Based on kernel version 4.13.3. Page generated on 2017-09-23 13:56 EST.
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).