GSPI and SDIO performance for 8686

[Andrey Yurovsky]

On Wed, Jul 29, 2009 at 9:59 AM, Tim Harvey<tharvey at irobot.com> wrote:
> Greetings,
>
> I've seen a lot of activity lately and development of the GSPI interface for
> libertas.  What max throughput have people been able to get with an 8686
> talking over GSPI?

We typically see 10mpbs UDP / 7mbps TCP with GSPI on Blackfin, and we
can get higher throughput when using a different SPI host controller.
I posted an RFC patch a while back that will further improve
throughput (and simplify the driver) but it needs more work, for now
throughput is reasonable but there's definitely room for improvement.

> My previous evaluation with an 8686 talking over SDIO (both to an i.MX31
> SDHC on a patched 2.6.22 and to an OMAP3x SDHC on 2.6.28 beagleboard) showed
> a horribly slow max throughput of about 1.4mbps.  Has anyone seen better
> performance in recent libertas/kernel with the OMAP3x SDHC (ie talking to
> the 8686 on an Overo Fire/Air)?

We've seen 21mpbs UDP and about 19mbps TCP on a ThinkPad with the
Richoh SDHCI controller.  1.4mbps seems suspicious to me, perhaps it's
a host controller issue?

  -Andrey