multiple devices behind a cardbus bridge (adding magma pci extender support)

multiple devices behind a cardbus bridge (adding magma pci extender support)

[Mark Krischer]

[-- Attachment #1: Type: text/plain, Size: 1438 bytes --]

i'm trying to get the magma pci extender to work under linux.  basically,
this device is a bunch of external pci slots which connects to a laptop via
a cardbus pc card.  i've email david hinds, the maintainer of the linux
pcmcia, and he said that currently linux only supports adding a single
device behind a cardbus bridge.  he suggested that i check out the hot plug
stuff, saying you were providing a more generic interface.

(when i plugged the device in on the 2.2 and an early 2.4 kernel, btw, lspic
would detect the cardbus bridge.  i just couldn't see beyond it.)

any assistance on where to begin on this exercise would be greatly
appreciated.

thanks in advance.

--mk


----------------------------------------------------------------------------
----

Mark Krischer
Manager, Software Engineering
Wireless Networking Business Unit, Ethernet Access Group
Cisco Systems
P.O. Box 617, North Ryde 1670 AUSTRALIA
Level 2, 3 Innovation Road, Macquarie Research Park, North Ryde, NSW 2113
AUSTRALIA
Phone: +61 2 8446 1009    Fax: +61 2 8874 5401    Web: www.cisco.com

"I consider the terrorist attacks on September 11th to be an attack against
America's ideals.
If our freedoms erode because of those attacks, then the terrorists have
won."
— Bruce Schneier

"They that can give up essential liberty to obtain a little temporary safety
deserve neither liberty nor safety." — Benjamin Franklin


[-- Attachment #2: Type: text/html, Size: 4888 bytes --]

Re: multiple devices behind a cardbus bridge (adding magma pci

[David Brownell]

>    he said that currently linux only supports adding a single
> device behind a cardbus bridge.  

Is the root problem that drivers/pcmcia/cardbus.c
doesn't set up bridge devices when they're connected
to the Cardbus bridge?  Or is it perhaps that something
in drivers/pci/* isn't doing what's expected?

Once that bridge is hooked up, I'd expect it to hotplug
cards on that bus just like any other PCI device; that's
generic code.  The info I noticed at www.magma.com 
doesn't suggest you'd need to worry about the sort of
per-slot poweron/poweroff handshaking that designs
like "CompactPCI" or "Hotplug PCI" systems do.

- Dave



_______________________________________________
Linux-hotplug-devel mailing list  http://linux-hotplug.sourceforge.net
Linux-hotplug-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/linux-hotplug-devel

RE: multiple devices behind a cardbus bridge (adding magma pci extender support)

[Mark Krischer]

i believe it's the former.  though i'm still tracing through the code.  it
looks like the new yenta.c is what's used now?  i had to return my magma pci
extender and won't be getting new ones until the end of next week.  so i
guess i'm trying to get an idea of where i should start playing when i start
next week.

my understanding was not so much that i needed the hot-plug specific stuff,
but rather whatever new pci support you've added.  but i could be on the
wrong path here.

thanks.

--mk

> -----Original Message-----
> From: David Brownell [mailto:david-b@pacbell.net]
> Sent: Thursday, 4 October 2001 11:11 AM
> To: Mark Krischer; linux-hotplug-devel@lists.sourceforge.net
> Subject: Re: multiple devices behind a cardbus bridge (adding magma pci
> extender support)
>
>
> >    he said that currently linux only supports adding a single
> > device behind a cardbus bridge.
>
> Is the root problem that drivers/pcmcia/cardbus.c
> doesn't set up bridge devices when they're connected
> to the Cardbus bridge?  Or is it perhaps that something
> in drivers/pci/* isn't doing what's expected?
>
> Once that bridge is hooked up, I'd expect it to hotplug
> cards on that bus just like any other PCI device; that's
> generic code.  The info I noticed at www.magma.com
> doesn't suggest you'd need to worry about the sort of
> per-slot poweron/poweroff handshaking that designs
> like "CompactPCI" or "Hotplug PCI" systems do.
>
> - Dave
>
>
>


_______________________________________________
Linux-hotplug-devel mailing list  http://linux-hotplug.sourceforge.net
Linux-hotplug-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/linux-hotplug-devel

Re: multiple devices behind a cardbus bridge (adding magma pci extender support)

[David Hinds]

On Wed, Oct 03, 2001 at 06:10:42PM -0700, David Brownell wrote:
> 
> Is the root problem that drivers/pcmcia/cardbus.c
> doesn't set up bridge devices when they're connected
> to the Cardbus bridge?

This is it.  The cardbus code will configure a single normal device on
the far side of the cardbus bridge, not (potentially) a whole tree of
things.  It is similar to the hot plug PCI situation.

-- Dave

_______________________________________________
Linux-hotplug-devel mailing list  http://linux-hotplug.sourceforge.net
Linux-hotplug-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/linux-hotplug-devel

Re: multiple devices behind a cardbus bridge (adding magma pci extender support)

[Greg KH]

On Wed, Oct 03, 2001 at 09:18:54PM -0700, David Hinds wrote:
> On Wed, Oct 03, 2001 at 06:10:42PM -0700, David Brownell wrote:
> > 
> > Is the root problem that drivers/pcmcia/cardbus.c
> > doesn't set up bridge devices when they're connected
> > to the Cardbus bridge?
> 
> This is it.  The cardbus code will configure a single normal device on
> the far side of the cardbus bridge, not (potentially) a whole tree of
> things.  It is similar to the hot plug PCI situation.

