[PATCH] UHCI: use integer-sized frame numbers

This patch (as687) changes uhci-hcd to keep track of frame numbers as
full-sized integers rather than 11-bit values.  This makes them a lot
easier to handle and makes it possible to schedule beyond a 2-second
window, should anyone ever want to do so.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 22 insertions, 18 deletions

diff --git a/drivers/usb/host/uhci-hcd.c b/drivers/usb/host/uhci-hcd.c
index 395402eec5ef..5e75ad6dc29f 100644
--- a/drivers/usb/host/uhci-hcd.c
+++ b/drivers/usb/host/uhci-hcd.c
@@ -13,7 +13,7 @@
  * (C) Copyright 2000 Yggdrasil Computing, Inc. (port of new PCI interface
  *               support from usb-ohci.c by Adam Richter, adam@yggdrasil.com).
  * (C) Copyright 1999 Gregory P. Smith (from usb-ohci.c)
- * (C) Copyright 2004-2005 Alan Stern, stern@rowland.harvard.edu
+ * (C) Copyright 2004-2006 Alan Stern, stern@rowland.harvard.edu
  *
  * Intel documents this fairly well, and as far as I know there
  * are no royalties or anything like that, but even so there are
@@ -31,7 +31,6 @@
 #include <linux/ioport.h>
 #include <linux/sched.h>
 #include <linux/slab.h>
-#include <linux/smp_lock.h>
 #include <linux/errno.h>
 #include <linux/unistd.h>
 #include <linux/interrupt.h>
@@ -146,7 +145,8 @@ static void configure_hc(struct uhci_hcd *uhci)
         outl(uhci->frame_dma_handle, uhci->io_addr + USBFLBASEADD);
 
         /* Set the current frame number */
-        outw(uhci->frame_number, uhci->io_addr + USBFRNUM);
+        outw(uhci->frame_number & UHCI_MAX_SOF_NUMBER,
+                        uhci->io_addr + USBFRNUM);
 
         /* Mark controller as not halted before we enable interrupts */
         uhci_to_hcd(uhci)->state = HC_STATE_SUSPENDED;
@@ -239,7 +239,6 @@ __acquires(uhci->lock)
                 dev_warn(uhci_dev(uhci), "Controller not stopped yet!\n");
 
         uhci_get_current_frame_number(uhci);
-        smp_wmb();
 
         uhci->rh_state = new_state;
         uhci->is_stopped = UHCI_IS_STOPPED;
@@ -253,7 +252,6 @@ static void start_rh(struct uhci_hcd *uhci)
 {
         uhci_to_hcd(uhci)->state = HC_STATE_RUNNING;
         uhci->is_stopped = 0;
-        smp_wmb();
 
         /* Mark it configured and running with a 64-byte max packet.
          * All interrupts are enabled, even though RESUME won't do anything.
@@ -360,12 +358,21 @@ static irqreturn_t uhci_irq(struct usb_hcd *hcd, struct pt_regs *regs)
 
 /*
  * Store the current frame number in uhci->frame_number if the controller
- * is runnning
+ * is runnning.  Expand from 11 bits (of which we use only 10) to a
+ * full-sized integer.
+ *
+ * Like many other parts of the driver, this code relies on being polled
+ * more than once per second as long as the controller is running.
  */
 static void uhci_get_current_frame_number(struct uhci_hcd *uhci)
 {
-        if (!uhci->is_stopped)
-                uhci->frame_number = inw(uhci->io_addr + USBFRNUM);
+        if (!uhci->is_stopped) {
+                unsigned delta;
+
+                delta = (inw(uhci->io_addr + USBFRNUM) - uhci->frame_number) &
+                                (UHCI_NUMFRAMES - 1);
+                uhci->frame_number += delta;
+        }
 }
 
 /*
@@ -798,18 +805,15 @@ done:
 static int uhci_hcd_get_frame_number(struct usb_hcd *hcd)
 {
         struct uhci_hcd *uhci = hcd_to_uhci(hcd);
-        unsigned long flags;
-        int is_stopped;
-        int frame_number;
+        unsigned frame_number;
+        unsigned delta;
 
         /* Minimize latency by avoiding the spinlock */
-        local_irq_save(flags);
-        is_stopped = uhci->is_stopped;
-        smp_rmb();
-        frame_number = (is_stopped ? uhci->frame_number :
-                        inw(uhci->io_addr + USBFRNUM));
-        local_irq_restore(flags);
-        return frame_number;
+        frame_number = uhci->frame_number;
+        barrier();
+        delta = (inw(uhci->io_addr + USBFRNUM) - frame_number) &
+                        (UHCI_NUMFRAMES - 1);
+        return frame_number + delta;
 }
 
 static const char hcd_name[] = "uhci_hcd";