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Diffstat (limited to 'kernel/Documentation/usb/dwc3.txt')
| -rw-r--r-- | kernel/Documentation/usb/dwc3.txt | 45 |
1 files changed, 45 insertions, 0 deletions
diff --git a/kernel/Documentation/usb/dwc3.txt b/kernel/Documentation/usb/dwc3.txt new file mode 100644 index 000000000..1d02c01d1 --- /dev/null +++ b/kernel/Documentation/usb/dwc3.txt @@ -0,0 +1,45 @@ + + TODO +~~~~~~ +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. + + Implementation idea: + - 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 + for ep0/1. + - 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 + none + + - 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 + per-endpoint data-structure. + 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. + + Latency: + 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). |