But for hotplug PCI, you need a hotplug pci controller that handles the
initialization of that pci tree (among other things).  For this device,
does it have a controller that can be addressed to do these things?

thanks,

greg k-h

_______________________________________________
Linux-hotplug-devel mailing list  http://linux-hotplug.sourceforge.net
Linux-hotplug-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/linux-hotplug-devel

Re: multiple devices behind a cardbus bridge (adding magma pci extender support)

[David Hinds]

On Thu, Oct 04, 2001 at 08:24:05AM -0700, Greg KH wrote:
> 
> But for hotplug PCI, you need a hotplug pci controller that handles the
> initialization of that pci tree (among other things).  For this device,
> does it have a controller that can be addressed to do these things?

What do you mean by "handles the initialization"?  A hot plug PCI
controller mainly gives control over power sequencing and isolation of
the PCI devices behind the controller from the rest of the PCI tree,
right?  I'd think that this product would have to provide the same
functionality.

-- Dave

_______________________________________________
Linux-hotplug-devel mailing list  http://linux-hotplug.sourceforge.net
Linux-hotplug-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/linux-hotplug-devel

Re: multiple devices behind a cardbus bridge (adding magma pci extender support)

[Greg KH]

On Thu, Oct 04, 2001 at 08:37:39AM -0700, David Hinds wrote:
> On Thu, Oct 04, 2001 at 08:24:05AM -0700, Greg KH wrote:
> > 
> > But for hotplug PCI, you need a hotplug pci controller that handles the
> > initialization of that pci tree (among other things).  For this device,
> > does it have a controller that can be addressed to do these things?
> 
> What do you mean by "handles the initialization"?  A hot plug PCI
> controller mainly gives control over power sequencing and isolation of
> the PCI devices behind the controller from the rest of the PCI tree,
> right?  I'd think that this product would have to provide the same
> functionality.

Yes, you are correct.  That's what I was trying to say.

thanks,

greg k-h

_______________________________________________
Linux-hotplug-devel mailing list  http://linux-hotplug.sourceforge.net
Linux-hotplug-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/linux-hotplug-devel

Re: multiple devices behind a cardbus bridge (adding magma pci

[David Brownell]

> > > But for hotplug PCI, you need a hotplug pci controller that handles the
> > > initialization of that pci tree (among other things).  For this device,
> > > does it have a controller that can be addressed to do these things?
> > 
> > What do you mean by "handles the initialization"?  A hot plug PCI
> > controller mainly gives control over power sequencing and isolation of
> > the PCI devices behind the controller from the rest of the PCI tree,
> > right?  I'd think that this product would have to provide the same
> > functionality.
> 
> Yes, you are correct.  That's what I was trying to say.

Not all PCI bridges have per-slot power control over devices
connected to them though, do they?

I was under the strong impression that most didn't, and that
CompactPCI/HotplugPCI/Cardbus/... were the exceptions
to the rule.  And that these Magma extenders were likely
pretty standard -- the pictures I saw didn't show any of the
special hardware I've seen on HotplugPCI rackmounts, etc.

I guess it all comes down to needing more info about the Magma
card.  Also a potential confusion about what "Hotplug" means;
at one level it's a particular implementation of power switching
on PCI (CompactPCI and Cardbus being others), and at another
level it's a generic feature of the Linux PCI support that fires
automatically for all correctly configured devices (assuming it's
been configured in).

- Dave



_______________________________________________
Linux-hotplug-devel mailing list  http://linux-hotplug.sourceforge.net
Linux-hotplug-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/linux-hotplug-devel

Re: multiple devices behind a cardbus bridge (adding magma pci extender support)

[David Hinds]

On Thu, Oct 04, 2001 at 10:40:25AM -0700, David Brownell wrote:

> > > What do you mean by "handles the initialization"?  A hot plug PCI
> > > controller mainly gives control over power sequencing and isolation of
> > > the PCI devices behind the controller from the rest of the PCI tree,
> > > right?  I'd think that this product would have to provide the same
> > > functionality.
> > 
> > Yes, you are correct.  That's what I was trying to say.
> 
> Not all PCI bridges have per-slot power control over devices
> connected to them though, do they?

Certainly.

The PCI-to-PCI bridge in the Magma device may well be an ordinary one
that provides no per-slot power control.  However, the fact that it is
sitting behind a cardbus bridge that does provide hot plug power
control, means that as far as the kernel is concerned, this is an
instance of the "general" PCI hot plug configuration problem (more
like Hot Plug PCI or Compact PCI), which is fairly complex from a
resource allocation perspective, as opposed to the "narrow" PCI hot
plug problem that is currently addressed by the simple CardBus
one-PCI-device configuration system.

-- Dave

_______________________________________________
Linux-hotplug-devel mailing list  http://linux-hotplug.sourceforge.net
Linux-hotplug-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/linux-hotplug-devel