GSPI and SDIO performance for 8686

[Tim Harvey]

Dan Williams wrote:
> On Wed, 2009-07-29 at 09:59 -0700, Tim Harvey 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?
>>
>> 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)?
>>     
>
> Any horrible SDIO performance you've seen has got to be dependent on
> either HZ or the SDHC.  I've routinely pulled 11 or 12 Mbps with normal
> laptop Ricoh R5C822 controllers.  Now maybe there's scheduling latency
> or something in the libertas code that erroneously ratelimits related to
> HZ, but we know we can pull respectable rates out of the card if the
> SDHC doesn't suck.  So we've got a baseline.  At this point, I suspect
> the host controller and platform code more than I suspect the libertas
> driver or the 8686 chip/firmware given this baseline.
>
> Dan
>
>
>   

I would agree the horrible SDIO performance is related to SDHC.  The 
only people claiming ~10mbps have been using the PCI based Richoh 
SDHCI.  Has anyone seen > ~1.5mbps using SDIO on any ARM platform?   The 
i.MX31 SDHC I tesed a year ago was severely limited - only would do 1bit 
SDIO and required 4-byte algined transfers.  The beagleboard I tested 
about 6 months ago with the OMAP3x SDHC would apparently do 4-bit SDIO 
but still showed the same performance.

Tim

Tim