Documentation/usb/dwc3.txt

   1
   2  TODO
   3 ~~~~~~
   4 Please pick something while reading :)
   5
   6 - Convert interrupt handler to per-ep-thread-irq
   7
   8   As it turns out some DWC3-commands ~1ms to complete. Currently we spin
   9   until the command completes which is bad.
  10
  11   Implementation idea:
  12   - dwc core implements a demultiplexing irq chip for interrupts per
  13     endpoint. The interrupt numbers are allocated during probe and belong
  14     to the device. If MSI provides per-endpoint interrupt this dummy
  15     interrupt chip can be replaced with "real" interrupts.
  16   - interrupts are requested / allocated on usb_ep_enable() and removed on
  17     usb_ep_disable(). Worst case are 32 interrupts, the lower limit is two
  18     for ep0/1.
  19   - dwc3_send_gadget_ep_cmd() will sleep in wait_for_completion_timeout()
  20     until the command completes.
  21   - the interrupt handler is split into the following pieces:
  22     - primary handler of the device
  23       goes through every event and calls generic_handle_irq() for event
  24       it. On return from generic_handle_irq() in acknowledges the event
  25       counter so interrupt goes away (eventually).
  26
  27     - threaded handler of the device
  28       none
  29
  30     - primary handler of the EP-interrupt
  31       reads the event and tries to process it. Everything that requires
  32       sleeping is handed over to the Thread. The event is saved in an
  33       per-endpoint data-structure.
  34       We probably have to pay attention not to process events once we
  35       handed something to thread so we don't process event X prio Y
  36       where X > Y.
  37
  38     - threaded handler of the EP-interrupt
  39       handles the remaining EP work which might sleep such as waiting
  40       for command completion.
  41
  42   Latency:
  43    There should be no increase in latency since the interrupt-thread has a
  44    high priority and will be run before an average task in user land
  45    (except the user changed priorities).