Diffstat (limited to 'Documentation/usb')
1 files changed, 53 insertions, 0 deletions
diff --git a/Documentation/usb/dwc3.txt b/Documentation/usb/dwc3.txt
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+Please pick something while reading :)
+- Implement streaming support for BULK endpoints
+ Tatyana's patch "usb: Add streams support to the gadget framework"
+ introduces streaming support for the gadget driver.
+ Every usb_request has new field called stream_id which holds its id.
+ Every usb_ep has a field num_supported_strms which describes the max
+ number of streams supported (for this ep).
+ UAS is AFAIK the only gadget with streaming support.
+- 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
+ - primary handler of the EP-interrupt
+ reads the event and tries to process it. Everything that requries
+ 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.
+ 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).