USB: OHCI avoids root hub timer polling

This teaches OHCI to use the root hub status change (RHSC) IRQ, bypassing
root hub timers most of the time and switching over to the "new" root hub
polling scheme.  It's complicated by the fact that implementations of OHCI
trigger and ack that IRQ differently (the spec is vague there).

Avoiding root hub timers helps mechanisms like "dynamic tick" leave the
CPU in lowpower modes for longer intervals.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 5 insertions, 0 deletions

diff --git a/drivers/usb/host/ohci-dbg.c b/drivers/usb/host/ohci-dbg.c
index 7bfffcbbd226..da52609a9290 100644
--- a/drivers/usb/host/ohci-dbg.c
+++ b/drivers/usb/host/ohci-dbg.c
@@ -667,6 +667,11 @@ show_registers (struct class_device *class_dev, char *buf)
         size -= temp;
         next += temp;
 
+        temp = scnprintf (next, size, "hub poll timer %s\n",
+                        ohci_to_hcd(ohci)->poll_rh ? "ON" : "off");
+        size -= temp;
+        next += temp;
+
         /* roothub */
         ohci_dump_roothub (ohci, 1, &next, &size);