mirror of
https://mirrors.bfsu.edu.cn/git/linux.git
synced 2024-12-01 08:04:22 +08:00
ecefae6db0
While there are a mix of things here, most of the stuff were written from Kernel developer's PoV. So, add them to the driver-api book. A follow up for this patch would be to move documents from there that are specific to sysadmins, adding them to the admin-guide. Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org> Acked-by: Johan Hovold <johan@kernel.org> Acked-by: Felipe Balbi <felipe.balbi@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
54 lines
1.8 KiB
ReStructuredText
54 lines
1.8 KiB
ReStructuredText
===========
|
|
DWC3 driver
|
|
===========
|
|
|
|
|
|
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).
|