Lower the timer freq if no iso schedule packets complete for 64 frames in
a row.
We can safely do this, without adding latency, because:
1) If there is isoc traffic this will never trigger
2) For async handled interrupt packets (only usb-host), the completion handler
will immediately schedule the frame_timer from a bh
3) All devices using NAK to signal no data for interrupt endpoints now use
wakeup, which will immediately schedule the frame_timer from a bh
The advantage of this is that when we only have interrupt packets in the
periodic schedule, async_stepdown can do its work and significantly lower
the frequency at which the frame_timer runs.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
