I was going to say that eepro100's speedo_rx_link() does the same DMA
abuse as e100, but then I noticed one little detail: eepro100 sets both
EL (end of list) and S (suspend) bits in the RFD as it chains it to the
RFD list. e100 was only setting the EL bit. Hmmm, that's interesting.
That means that if HW reads a RFD with the S-bit set, it'll process
that RFD and then suspend the receive unit. The receive unit will
resume when SW clears the S-bit. There is no need for SW to restart
the receive unit. Which means a lot of the receive unit state tracking
code in the driver goes away.
So here's a patch against 2.6.14. (Sorry for inlining it; the mailer
I'm using now will mess with the word wrap). I can't test this on
XScale (unless someone has an e100 module for Gumstix :) . It should
be doing exactly what eepro100 does with RFDs. I don't believe this
change will introduce a performance hit because the S-bit and EL-bit go
hand-in-hand meaning if we're going to suspend because of the S- bit,
we're on the last resource anyway, so we'll have to wait for SW to
replenish.
(cherry picked from 29e79da9495261119e3b2e4e7c72507348e75976 commit)
d52df4a35a