c')
1 files changed, 1 insertions, 6 deletions
diff --git a/drivers/usb/host/ehci-timer.c b/drivers/usb/host/ehci-timer.c
index a823290b5139..0e28bae78d18 100644
--- a/drivers/usb/host/ehci-timer.c
+++ b/drivers/usb/host/ehci-timer.c
@@ -168,13 +168,8 @@ static void ehci_poll_PSS(struct ehci_hcd *ehci)
/* The status is up-to-date; restart or stop the schedule as needed */
if (want == 0) { /* Stopped */
- if (ehci->periodic_count > 0) {
- /* make sure ehci_work scans these */
- ehci->next_uframe = ehci_read_frame_index(ehci)
- & ((ehci->periodic_size << 3) - 1);
+ if (ehci->periodic_count > 0)
ehci_set_command_bit(ehci, CMD_PSE);
- }
} else { /* Running */
if (ehci->periodic_count == 0) {