[Gta04-owner] Small update to 3.7-gta04 kernel: faster wifi.

[Andreas Kemnade]

Hi,

On Sat, 19 Oct 2013 11:13:15 +0200
"Neal H. Walfield" <neal at walfield.org> wrote:

> At Fri, 18 Oct 2013 20:44:22 +1100,
> NeilBrown wrote:
> > I've just pushed out a small update to 3.7-gta04.
> > 
> > This update adds support for the IRQ line from SDIO cards, such as the wifi
> > in the gta04.
> > This allows the wifi to go faster.
> > With polling (the old behaviour) I get about 1Mb/sec
> > With Interupts enabled and polling disabled I get about 4Mb/sec.
> > If I have interrupts *and* polling (which admittedly is a strange
> > config to even try) I get 5Mb/sec on my 800MHz board, and 6Mb/sec on
> > my 1GHz board.
> > 
> > So the code currently does both.  It is a bit of a hack (and not the only
> > hack) but it works OK for now.
> 
> I don't know how these two config options interact.  For what it is
> worth, polling often has lower overhead than processing an interrupt
> if there is data waiting.  The tradeoff is that if there is no data
> waiting, then polling slightly potentially increases latency and burns
> a significant amount of CPU cycles.  Thus, some device drivers will
> switch to polling mode when it appears that a lot of data will arrive
> and revert to interrupts when the throughput dips below some
> threshold.  Perhaps this is what the two config options are enabling.
> 
Hmm, in that 2.6.32-hw-validation kernel, the interrupt mode works
alone with highspeed (no polling). Somehow some interrupts are lost now,
so I did not disable the polling.
I guess, polling would be better at much higher data rates, but not at
that low data rates we have here.

Greetings
Andreas Kemnade
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