requiried to keep consistent softc state before/after callback function
invocation and supposed to be sligntly faster than previous one as it
wouldn't incur callback overhead. With this change callback function
was gone.
- Decrease TI_MAXTXSEGS to 32 from 128. It seems that most mbuf chain
length is less than 32 and it would be re-packed with m_defrag(9) if
its chain length is larger than TI_MAXTXSEGS. This would protect ti(4)
against possible kernel stack overflow when txsegs[] is put on stack.
Alternatively, we can embed the txsegs[] into softc. However, that
would waste memory and make Tx/Rx speration hard when we want to
sperate Tx/Rx handlers to optimize locking.
- Fix dma map tracking used in Tx path. Previously it used the dma map
of the last mbuf chain in ti_txeof() which was incorrect as ti(4)
used dma map of the first mbuf chain when it loads a mbuf chain with
bus_dmamap_load_mbuf(9). Correct the bug by introducing queues that
keep track of active/inactive dma maps/mbuf chain.
- Use ti_txcnt to check whether driver need to set watchdog timer instead
of blidnly clearing the timer in ti_txeof().
- Remove the 3rd arg. of ti_encap(). Since ti(4) now caches the last
descriptor index(ti_tx_saved_prodidx) used in Tx there is no need to
pass it as a fuction arg.
- Change data type of producer/consumer index to int from u_int16_t in
order to remove implicit type conversions in Tx/Rx handlers.
- Check interface queue before getting a mbuf chain to reduce locking
overhead.
- Check number of available Tx descriptores to be 16 or higher in
ti_start(). This wouldn't protect Tx descriptor shortage but it would
reduce number of bus_dmamap_unload(9) calls in ti_encap() when we are
about to running out of Tx descriptors.
- Command NIC to send packets ony when the driver really has packets
enqueued. Previously it always set TI_MB_SENDPROD_IDX which would
command NIC to DMA Tx descriptors into NIC local memory regardless
of Tx descriptor changes.
Reviewed by: scottl
d2cea5305f