Re: Rate control & USB

[Helmut Schaa <helmut.schaa@googlemail.com>]

Am Dienstag 13 Juli 2010 schrieb Ivo Van Doorn:
> On Mon, Jul 12, 2010 at 9:14 PM, Helmut Schaa
> <helmut.schaa@googlemail.com> wrote:
> > Am Montag 12 Juli 2010 schrieb Ivo Van Doorn:
> >> I am currently looking into the old problem of the mac80211 rate
> >> control algorithms
> >> and USB devices. The Ralink USB devices (and as far as I know, the
> >> other USB devices
> >> as well), do not work well with the PID and Minstrel algorithms. This
> >> is caused by the
> >> fact that USB devices do not report the TX status to mac80211.
> >
> > Ivo, do you know by any chance if the USB devices also have a TX_STA_FIFO
> > register like the PCI variants? Does it contain useful data or just crap?
> 
> Well I guess he has the registers (we don't have rt2870 specific specsheets,
> but the register definitions from the original Ralink driver to
> suggest the register
> is there). However, even if it contains valid data, how do you want to match
> the contents of that register with the sent frames in the queue?

We could stuff a unique packet ID into the TXWI and the TX_STA_FIFO should
contain the same ID alongside the TX status after the frame was processed
by the hw.

> And another downside, is that the above only applies to rt2800usb, and not
> for rt73usb and rt2500usb, which neither have the TX status register, and were
> replaced with statistics registers (which I want to read for the batch
> TX status).

Ok, that's a valid argument ...

Helmut