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

[Neal H. Walfield]

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.

Neal