Re: USB Host Controller driver for the MPC8270 processor

[Laurent Pinchart <laurentp@cse-semaphore.com>]

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Hi Huub,

On Thursday 29 May 2008 13:03, Huub Eikens wrote:
> Hi,
>  
> I am in need of a USB Host Controller device for the Freescale MPC8270 for
> the 2.4 linux kernel (ELDK 3.1.1). On internet I found one, but this is only
> for version 2.6:  
> http://cpm2usb.sourceforge.net/
> 
> I have a few options:
> 1. backport this driver to 2.4.25 kernel. I would like to know if this is
> feasible or not. I get the feeling that this will take a lot of time. 
> 2. upgrade my kernel to 2.6.x. This is not preferable for me since I depend
> on sw modules writen by external partners. If I upgrade, I really really
> need to be sure that this driver is stable and reliable.
> 3. Use an external USB Host Controller. Can anyone advise me on which
> controller to choose that runs stable and reliable on the 2.4.25 kernel
> (ELDK 3.1.1)?

I'd go for option 3. The CPM2 USB host controller is definitely not reliable. 
It relies on software to prepare SOF tokens, and doesn't do much in hardware.

After some experimentation with the FHCI driver posted on linux-ppc by  
Anton Vorontsov I found out that the driver would eat around 40% of my CPU 
time, and some SOF tokens would be incorrectly sent.

The CPM3 (aka QE) shouldn't have the same SOF issue, as it prepares SOF token 
without any software intervention, but I doubt it would perform much better 
in term of CPU time.

If you can go for an OHCI/UHCI/EHCI based controller that would be much 
better.

Best regards,

-- 
Laurent Pinchart
CSE Semaphore Belgium

Chaussee de Bruxelles, 732A
B-1410 Waterloo
Belgium

T +32 (2) 387 42 59
F +32 (2) 387 42 75

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