Card-Reader Problem continued

[Christian Haul]

Alan Stern wrote:
> 
> I don't know of anything in the kernel that would cause these retries, 
> although it's possible that something in the sg driver is responsible.  
> It's also possible that the application is doing the retries.
> 
> Interestingly, the actual amount of work being done here seems to be the 
> same as on the other machine, and yet the total load is much lower.  I 
> have no idea why that should be.

Hi all,

looks like I have been prodding the wrong tree here. I've just managed
to open the machine and try all combinations of card readers and usb
ports. The "broken" machine showed absolutely the same broken behaviour
with the external card reader as with the internal reader.

It turned out that the internal card reader was not attached to the
on-board usb but an usb 2.0 extension card.

Testing against the on-board usb *both* card readers were *fine* and no
extra load was visible.
Testing against the usb 2.0 extension card, *both* readers caused a high
system load.

I did an additional test with two usb memory sticks: a 128MB usb 1.1 and
a 1GB usb 2.0 stick.

Attached to the on-board usb 1.1, both caused a "hi 2.0%" mark in top.
Attached to the usb 2.0 card, the usb 1.1 stick caused a "hi 10.0%" mark
and the usb 2.0 stick caused a "hi 2.0%" mark in top.

So, it really looks like a problem of the ehci driver with usb 1.1
devices. There are two kernel options I need to experiment with: the
"Full speed ISO transactions" and "Root Hub Translators", both marked
"experimental".

If I find something, I'll report back on the linux-usb list.

Alan, David, thank you very much indeed for your help and patience.
You're really great.

Cheers,
	Chris.