1) Use the TX FIFO empty interrupts to poll the transmit FIFO usage,
instead of using own software counters and waiting for SOF
interrupts. Assume that enough FIFO space is available to execute one
USB OUT transfer of any kind when the TX FIFO is empty.
2) Use the host channel halted event to asynchronously wait for host
channels to be disabled instead of waiting for SOF interrupts. This
results in less turnaround time for re-using host channels and at the
same time increases the performance.
The network transmit performance measured by "iperf" for the "RPi-B v1
2011/12" board, increased from 45MBit/s to 65Mbit/s after applying the
changes above.
No regressions seen using:
- High Speed (BULK, CONTROL, INTERRUPT)
- Full Speed (All transfer types)
- Low Speed (Control and Interrupt)
MFC after: 1 month
Submitted by: Daisuke Aoyama <aoyama@peach.ne.jp>
a529288d65