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From: Laurent Pinchart <laurent.pinchart@tbox.biz>
To: Mike Rapoport <mike@compulab.co.il>
Subject: Re: CPM2 USB driver & MPC8248
Date: Tue, 7 Feb 2006 15:33:58 +0100
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> The driver development is stalled and I don't know when I'll be able to
> continue working on it.

Bad news, but I do understand. Please inform me when you will resume working 
on the driver, so that I can inform you of the progress I will have made (if 
any).

> >What are the major performance issues ?
>
> One of the issues in this driver is redunduncy between qe end ep
> structures and as a consequence a lot of uneeded code that make cross
> updates.
> I didn't run profiling, so I can't tell better.

Ok.

> >I noticed that the driver uses the MPC82xx packet level interface.
> >Why don't you use the transaction level interface ?
>
> The original driver I've started with used packet level. I thought on
> switching to transaction level, but I hadn't time for it because of
> other projects pressure.

Do you think it would be worth it, or are there any issue which you are aware 
of that would make it difficult/impractical/impossible/useless ?

> >That might explain why some devices don't even respond to the first
> > request. I noticed that, on my EP8248 board, the controller only sends
> > 990 SOF packets per second (or rather 990 SOF interrupts are generated).
> > I might have a time base problem somewhere, as I computed the number of
> > interrupts per second with a simple
> >
> >cat /proc/driver/m8xxhci_privateh > sof.1 && sleep 300 &&
> >cat /proc/driver/m8xxhci_privateh > sof.2
>
> I'm not sure such measurements are correct, since you sleep not exatly
> 300 seconds. I haven't measured how many SOF interrupts I get, but I
> think you maybe right.
> It may happen that during transmit or recieve the interrupts are off and
> SOF packets are not sent.

My bad, this was caused by the boot loader passing 66000000Hz instead of 
66666666Hz to Linux as the bus frequency. This is fixed now, and I get 1000 
SOF interrupts per second.

> >Do you have the same problem ? I'll see if I can get my hands on a USB
> >protocol analyzer.
>
> Good luck, I'll try to help but unfotunately I'm very much busy with
> other projects now.

Thanks for your help already.

Laurent Pinchart