dwc3.rst (1886B)
1=========== 2DWC3 driver 3=========== 4 5 6TODO 7~~~~ 8 9Please pick something while reading :) 10 11- Convert interrupt handler to per-ep-thread-irq 12 13 As it turns out some DWC3-commands ~1ms to complete. Currently we spin 14 until the command completes which is bad. 15 16 Implementation idea: 17 18 - dwc core implements a demultiplexing irq chip for interrupts per 19 endpoint. The interrupt numbers are allocated during probe and belong 20 to the device. If MSI provides per-endpoint interrupt this dummy 21 interrupt chip can be replaced with "real" interrupts. 22 - interrupts are requested / allocated on usb_ep_enable() and removed on 23 usb_ep_disable(). Worst case are 32 interrupts, the lower limit is two 24 for ep0/1. 25 - dwc3_send_gadget_ep_cmd() will sleep in wait_for_completion_timeout() 26 until the command completes. 27 - the interrupt handler is split into the following pieces: 28 29 - primary handler of the device 30 goes through every event and calls generic_handle_irq() for event 31 it. On return from generic_handle_irq() in acknowledges the event 32 counter so interrupt goes away (eventually). 33 34 - threaded handler of the device 35 none 36 37 - primary handler of the EP-interrupt 38 reads the event and tries to process it. Everything that requires 39 sleeping is handed over to the Thread. The event is saved in an 40 per-endpoint data-structure. 41 We probably have to pay attention not to process events once we 42 handed something to thread so we don't process event X prio Y 43 where X > Y. 44 45 - threaded handler of the EP-interrupt 46 handles the remaining EP work which might sleep such as waiting 47 for command completion. 48 49 Latency: 50 51 There should be no increase in latency since the interrupt-thread has a 52 high priority and will be run before an average task in user land 53 (except the user changed priorities).