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SubjectRe: [patch 2.5] 2-pass PCI probing, generic part
On Fri, Jan 10, 2003 at 12:56:17AM -0700, Eric W. Biederman wrote:
> For what it is worth these cards exist though.


> Quadris cards have a 256MB bar, and dolphin cards default to having a 512MB bar.
> Both are high performance I/O adapters.

I'm not familiar with "dolphin" cards.
I'm aware of "Quadrics" but I've not heard anyone try those with parisc-linux.
Quadrics cards do work on ia64 (for some definition of "work").

> If someone leaves a big enough hole for hotplug cards I guess it can work...

Or dynamically assigns windows to PCI Bus controllers as PCI devices
are brought on-line. For PCI Hotplug, the role of managing MMIO/IRQ
resources has moved to the OS since these services are needed
after the OS has taken control of the box.

> How you define a potential boot device, and what it saves you to not assign
> it resources I don't know.

You have it backwards. firmware only assigns resources to boot devices
and "console" devices. ie firmware does minimal configuration.
Why? An OS with hotplug support can do it anyway.

A "potential boot device" has firmware support which the primary boot
loader can use to load the OS or a secondary boot loader. But firmware
only needs to configure a single boot/console device that is
actually being used.

> I am still recovering from putting a 256MB bar and 4GB of ram in a 4GB hole,
> with minimal loss on x86, so my imagination of what can be sanely done
> on a 64bit arch may be a little stunted..

both ia64 and later parisc boxes from HP reserve GB's of LMMIO address space
for IO uses (LMMIO == MMIO < 4GB). AFAIK, physical memory behind that address
space gets remapped to higher "physical" addresses by the memory controller.
But making 256MB still fit in that space can still be a challenge.
One 256MB BAR isn't so bad. It's when the customer wants to have a central
server that has 2 or more such cards...64-bit BARs on 64-bit architecture
make life alot easier.

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