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>

1 files changed, 5 insertions, 3 deletions

diff --git a/drivers/usb/host/ehci.h b/drivers/usb/host/ehci.h
index c462d52ac575..08637183aad0 100644
--- a/drivers/usb/host/ehci.h
+++ b/drivers/usb/host/ehci.h
@@ -117,6 +117,7 @@ struct ehci_hcd {			/* one per controller */
         bool                    need_rescan:1;
         bool                    intr_unlinking:1;
         bool                    async_unlinking:1;
+        struct ehci_qh          *qh_scan_next;
 
         /* async schedule support */
         struct ehci_qh          *async;
@@ -124,7 +125,6 @@ struct ehci_hcd {			/* one per controller */
         struct ehci_qh          *async_unlink;
         struct ehci_qh          *async_unlink_last;
         struct ehci_qh          *async_iaa;
-        struct ehci_qh          *qh_scan_next;
         unsigned                async_unlink_cycle;
         unsigned                async_count;    /* async activity count */
 
@@ -133,6 +133,7 @@ struct ehci_hcd {			/* one per controller */
         unsigned                periodic_size;
         __hc32                  *periodic;      /* hw periodic table */
         dma_addr_t              periodic_dma;
+        struct list_head        intr_qh_list;
         unsigned                i_thresh;       /* uframes HC might cache */
 
         union ehci_shadow       *pshadow;       /* mirror hw periodic table */
@@ -140,6 +141,8 @@ struct ehci_hcd {			/* one per controller */
         struct ehci_qh          *intr_unlink_last;
         unsigned                intr_unlink_cycle;
         int                     next_uframe;    /* scan periodic, start here */
+        unsigned                intr_count;     /* intr activity count */
+        unsigned                isoc_count;     /* isoc activity count */
         unsigned                periodic_count; /* periodic activity count */
         unsigned                uframe_periodic_max; /* max periodic time per uframe */
 
@@ -176,7 +179,6 @@ struct ehci_hcd {			/* one per controller */
 
         struct timer_list       watchdog;
         unsigned long           actions;
-        unsigned                periodic_stamp;
         unsigned                random_frame;
         unsigned long           next_statechange;
         ktime_t                 last_periodic_enable;
@@ -381,11 +383,11 @@ struct ehci_qh {
         dma_addr_t              qh_dma;         /* address of qh */
         union ehci_shadow       qh_next;        /* ptr to qh; or periodic */
         struct list_head        qtd_list;       /* sw qtd list */
+        struct list_head        intr_node;      /* list of intr QHs */
         struct ehci_qtd         *dummy;
         struct ehci_qh          *unlink_next;   /* next on unlink list */
 
         unsigned                unlink_cycle;
-        unsigned                stamp;
 
         u8                      needs_rescan;   /* Dequeue during giveback */
         u8                      qh_state;