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Please pick something while reading :)
- Convert interrupt handler to per-ep-thread-irq
As it turns out some DWC3-commands ~1ms to complete. Currently we spin
until the command completes which is bad.
- dwc core implements a demultiplexing irq chip for interrupts per
endpoint. The interrupt numbers are allocated during probe and belong
to the device. If MSI provides per-endpoint interrupt this dummy
interrupt chip can be replaced with "real" interrupts.
- interrupts are requested / allocated on usb_ep_enable() and removed on
usb_ep_disable(). Worst case are 32 interrupts, the lower limit is two
- dwc3_send_gadget_ep_cmd() will sleep in wait_for_completion_timeout()
until the command completes.
- the interrupt handler is split into the following pieces:
- primary handler of the device
goes through every event and calls generic_handle_irq() for event
it. On return from generic_handle_irq() in acknowledges the event
counter so interrupt goes away (eventually).
- threaded handler of the device
- primary handler of the EP-interrupt
reads the event and tries to process it. Everything that requires
sleeping is handed over to the Thread. The event is saved in an
We probably have to pay attention not to process events once we
handed something to thread so we don't process event X prio Y
where X > Y.
- threaded handler of the EP-interrupt
handles the remaining EP work which might sleep such as waiting
for command completion.
There should be no increase in latency since the interrupt-thread has a
high priority and will be run before an average task in user land
(except the user changed priorities).