the length of frame should be treated as multiple of 4. Actual
frame length is set in the TX header. The TX header position
should be aligned on 4 byte boundary and actual frame start
position should be aligned on 4 byte boundary as well. This means
we need 4(TX header length) + 3(frame length fixup) additional free
space in TX buffer in addition to actual frame length.
Make sure TX handler check these additional bytes.
ae_tx_avail_size() returns actual free space in TX buffer to ease
the calculation of available TX buffer space in caller. While I'm
here, replace magic number to appropriate sizeof operator to
enhance readability.
This change should fix controller lockup issue happened under
certain conditions but it still does not fix watchdog timeout. It
seems the watchdog timeout is side-effect of TxS and TxD
mismatches. The root cause of TxD/TxD mismatch is not known yet but
it looks like silicon bug. I guess driver may have to reinitialize
controller whenever it sees TxS and TxD mismatches but leave it as
it was at this moment.
PR: kern/145918
e18783345a