Recommended FIFO allocation schema includes 2 maximum endpoint sizes.
Comment suggested that this is the case while it would work according
to this description only in checked endpoints were ascending sizes.
Also two same size endpoints would be counted as one.
That is fixed by way sz is filled.
Calculation used too much modulo operation while single division was enough
to account for odd FIFO sizes.
Extra space that is evenly distributed between Bulk and control endpoints
was incorrectly calculated it could prevent allocation of ISO endpoint FIFO
when bulk endpoints existed with smaller endpoint numbers.
Minimum endpoint FIFO size is 16 32bit words, FIFO space requirement is
now observed.
Endpoint close was implemented only in one driver so far.
This function is needed for interfaces with several alternate settings.
The way FIFO is allocated in dcd_edpt_open() allows to correctly close
only one IN endpoint (the one that was opened last).
Wrong FIFO was flushed in dcd_edpt_stall().
(epnum - 1) should only be used when accessing DIEPTXF registers.
For DIEPCTL and GRSTCTL epnum is correct index.
For ISO endpoint driver has to specify when data
is to be transmitted (odd or even frame).
Currently code was not updating this bit resulting in
data being sent every other frame.
If interval was 1ms full data packed was sent every 2ms, and
ZLP was sent in between.
In some rare ocasions (bad cable, noise, etc.) data transfer might timeout and hang the endpoint, unless the interrupt flag is cleared.
This pull request targets to solve that case.
While the ST code has a 2 ms stabilization delay for the USBC PHY PLL,
running without this delay showed no problem for at leat 10 USB un/replug
cycles. Observe for problems!
ESP32-S2 has only 5 available endpoint-in FIFOs (including EP0) but 7 available EP IN numbers. This change decouples the fifo number from the endpoint number, providing FIFO numbers until they reach the limit, at which point it will return false and assert an error that too many endpoints were allocated.
Jerzy Kasenberg