linux-kernel - Re: RapidIO - general questions

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Date:	Fri, 15 May 2009 09:33:11 +0200
From:	Jan Neskudla <jan.neskudla.ext@....com>
To:	ext Li Yang <leoli@...escale.com>
Cc:	linuxppc-dev <linuxppc-dev@...abs.org>,
	linux-kernel@...r.kernel.org
Subject: Re: RapidIO - general questions

On Wed, 2009-05-13 at 18:57 +0800, ext Li Yang wrote:
> cc'ed LKML
> 
> On Tue, May 12, 2009 at 5:17 PM, Jan Neskudla <jan.neskudla.ext@....com> wrote:
> > Hallo
> >
> > we'd likes to use a RapidIO as a general communication bus on our new
> > product, and so I have some questions about general design of Linux RIO
> > subsystem. I did not find any better mailing list for RapidIO
> > discussion.
> >
> > [1] - we'd like to implement following features
> >    * Hot-plug (hot-insert/hot-remove) of devices
> >    * Error handling (port-write packets - configuration, handling of
> > them)
> >    * Static ID configuration based on port numbers
> >    * Aux driver - basic driver, for sending messages over different
> > mboxes, handling ranges of doorbells
> >
> >    Is it here anyone who is working on any improvement, or anyone who
> > knows the development plans for RapidIO subsystem?
> >
> 
> AFAIK, there is no one currently working on these features for Linux.
> It will be good if you can add these useful features.
Yes it looks like that, currently we are analyzing current rapidIO
system, and how we can add these features. 

> 
> > [2] - I have a following problem with a current implementation of
> > loading drivers. The driver probe-function call is based on comparison
> > of VendorID (VID) and DeviceID (DID) only. Thus if I have 3 devices with
> > same DID and VID connected to the same network (bus), the driver is
> > loaded 3times, instead only once for the actual device Master port.
> 
> This should be the correct way as you actually have 3 instances of the device.
> 
> >
> > Rionet driver solved this by enabling to call initialization function
> > just once, and it expect that this is the Master port.
> 
> Rionet is kind of special.  It's not working like a simple device
> driver, but more like a customized protocol stack to support multiple
> ethernet over rio links.
> 
> >
> > Is it this correct behavior  ? It looks to me that RapidIO is handled
> > like a local bus (like PCI)
> 
> This is correct behavior.  All of them are using Linux device/driver
> infrastructure, but rionet is a special device.

But I do not have a 3 devices on one silicon. I am talking about 3
devices (3 x EP8548 boards + IDT switch) connected over rapidIO through
the switch. And in this case I'd like to have only one driver siting on
the top of Linux RapidIO subsystem. I don't see the advantage of loading
a driver locally for remote device. Am I missing something  ?

And one more think, I am getting so much Bus errors OOPSes. Whenever
there is a problem with a comunication over Rio I get such a kernel OPS.
I had to add some delays into some function to be able to finish the
enum+discovery process. Did you have some experience with some bigger
rio network running under linux ? 


                Jan 


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